bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrolysis of O2-Containing Low Concentration CO2 in Solid Oxide Electrolysis Cells with La-Based Hexaaluminate Cathode for Syngas Production
Authors: Sun Xueyan , Zhao Wei , Zhu Liangliang , Shui Ziyi , Chen Xi , Zhu Yanyan
Published: May 2020

Excessive emission of CO2, the primary greenhouse gas, has been widely believed to be the main contributor to global warming. Recently, direct-air-capture (DAC) of CO2 is emerging as a promising technique to mitigate the greenhouse problem. In this work, a new technology is developed where the CO2/air mixture captured by DAC1 is directly converted into high value-added syngas using solid oxide electrolysis cells (SOECs)2. In this new system, H2O and O2-containing CO2 (CO2/air mixture) are co-electrolyzed for syngas production in the cathode of SOECs, and in the anode, methane is partially oxidized into syngas to decrease the overpotential and electricity consumption.

The cathode materials of SOECs need to keep stable under the condition of strong reduction and high humidity. meanwhile CO2 directly captured from ambient air is mixed with oxygen in the cathode, which poses a challenge to prevent the oxidation of cathode materials. Hexaaluminate3 (AAl12O19-δ or AAl12O17-δ), as a kind of composite metal oxides, is considered as one of the most promising high-temperature catalytic materials due to its unique layered crystal structure. Besides, Al3+ in its structure can be partially or completely substituted by transition metal ions, and the valence state and proportion of its elements and content of oxygen vacancy can be adjusted in a large range. Therefore, hexaaluminate catalysts with high catalytic activity can be designed by means of chemical tailoring according to the characteristics of chemical reactions and requirements for catalysts.

In this work, La-hexaaluminate is employed as the cathode material for co-electrolyzing H2O and CO2/air mixture to produce syngas. A series of characterization methods are used to evaluate the basic physical properties of hexaaluminate, including phase structure, oxygen vacancy concentration, thermal stability, thermal expansion coefficient and chemical compatibility with electrolyte materials. Moreover, the stability of electrolytic cell in various operating conditions was investigated, the morphology of cathode and anode materials before and after the operation of the electrolytic cell were compared. The reason of performance attenuation of the electrolytic cell was preliminarily analyzed. The new scheme developed in the present work, provides a way for the effective utilization of O2-containing low concentration CO2 captured by DAC, which is not only useful for alleviating the greenhouse effect, but also gains extra fuels with the help of renewable energy.

References:

1. J. Song, J. Liu, W. Zhao, Y. Chen, H. Xiao, X. Shi, Y. Liu, and X. Chen, Ind Eng Chem Res, 57, 4941 (2018).

2. Y. Song, X. Zhang, K. Xie, G. Wang, and X. Bao, Adv Mater (2019).

3. M. Tian, X. Wang, and T. Zhang, Catal Sci Technol, 6, 1984 (2016).
(Invited) High Temperature Steam/CO2 Co-electrolysis Using Solid Oxide Electrolyser Stack at Shanghai Institute of Applied Physics
Authors: Xiao Guoping , Guan Chengzhi , Chen Peng , Wang Jian-Qiang
Published: May 2020

The high temperature steam/CO2 co-electrolysis using solid oxide electrolyser cell technology is considered to be an important alternative for syngas production with carbon-free process. Previously, the co-electrolysis of steam and CO2 in single cell have been published in Faraday Discussions by our team, and electrolysis parameters have been investigated and optimized systematically. In this paper, we carried out the steam/CO2 coelectrolysis experiment using a 30-cell SOC stack composed of NiO-YSZ/YSZ/GDC/LSCF-GDC with the single cell effective area of 63cm2 (developed by Ningbo SOFCMAN Energy Technology Co., Ltd). The electrochemical performance of stack was investigated through OCV, I-V and long-term stability tests. From OCV and I-V curves, we can see the electrochemical performance of steam/CO2 co-electrolysis is slightly worse than that of steam electrolysis. And stability test was carried out in galvanostatic electrolysis mode (750 oC, 0.25 A/cm2, H2/H2O/CO2= 20/53.33/26.67(molar ratio); H2: 1.645NL/min) for 100hrs, the product of hydrogen electrode was analysis though rotameter and Agilent gas chromatograph 7820 , and the steam and CO2 utilization can be calculated to be 55.38% and 46.33%, respectively.

Figure 1
Composite Solid Oxide Cell Electrodes Based on Ruddlesden-Popper Nickelates and Co-Doped Ceria
Authors: Tsai Chen-Yu , Skinner Stephen J.
Published: May 2020

Significant interest has been directed towards the development of high performance air electrodes for solid oxide electrolysis cells, with a wide variety of potential materials considered. Much of the effort has been directed towards modification of conventional solid oxide fuel cell electrode materials, such as La1-xSrxCo1-yFeyO3-d (LSCF) and related perovskites with few studies directed toward new materials. The layered perovskites of the Ruddlesden-Popper (RP) family, Ln2NiO4+d where Ln = rare earth, have begun to receive some attention for this application, but the thermodynamic stability of these phases has precluded their widespread adoption. However the common degradation product of the Ln2NiO4 phases is the relatively high electronic conducting higher order RP materials such as Ln4Ni3O10-d. With the high electronic conductivity and stability in the SOC operating temperature window (600-900oC) these phases where Ln = La, Pr are promising candidates for solid oxide electrolyser application. However the uncertain ionic conductivity of these phases leads to consideration of composite materials exploiting an electrolytic material as the oxide ion conducting phase.

In this work we consider the Pr4Ni3O10-d (PNO) -Ce1-x-yPrxGdyO2-d (CGPO) composite phases evaluating the phase compatibility, percolation of the phases and electrode performance characterised using impedance spectroscopy. From evaluation of the impedance responses we find that the optimum performance of the composite electrode was obtained at an operating temperature of 710oC with a 50:50 wt% mixture. The area specific resistance of the electrode was determined to be 0.18 Ωcm2 at 710oC, with a minimum value of 0.08Ωcm2 at 784oC, Figure 1. Further, we evaluate the limiting processes of the cells, finding that at low electrolyte content the composite electrode performance is diffusion limited, whilst at higher electrolyte content the limiting process gradually changes to surface exchange. This work highlights the potential of this composite electrode and the considerable scope for device development based on these new materials.

Figure 1
Stability of Proton-Conducting Solid Oxide Electrolyzers for Hydrogen Production and Energy Storage
Authors: Hu Boxun , Marina Olga A. , Belko Seraphim , Reisert Michael , Aphale Ashish N , Hong Junsung , Ding Dong , Ding Hanping , Ma Zhiwen , Singh Prabhakar
Published: May 2020

Proton-conducting solid oxide electrolyzers (H-SOEs) provide promising opportunity to produce pure and dry hydrogen in steam electrolysis at relatively low operating temperatures (550-700˚C) utilizing electricity and heat generated from renewable energy sources. Compared to traditional high temperature (750-1000˚C) oxygen-conducting solid oxide electrolyzers (O-SOEs), lower operating temperature of H-SOE offers ease of thermal management, active stack and BOP materials cost reduction and reduction in chromium evaporation from metallic components. Like O-SOEs, preserving the long-term stability of H-SOEs is one of the technical challenges for large-scale hydrogen production. In this technical contribution, results of experimental evaluation of H-SOEs under real-world operating conditions are presented. As fabricated and posttest cells have been characterized using operando electrochemical impedance spectroscopy, X-ray diffraction, focused ion beam-transmission electron microscopy and other bulk and surface characterization techniques to examine bulk, surface and interface stability of electrochemically active components. Phase and morphological changes, compositional uniformity and interfacial reaction products formation have been examined. Electrolyte/electrode materials stability, cell and gas seal fabrication processes, and gaseous impurities affecting long-term electrochemical performance will be discussed. H-SOE electrochemical performance model based on cell materials and operating conditions has been proposed and validated based on single cell testing data.
(Invited) Carbon Dioxide as a Sustainable One-carbon Synthon
Authors: Manthiram Karthish
Published: May 2020

Carbon dioxide is an abundant and under-utilized feedstock in synthetic chemistry. At present, the most common one-carbon (C1) synthon is methane, which is converted to syngas via steam methane reforming under harsh conditions, for use in the synthesis of diverse chemicals, including acids, alcohols, and hydrocarbons. As an example, carbon monoxide can be used to conduct carbonylation reactions for extending carbon chains. An alternative C1 synthon involves direct use of carbon dioxide for carboxylation reactions in organic synthesis, circumventing the need to produce syngas as an intermediate and providing a carbon-negative route for chemical synthesis. Our group has shown sustainable routes whereby carbon-halogen and carbon-nitrogen bonds can be carboxylated and elucidated the mechanism by which this transformation occurs. These methods will be discussed in the context of the diverse scales at which decarbonization of the chemical industry needs to occur to secure a sustainable paradigm for producing critical chemicals and materials.
(Invited) Electrolyzer Development and Process Optimization: Paving the Road for Industrial Carbon-Dioxide Electroreduction
Authors: Endrodi Balazs , Kecsenovity Egon , Jones Richard , Janáky Csaba
Published: May 2020

Electrochemical reduction of CO2 is a promising method for converting a greenhouse gas into value-added products, utilizing renewable energy. Novel catalysts, electrode assemblies, and cell configurations are all necessary to achieve economically appealing performance. In this talk, I am going to present a zero gap electrolyzer cell, which converts gas phase CO2 to products without the need for any liquid catholyte. This is the first report of a CO2 electrolyzer cell, where multiple stacks are connected, thus scaling up the electrolysis process. The operation of the cell was validated using both silver nanoparticle and copper nanocube catalysts, and the first was employed for the optimization of the electrolysis conditions. Upon this, CO formation with partial current densities above 250 mA cm−2 were achieved routinely, which was further increased to 300 mA cm−2 (with ~95 % Faradaic efficiency) by pressurizing the CO2 inlet. Evenly distributing the CO2 gas among the stacks (parallel connection), the operation of the multi-stack cell was identical to the sum of multiple single-stack cells. When passing the CO2 gas through the stacks one after the other (serial gas connection), the CO2 conversion efficiency was increased remarkably. Importantly, the presented electrolyzer simultaneously provides high partial current density, low cell voltage (−3.0 V), high conversion efficiency (up to 40 %), and high selectivity for CO production; while operating at up to 10 bar differential pressure.

In the second part of the talk I will show how the cell can operate with pure water feed on the anode side, therefore avoiding the use of alkaline anolyte. A carefully designed activation protocol will be presented, which allows the cell to operate at high current density, using pure water feed. The effect of temperature and flow rate on the operation will also be presented. Finally, the nature of ion-transport through the anion exchange membrane as a function of the operational conditions will be discussed.
Developing Electrocatalysts for Ammonia Production
Authors: Liu T. Leo
Published: May 2020

Thermal production of ammonia (NH3) consumes a large amount of fossil fuels and is not sustainable. When coupled to the storage of renewable energy (e.g. solar and wind), electrocatalytic reduction represents a highly sustainable approach to convert N2 to valuable, energy rich NH3. In this presentation, we will present results on exploiting well-defined molecular electrocatalysts and heterogeneous electrocatalysts based on abundant base elements to address the electrocatalytic reduction of N2. Particularly, we will discuss on how to effectively and reliably evaluate electrochemical and spectroscopic data for the reduction of N2, which has been misinterpreted in recent literature.
Integrating Materials Design and Operando Spectroscopy for the Development of Next Generation CO2 Reduction and Biomass Valorization Catalytic Systems
Authors: Kornienko Nikolay
Published: May 2020

Electrochemical conversion of abundant feedstocks to fuels and value-added chemicals is rapidly gaining significance as a promising method to harness renewable electricity. Specific reactions within this context that my research group is focused on are the reduction of CO2 and oxidation of waste biomass. Because the design of new catalytic systems is inherently linked to a precise understanding of how these reactions proceed on heterogeneous surfaces, we put considerable efforts in developing methodology for opernado probing with Raman spectroscopy CO2 reduction and biomass valorization. This talk will detail our efforts in the design, electrochemical characterization, and spectroscopic investigation of

1) Composite systems of metallic nanoparticles decorated with functional organic ligands with steer CO2 reduction reactions down a select pathway on their surface

2) Tandem CO2 catalysis at the material-Metal Organic Framework (MOF) interface

3) Electrochemical oxidationof 5-hydroxymethylfurfural (HMF) on gold and transition metal oxide surface

In all, I show how using opernado Raman spectroscopy provides the mechanistic information on surface reaction mechanisms that enhance our understanding of functional hybrid interfaces and provides avenues for future materials design within the context of electrosynthesis of fuels and chemicals.

Figure 1
CO2 Reduction to Formate on Amine Modified Pb Electrodes
Authors: Zouaoui Nidhal , Ossonon Benjamin , Fan Mengyang , Mayilukila Dilungane , Garbarino Sebastien , Botton Gianluigi A. , Guay Daniel , Tavares Ana C
Published: May 2020

The electrochemical conversion of CO2 into high value-added chemicals and fuels using renewable energy sources is of considerable interest. Lead is among the best electrode materials for the reduction of CO2 to formic acid (or formate). However, the Faradic efficiency and energy efficiency of this process are hindered by the competing hydrogen evolution reaction (HER) at high reduction potentials. Strategies to improve the performance of Pb electrodes include the formation of metastable Pb oxide layers [1], the formation of 3D porous structures [2], and the growth of active Pb (100) surfaces on a dendrite-like secondary structure [3].

In this work, the growth of islands-like aryl-aliphatic, aminophenyl and nitrophenyl amines on Pb surfaces is proposed as an effective way to improve toward the Faradic efficiency of the reduction of CO2 to formate [4]. The aryl-aliphatic amines and aminophenyl porous layers were grafted on the surface of Pb surfaces using diazonium chemistry. The grafting of the amines results in a lower Pb electroactive sites which in turn hinders the HER but without blocking the active sites for the CO2 reduction, Figure 1.a. In fact, the porous organic film lowers the overpotential for the CO2 reduction reaction. Because of these combined effects, the Faradic efficiency for formate increases from 8% for the bare Pb to 94% for modified Pb electrodes, Figure 1.b. The present study offers a new route to decouple CO2 reduction from the HER, thus allowing the development of highly efficient and selective electrodes for the electroreduction of CO2 into value added products.

Figure 1. (a) Current densities recorded at -1.09 V vs RHE in Ar- and CO2- saturated electrolyte and their difference (Δ(CO2-Ar)) and normalized to Pb electrochemical surface area as a function of the extent of grafting (t) of Pb – modified electrodes with 4-ABA (4-aminomethylbenzene); (b) Faradic efficiency for formate as a function of the (N/Pb) atomic ratio determined by XPS for various Pb – modified electrodes: 4-ABA (4-aminomethylbenzene), 3-ABA (3-aminomethylbenzene), AEA (4-(2-aminoethyl)benzene), 4-NB (nitrobenzene).

Acknowledgments

This work was financially supported by NSERC (Canada). N. Z. acknowledges the Tunisian government for the INRS-Tunisia agreement scholarship. M.F. acknowledges the FRQNT (Quebec, Canada) for the PBEEE scholarship.

References

[1] C.H. Lee, M.W. Kanan, ACS Catalysis

2015,
5, 465-469.

[2] Z. He, J. Shen, Z. Ni, J. Tang, S. Song, J. Chen, L. Zhao, Catalysis Communications

2015
, 72, 38-42.

[3] M. Fan, S. Garbarino, G.A. Botton, A.C. Tavares, D. Guay, Journal of Materials Chemistry A

2017,
5, 20747-20756.

[4] N. Zouaoui, B. Ossonon, M. Fan, S. Garbarino, G. de Silveira, G. A. Botton, D. Guay, A. C. Tavares, Journal of Materials Chemistry A
2019
, 7, 11272-11281.

Figure 1
Water Oxidation By Amorphous Iridium Oxide: A Novel Synthesizing Method, Toward Industrial Applications
Authors: Najafpour Mohammad Mahdi , Salimi Payam
Published: May 2020

Water-splitting for hydrogen production has been recognized as a promising approach for storage sustainable energy. To make this technology economically competitive, it is critical to find an efficient and scalable synthesis method to develop a robust water-oxidizing catalyst (WOC), since the performance of electrolyzers is limited by water-oxidation reaction (WOR). Herein, an approach to synthesis highly active WOC with a one-step, low-cost, environmentally friendly, and accessible method by operating metallic iridium as the anode electrode in a two-electrode system and at a relatively high potential is presented. The obtained IrOx shows an overpotential of only 250 mV at 10 mA.cm-2 in 0.1 M HClO4 and remains stable under electrochemical conditions. Various characterization analyses are used to identify the structure and morphology of synthesized iridium oxide/iridium, indicates that the final product is a porous amorphous IrOx/Ir interface. The synthesis method can inspire a variety of opportunities to design and synthesize efficient metal oxide-based electrocatalysts for sustainable energy conversion and utilization.

Figure 1
Evaluation of Transition Metals with Lanthanoid Series Elements for Water Electrolysis
Authors: Swarnkar Priyanka
Published: May 2020

Enhancing the electrochemical activity of different electrocatalysts for environmental sustainability is of significant importance for the effective conversion of electricity and chemical energy. Enhancement of transition metal-based (Ni) electrocatalysts with lanthanide series elements has recently grown exponentially, and elements of rare earth (RE) (Ce) due to their unique characteristics are of special concern among different elements. In the present work a bifunctional catalyst (Ni-Ce) will be tested for Oxygen Evoluation Reaction (OER) and Hydrogen Evolution Reaction (HER). Cyclic voltammetry, as well as chronoamperometry, is used to test these electrocatalysts from alkaline to acidic medium for the OER and HER under laboratory conditions typically used for water electrolysis. HER and OER performance is tested in 1 M NaOH. The experimental results will suggest the factors affecting the hydrogen and oxygen evolution process and the catalyst will further be improved with the right combination of different group elements. sample characterization will be performed using XPS. Lower overpotential with Tafel slope will reflect the material activity for oxygen evolution reaction. Alteration in the morphology of the electrocatalyst is analyzed with scanning electron microscope
Highly Efficient PEM Water Electrolyser with Noble Metal Loading Less Than 0.2 Mg/cm2
Authors: Shi Yan , Min Xiangping , Lu Zhuoxin , Yan Changfeng
Published: May 2020

The high loading of noble metal is considered as one of the main barriers for cost-effective PEM water electrolyser. To reduce the loading of Iridium in anode, advanced OER catalyst and catalyst layer with enhanced activity, stability and lower noble metal loading must be developed. In this work, to improve utilization of Ir in anode, supported catalyst was prepared. W-doped TiO2 (W-TiO2) was developed as a conductive support for dispersing Ir active sites, then disordered IrOx nanoparticles with higher OER activity was loaded on the oxide support to form composite catalyst. With the benefits of high surface area of W-TiO2, the particle size of IrOx can be reduced to about 1nm and thus increase the number of active sites. Structure disordered IrOx nanoparticles can further enhance the OER activity due to the optimized oxidation state of Ir and large number of hydroxyl groups. The Ir mass activity of composite catalyst shows 7-8 times improvement than commercial IrO2, and stability maintains the same. The degradation mechanism of the obtained catalyst was also explored by identical location TEM (ILTEM), the dissolution of oxide support and detachment of Ir was considered as the main reason, besides no obviously passivation of support was observed. Finally, MEA with ultra-low noble metal loading was successfully prepared by conventional CCM method. The total noble metal loading of MEA can be reduced to 0.2mg/cm2 (Ir in anode: 0.11mg/cm2, Pt in cathode: 0.085mg/cm2), and water electrolyser still achieved 1.613V@1A/cm2 (75% LHV) and almost 400h stable operation under 1 A/cm2, suggesting good stability of supported catalyst and new MEA.

Figure 1
Surface Modified Layered Iron Vanadate As Bifunctional Electrocatalyst for Overall Water Splitting
Authors: Sari Fitri Nur Indah , Ting Jyh-Ming
Published: May 2020

Electrocatalysis water splitting is an attractive method to generate hydrogen from water. To date, the state-of-the-art catalysts to split water are based on noble metal, such as platinum for hydrogen evolution reaction (HER) and IrO2 and RuO2 for oxygen evolution reaction (OER). However, their scarcity and high cost limit the application. Therefore, great efforts have been devoted to explore highly active and cost effective catalyst materials. Recently, noble-metal free Fe-based catalysts have been demonstrated to be highly efficient for OER. It would then be a great advance if such Fe-based catalysts can become bifunctional for overall water splitting. In this work, surface modification of layered iron vanadate was performed to serve this purpose. The surface modification provides and protects additional electrochemical active sites during the reaction. Remarkably, the surface modified iron vanadate exhibits excellent activity for HER and OER, and hence great overall water splitting performance is demonstrated. This discovery not only provides a novel, low-cost, and efficient electocatalyst, but also expands the scope of non-precious metal elements for overall water splitting.

Keywords: layered iron vanadate, surface modification, HER, OER, water splitting.
(Invited) Protic Ionic Liquid Incorporated Polymer Membrane for Water Electrolysis
Authors: Ravikumar Ravikumar
Published: May 2020

Diethylmethylammonium trifluoromethanesulfonate [Dema][TfO] protic ionic liquid is used as an electrolyte for an intermediate temperature electrolyser for water decomposition at temperatures up to 100 oC. In this study we used a porous PTFE membrane impregnated with [Dema][TfO] as the electrolyte. The activation energy obtained from hydrogen pump test was 19.95 kJ/mol. Hydrogen evolution reaction (HER) and oxygen evolution reactions (OER) were studied in the solid-state cell equipped with an in-situ RHE reference electrode, using Pt/C cathode catalyst and IrO2 anode catalyst, respectively. The HER was observed at two different potentials, one at a peak potential of -0.47 V vs RHE with a limiting current density of -9.7 mA/cm2, assigned to reduction of hydronium ion. The second HER was observed at -0.63 V vs. RHE without a limiting current, assigned to the [Dema-H]+ cation reduction. Two oxidation peaks assigned to OER on IrO2 electrocatalyst was observed, one at 1.46 V and the second at 1.51 V vs RHE. The full cell water electrolyser achieved a current density of 100 mA/cm2 at 2.0 V with 60% RH feed at 100 oC. The stability of [Dema-H]+[TfO]- under electrolysis was studied with in-situ mass spectrometry which showed the loss of DEMA at potentials below -0.8 V vs RHE while [TfO]- anion was stable up to 2.5 V vs RHE.
Ionomer Content Optimization in Ni-Based Anodes for Alkaline Exchange Membrane Water Electrolysis
Authors: Baranova Elena A. , Cossar Emily , Barnett Alejandro Oyarce , Seland Frode
Published: May 2020

Anion exchange membrane water electrolysis (AEMWE) is an efficient and cost-effective solution to renewable energy storage due to its compact cell design and potential to operate using non-noble metal catalysts. [1] A known challenge to water electrolysis is the kinetically unfavourable oxygen evolution half-cell reaction (OER). Studies have shown that combining nickel (Ni) with small quantities of iron (Fe) can significantly enhances activity towards OER [2], and it has been shown that adding cerium oxide (CeO2), an oxygen conducting support, to catalyst materials can enhance catalytic processes. [3] AEMWE electrodes typically consist of a catalyst material, an ionomer and a solvent. For an efficient cell design, it is crucial to have an active catalyst, as well as the right amount of ionomer to properly stabilize and bind the catalytic layer, while still allowing for high hydroxide ion transport [4]. As such, this study covers the ionomer content optimization of NiFe-based nanoparticles (NPs) supported on CeO2 for anodes in AEMWE using a catalyst coated surface (CCS) electrode configuration. Preliminary AEMWE testing of the NiFe materials without ink optimization is covered in our previous work [5]. The materials tested were synthesized by chemical reduction in ethanol with sodium borohydride, and in-situ testing was done with a Fumatech membrane and ionomer. The ionomer content was tested on pure Ni NPs and the amounts tested were 7, 15, 25, 35 and 45 wt%. Scanning Electron Microscopy (SEM) of the resulting electrodes, Particle-size Distribution (PSD) of the catalyst inks, and in-situ testing showed that the best and most active catalytic layer was formed with 15 wt% ionomer. With the optimal ionomer content found, a more rigorous evaluation of AEMWE performance was carried out on NixFe(100-x) (x=90, 80 at%) both of which were also tested with 10 wt% CeO2. Polarization curves and electrochemical impedance spectroscopy results in 1 M and 0.1 M KOH are summarized and discussed. Additionally, catalyst stability of each of the materials was characterized by holding 0.5 A cm-2 for 12 hours, while measuring impedance every hour. Future work of this study will include long-term stability testing as well as testing the performance of different commercial and lab produced ionomer-membrane combinations with the Ni-based materials.

[1] M. Tahir, L. Pan, F. Idrees, X. Zhang, L. Wang, J. Zou and Z. L. Wang, Nano Energy
2017, 37, 136.

[2] M. Gong and H Dai, Nano Research
2015, 8, 23.

[3] H. A. E. Dole and E. A. Baranova, ChemCatChem
2016, 8, 1977.

[4] G. Li, D. Yang and P. A. Chuang, ACS Catal. 2018, 8, 11688.

[5] E. Cossar, A. O. Barnett, F. Seland, E. A. Baranova, Catalysts
2019, 9, 814.
Modeling Gas Diffusion Layers in Polymer Electrolyte Fuel Cells Using a Continuum-based Pore-network Formulation
Authors: García-Salaberri Pablo A. , Zenyuk Iryna V. , Gostick Jeff T. , Weber Adam Z.
Published: May 2020

A pore-network formulation is presented to model gas diffusion layers (GDLs) in polymer electrolyte fuel cells (PEFCs) using a continuum-based approach. The formulation can easily be integrated into macroscopic models in CFD codes, thus improving the modeling predictions while keeping a moderate computational cost.

The continuum-based pore-network formulation is based on a cubic lattice [1], which is divided into control volumes (cubes) of prescribed size. Pores and throats are placed inside the control volumes, and “connectors” of negligible volume interconnect the control volumes. The “connectors” are used to regulate the invasion-percolation pattern according to the size of the throat that links the pores within neighboring control volumes. Hence, the formulation can account for both invasion-percolation between pores as well as evaporation/condensation in the pore volume inside each control volume. This is a major advantage compared to traditional pore-network models based on a fully discrete formulation where phase-change phenomena are difficult to implement. Local anisotropic effective transport properties (permeability and diffusivity) are determined using a 1D resistor network analogy inside each control volume according to the size of the pore and throats in it.

The model is validated against capillary pressure curves and effective transport properties (effective diffusivity and permeability) measured ex situ. In addition, water saturation profiles are compared with distributions obtained using X-ray computed tomography [2].

[1] Jeff T. Gostick, Marios A. Ioannidis, Michael W. Fowler, Mark D. Pritzker, Pore network modeling of fibrous gas diffusion layers for polymer electrolyte membrane fuel cells, J. Power Sources 173 (2007) 277-290.

[2] P.A. García-Salaberri, G. Hwang, M. Vera, A.Z. Weber, J.T. Gostick, Effective diffusivity in partially-saturated carbon-fiber gas diffusion layers: Effect of through-plane saturation distribution, International Journal of Heat and Mass Transfer 86 (2015) 319–333.
(Invited) Electrocatalysis By Atomically Precise Metal Nanoclusters
Authors: Lee Dongil
Published: May 2020

The theoretically predicted volcano plot for hydrogen production shows the best catalyst as the one that ensures that the hydrogen binding step is thermodynamically neutral. However, the experimental realization of this concept has suffered from the inherent surface heterogeneity of solid catalysts. It is even more challenging for molecular catalysts because of their complex chemical environment. In this presentation, I report that the thermoneutral catalyst can be prepared by simple doping of a platinum atom into atomically precise gold nanoclusters such as Au25(SR)18 and Au38(SR)24, where SR is a thiolate ligand. The catalytic activity of the resulting bimetallic nanocluster for the hydrogen production is found to be significantly higher than reported catalysts. It is even better than the benchmarking platinum catalyst. The bimetallic metal nanoclusters represent a new class of catalysts that bridge homogeneous and heterogeneous catalysis and provide a platform for the discovery of finely tuned catalysts for hydrogen production from water. Studies of electrocatalysis by the bimetallic nanoclusters provide many important design principles for the development of electrocatalysts with tailored cluster structure and adsorption energy. These principles are illustrated with nanocluster-based electrocatalysts for water splitting and CO2 conversion.
(Invited) Water-Splitting Electrocatalysts Made By Pulsed-Laser in Liquids Synthesis
Authors: Müller Astrid M
Published: May 2020

Conversion of solar energy into storable fuels is urgently needed to combat climate change. Efficient, robust materials that are exclusively made of non-precious elements are imperative for tomorrow's global sustainable energy economy and necessitate the development of new nanostructured multi-metallic electrocatalysts that turn our most abundant feedstocks, water or carbon dioxide, into carbon-neutral fuels. The sheer number of possible elemental compositions in multi-metallic nanostructures requires a deep understanding of electrocatalytic mechanisms, including identification of reactive intermediates, to rationally design new materials and guide their optimization.

We used pulsed-laser in liquids synthesis to realize series of earth-abundant multi-metallic first-row transition metal oxide and hydroxide nanostructures. The pulsed-laser in liquids technique is a flexible synthetic strategy for surfactant-free nanomaterials with independently controlled compositional, morphological, and structural properties, and defect densities. It permits rapid preparation or modification of tailored, complex nanostructures in sufficiently large quantities to study them in bulk. Importantly, metastable materials become accessible as nanoparticles form from a laser-induced plasma that is confined by the liquid and characterized by very high temperatures and pressures, thus enabling access to extreme regions of the material's phase diagram.

Our approach enabled unprecedented atomistic-level structural and mechanistic insights into highly active and robust nickel–iron layered double hydroxide nanocatalysts for water oxidation in base; this understanding allowed rapid optimization. Operando spectroscopy data allowed us to identify a cis-dioxo iron(VI) reactive intermediate as the lowest-energy species before O–O bond formation during water oxidation electrocatalysis. Further, we capitalized on the unique advantages of the laser process for integration of our water-splitting electrocatalysts with photoanodes.
Photoelectrochemical Catalysis with Noble Metal Nanoparticles
Authors: Ross Michael B
Published: May 2020

Noble metal nanoparticles exhibit a variety of remarkable chemical and physical properties. They efficiently absorb visible and infrared light, can be synthetically manipulated to reveal complex surface morphologies, and are stable under harsh chemical conditions. These properties make them highly useful as renewable energy powered catalysts that take advantage of both photo- and electrical-excitation to drive chemical reactions. Au, Ag, Pt, Pd, and Rh nanoparticles have been used to carry out a variety of chemical transformations, including H2 generation, CO2 reduction, N2 reduction, and CH4 oxidation. This talk will describe recent efforts to understand the intersection of the various chemical and physical properties exhibited by noble metal nanoparticles, focusing on how they can be used and manipulated to drive small molecule renewable-powered catalysis.
Mechanistic Understanding of Material Transformations and Charge Transport at the Nanoscale in Solar Water Splitting Via Advanced Characterization Techniques
Authors: Toma Francesca Maria , Zeng Guosong , Eichhorn Johanna
Published: May 2020

Stable, cost effective, and efficient solar water splitting is the “Holy Grail” for sustainable clean fuels from two most abundant resources, sunlight and water. This approach requires the combination of light absorbers and surface coating to perform catalytic reactions and enhance the stability and charge transport. Thus, accurate characterization of the material transformations and charge transport mechanism is critical to enable design and development of new functional systems. In our approach, photoconductive atomic force microscopy and Kelvin probe measurements combined with photoelectrochemistry were developed to correlate morphological and functional heterogeneity in metal oxides. Furthermore, the pc-AFM combined with other spectroscopies, e.g., X-ray photoemission spectroscopy, X-ray absorption spectroscopy, and electron energy loss spectroscopy were carried out on nitrides materials to fundamentally understand stability during operating conditions.
(Keynote) Electrochemical Conversion of Sustainable Energy
Authors: Chorkendorff Ib
Published: May 2020

In this presentation, I will give an overview of some our recent progress in making nanoparticles in relation to electrochemical conversion of sustainable energy [1]. In the first case it will be used to elucidate size dependence and efficiency for catalysts related to the Water splitting i.e. Hydrogen- and in particular Oxygen-evolution reaction (OER) which is the limiting reaction and evaluate the scalability of scarce and expensive elements like the Pt-group metal under acidic conditions [2-4]. We shall discuss caveats of testing catalysts for water splitting [4] and investigate size dependence and isotope labelled experiments will be presented for NiFe nanoparticles for oxygen evolution under alkaline conditions [5]. Here we shall demonstrate a new principle for dynamic detection of gas evolution [6] allowing for a clear distinction between redox states and actual OER by simply measuring the amount of oxygen generated. This will be further pursued for OER catalysis on both Ir and Ru [7] and in the latter case down to 90 mV overpotential [8]. The change of Tafel slopes over many orders of magnitude in current density and mechanisms shall be discussed. If time allow we shall also discuss some of these catalysts used in connection with PEC [9].

References

[1] Z. W Seh, ..., I. Chorkendorff, J. K. Nørskov, T. F. Jaramillo, Science (2017) 355.

[2] E. Kemppainen, .. I. Chorkendorff, Energy & Environmental Science, 8 (2015) 2991.

[3] E. A. Paoli, F. ... I. E.L Stephens, I. Chorkendorff, Chem. Science, 6 (2015) 190.

[4] J Kibsgaard & I, Chorkendorff, Nature Energy, 4 (2019) 430.

[5] C. Roy, ... I. Chorkendorff; Nature Catalysis 1 (2018) 820.

[6] D. T. Bøndergaard, I Chorkendorff ...Electrochem. Acta 268 (2018) 520.

[7] R. R Rao, ...., I. Chorkendorff, I. E.L Stephens and Y. Shao-Horn,

Energy & Environmental Science 10 (2017) 2626.

[8] S. Scott, .... I. Chorkendorff. Submitted (2019).

[9] C. Moon,.... I. Chorkendorff. In preparation (2019).
Gas Diffusion Electrode Design for CO2 Electroreduction Beyond 1 a cm-2
Authors: Dinh Cao Thang
Published: May 2020

Electrochemical CO2 conversion to fuels and chemicals addresses the CO2 emission and renewable energy storage problems simultaneously. Existing infrastructure can be leveraged to take advantage of these fuels, and recycling CO2 results in a low- or zero-carbon fuel cycle. Converting CO2 into chemical feedstock enables the sequestration of CO2 into valuable products such as polymers.

Electrochemical CO2 conversion can be performed in aqueous- or gas-phase systems. Aqueous electrolysis, wherein the gaseous reactants are dissolved in the electrolyte, can achieve high selectivity. However, due to the low solubility of the gas reactants in the aqueous electrolyte and the long diffusion distance, current densities remain below few tens of mA/cm2—far from the >500 mA/cm2 regime needed to make ECC economically viable.

Gas-phase electrolysis of CO2 could overcome the diffusion limitation of the aqueous system, thereby enabling a much higher current density. In a gas-phase ECC system, a catalyst to reduce CO2 is deposited onto a porous hydrophobic substrate (gas diffusion layer) to form a gas diffusion electrode. The CO2 reaches the catalyst through the gas diffusion layer, reducing the required diffusion length and improving the mass transport. Current densities in the hundreds of mA/cm2 have been achieved using a gas-phase electrolysis system. However, other liquid-phase electrochemical technologies such as water electrolysis achieve multi Amperes/cm2. Also, critical challenges related to stability at high current densities remain.

Here, we present the gas diffusion electrode design that drives CO2 electroreduction to ethylene and ethanol at a current density > 100 mA/cm2 for > 100 hours. We then design the catalyst layer to achieve CO2 gas-phase electrolysis at current densities in the > 1 A/cm2 regime, and with the generation of multicarbon products. We report C2+ partial currents exceeding 1.3 A/cm2 at cathodic energy efficiencies above 40% – a sixfold increase relative to the best previously-reported comparable catalysts. These result in a full-cell energy efficiency towards C2 products of 20% above 1 A/cm2 operating currents.
Effective Conversion of CO2 to Ethanol over Sulphide Derived CuCd: The Importance of Cu2S/CdS Interfaces
Authors: Mosali Venkata Sai Sriram , Bond Alan M , Zhang Jie
Published: May 2020

Electrochemical CO2 reduction (eCO2RR) is the most sustainable method to covert atmospheric CO2 to industrial fuels. Various transition metals have been widely studied for eCO2RR. The selectivity of the products formed during eCO2RR mainly depends on the binding strengths of the metals those used as catalysts. While the metals that possess lower binding strengths for CO2 intermediates favour either CO or formate, those with very high binding strengths facilitate only HER.1 Among different eCO2RR active catalysts, Cu possess unique property of moderate binding strengths for eCO2RR intermediates due to which it can produce different reduced carbon products with poor product selectivity. Therefore, improving the selectivity of products over Cu surface is much desirable.2 More specifically attaining C2 hydrocarbons and alcohols, due to their higher energy density and that involve a complex 12 electron transfer process from CO2 to achieve them, is of scientific interest. For this, an approach by combining Cu with other eCO2RR catalysts is promising where the C1 product formed over the surface of transition metal is spilled over the adjacent copper surface and coupled with the eCO2RR intermediate attached to the copper.3 CdS is a semiconductor known to produce CO as major product during eCO2RR which makes it desirable to combine with copper. On the other hand, the weak conductivity of CdS can lower the reaction kinetics stabilising Cu+, which is known to favour the stabilisation of the intermediates of C2 products. In this study, we have developed sulphide derived CuCd catalysts with varying CuS/Cu2S – CdS grain boundary distribution patterns. On varying the ratio between Cu and Cd, we found the variation in grain boundary distribution. The presence of higher concentration of Cd (hCd – CuCdS) is observed to form high intact structure of CuS/Cu2S and CdS with significant Cu – Cd boundaries. This structure has facilitated an enhanced ethanol formation at a very lower potential of -0.8 V vs RHE with an exceptional faradaic efficiency of ~32% in CO2 saturated 0.1M KHCO3 solution. Based on XRD and TEM characterisation after bulk electrolysis, the role of cadmium sulphide as well as the grain boundary distribution in tuning the selectivity is elucidated.

References:

1. Ross, M. B.; De Luna, P.; Li, Y.; Dinh, C.-T.; Kim, D.; Yang, P.; Sargent, E. H., Nat. Catal,

2
, 648 (2019).

2. Nitopi, S.; Bertheussen, E.; Scott, S. B.; Liu, X.; Engstfeld, A. K.; Horch, S.; Seger, B.; Stephens, I. E. L.; Chan, K.; Hahn, C.; Nørskov, J. K.; Jaramillo, T. F.; Chorkendorff, I., Chem. Rev,

119
, 7610, (2019).

3. Ren, D.; Ang, B. S. H.; Yeo, B. S., ACS Catal.

6
, 8239 (2016).
(Invited) Cation Substitution in Metal Vanadates and Kesterites for Efficient Photoelectrochemical Water Splitting
Authors: Wong Lydia Helena
Published: May 2020

The efficiency of a photoelectrochemical water splitting system is strongly correlated with the efficiency of charge generation through light absorption and charge transport in the photoabsorber. A good photoabsorber needs to have both good optical and electronic properties, however most of the reported photoabsorbers do not show the optimized combination of these critical properties. In this talk, I will present our efforts in using cation substitution to design novel vanadates as the photoanode and kesterites as the photocathode of solar assisted photoelectrochemical system. In the case of vanadates, we found that partial substitution of Bi with Fe extends the bandgap from 2.6 eV (BiVO4) to 2.1 eV of FeVO4, and hence extending the theoretical STH% to around 16%. For kesterites, we demonstrated that substituting Cd and Ag into Cu2ZnSnS4 improve its charge transport properties, which leads to high photocurrent. Strategies to improve the charge transfer properties of these photoabsorbers by doping and passivation layers will also be presented.
(Invited) Photocatalytic Water Splitting: Particulate Model and Reactor Engineering
Authors: Hu Shu
Published: May 2020

Particulate photocatalysts offer a materials platform that potentially converts light energy to chemical energy at scale, water splitting being an immediate application. However, the state-of-the art solar-to-hydrogen conversion efficiency by particles is <5%, whereas photoelectrochemical cells have achieved 20%. In a holistic view, the conversion process for photocatalysts dispersed in a reactor involve coupled photophysical and electrocatalytic processes: light absorption, carrier generation, charge separation, charge transfer across the photocatalyst/co-catalyst/liquid interface, as well as mass transport of reactants and products. First, we extend the Gerischer/Lewis kinetic expression to semiconductor/liquid junctions that co-evolve hydrogen and oxygen. Because of the locally non-equilibrium environment, we carefully designed steady-state experiments to validate a mutually-dependent relationship of kinetics and energetics. On a single particle level, co-catalysts induce spatially-varying asymmetric energetics, i.e. band bending vs. flat bands; these asymmetric energetics drive electrons and holes to separate laterally along the liquid interface and accumulate at their respective sites; and it was found that redox selectivity defines local energetics thus influencing charge separation efficiency. Assembled by photocatalysts, a particulate panel or suspension produces hydrogen and oxygen which transport under pressure gradient. We will show the systematic measurement of product diffusion rates. Finally, we apply the multi-scale particulate model to implement a novel coating-stabilized water-splitting panel that is efficient and safe, delivering pressurized hydrogen under sunlight.
Charge Distribution Guided By Grain Crystallographic Orientations in Polycrystalline Battery Materials
Authors: Xu Zhengrui , Jiang Zhisen , Zhao Kejie , Liu Yijin , Lin Feng
Published: May 2020

Charge propagation and distribution determine the electronic, mechanical, and thermal properties of polycrystalline battery materials. There has been rapidly growing research interest to engineer the grain crystallographic orientation to modulate the charge distribution and chemomechanical properties for enhancing the cycle life, safety, and energy density of alkali metal ion batteries. However, establishing the relationship between charge distribution and grain crystallographic orientation remains a daunting challenge. In this work, we spatially measure the charge distribution in nickel-rich Li layered oxides as a function of the grain crystallographic orientation and establish a model to quantify the charge heterogeneity in the polycrystalline secondary particles. While the holistic “shrinking-core” charge propagation prevails in polycrystalline layered oxide particles, the orientation-guided charge propagation governs the charge distribution in local nanodomains. Compared to the randomly orientated grains, the radially aligned grains create less tortuous Li ion pathways, which improves the charge homogeneity as statistically quantified from over 20 million nanodomains, thus allowing for lower voltage hysteresis and higher capacity retention upon battery cycling. Our results suggest that tuning the grain crystallographic orientation may mitigate the stress buildup in secondary particles and increase the active particle utilization in practical batteries. The present study provides a fundamental guidance for managing the chemomechanical properties of polycrystalline battery materials through engineering the grain crystallographic properties.