bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Electrochemistry Meets Heterogeneous Catalysis for the Conversion of CO2 and N2 to Fuels and Chemicals
Authors: Holtappels Peter , Lapina Alberto , Hallinder Jonathan , Mogensen Mogens Bjerg , Chatzichristodoulou Christodoulos
Published: May 2020

Electrochemical reactors operating at intermediate temperatures (200 – 400 °C) can potentially have several advantages over their high temperature (600- 1000 °C) and low temperature (< 100 °C) counterparts. For example their potential of an increased catalytic activity enabling a decrease in material cost compared to low temperature cells, and can be thermally integrated into other chemical processes like synthesis of synthetic fuels and chemicals, such as methanol and ammonia.

Electrochemical reduction of CO2 to chemical building blocks such as CO, CH3OH, and CH4 is a dream for electrochemists, and high faradaic efficiencies have been reported for liquid electrochemical cells operated at ambient temperature, using e.g. Cu electrodes [1]. However, selectivity and electrochemical activity are far from being technically relevant, so that heterogeneous catalysis processes still are the matter of choice. Even more difficult is the electrochemical reduction of nitrogen f.i. to ammonia.

In this contribution, activities at DTU Energy are summarized using solid state electrochemical cells under operating conditions close to the well-known catalytic synthesis of methanol and ammonia. For CO2 reduction, cells based on CsH2PO4 as electrolyte and Cu based cathodes have been investigated towards their electrochemical activity in both H2/H2O and H2/H2O/CO2 containing atmospheres at elevated temperatures of 240 °C. Proton conducting ceramics cells based on barium cerate with Mo and Fe electrodes have been characterized in H2/N2 atmospheres between 300 and 500 °C. Electrochemical impedance analysis point towards a predominant hydrogen evolution and the role of adsorption and desorption processes as well as overpotential will be discussed.

[1] Y. Hori, Modern Aspects of Electrochemistry: Electrochemical CO2 Reduction on Metal Electrodes, Springer New York, USA 42 (2008), 89-189.
(Invited) Electrifying Our Fuel and Chemical Production
Authors: Chorkendorff Ib
Published: May 2020

Initially we shall discuss the need for electrifying fuels and chemical reducing the CO2 emmission of our society and give an example on how this can be done by supplying electrical heat instead of thermal heat for strongly endothermic reactions [1,2]. The same principles can also be used to convert sustainable energy into chemical energy by instead of making hydrogen sequentially adding protons from water splitting to CO or CO2 converting them into valuable fuels and chemical [4]. Fundamental aspect of electrochemistry on Copper shall be discussed [5-8] and it shall be shown that the CO2 balance is very important for scaling up the reaction in a fuel cell set-up [9]. I shall also touch upon electrochemical ammonia productions – facts or dreams [10].

References

[1] S.T. Wismann, ..... I. Chorkendorff, P.M. Mortensen, SCIENCE 364 (2019) 756

[2] S.T. Wismann, ..... I. Chorkendorff, Submitted (2019).

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

[4] S. A. Nitopi,..... I. Chorkendorff, Chem. Rev. 119 (2019) 7610.

[5] E. Bertheussen, ...I. Chorkendorff, Angewandte Chemie 55 (2016) 1450.

[6] S. B. Scott,.... I. Chorkendorff ACS Energy Lett. 4 (2019) 803.

[7] A. Tiwari,... I. Chorkendorff, and S. Horch, ACS Energy Letters (2019),

DOI:10.1021/acsenergylett.9b01064.

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

[9] M. Ming, .....I. Chorkendorff, and B. Seger, Submitted (2019).

[10] S. Z. Andersen, .... and I. Chorkendorff, Nature 570 (2019) 504.
Ammonia for Energy Storage and Power Generation: Review and Progress
Authors: Zhu Liangzhu , Cadigan Chris , Duan Chuancheng , O'Hayre Ryan , Sullivan Neal P
Published: May 2020

The use of ammonia as fuel or energy carrier has been attracting more attention over the past decade or so. Ammonia can be easily liquefied at room temperature at about 8 bar or at -33oC at ambient pressure, thus offering easy transportation or storage in liquid phase at room temperature while hydrogen is generally stored in gas phase at about 700 bar. Importantly, the infrastructure and distribution systems currently in place are far more compatible with ammonia than hydrogen. This unique property of ammonia makes it a promising alternative fuel for fuel-cell powered automobiles as well as in other stationary applications providing similar performance and stability may be achieved as compared with hydrogen fuel. While ammonia seems a very promising energy storage medium and carrier, it consumes about 3% to 5% of global natural gas and about 2% of the world's energy (1, 2). Over 1% of global CO2 emissions are attributed to ammonia synthesis, or on average about 3 tons of CO2 per ton of ammonia (3). Thanks to the fast development and commercialization of renewable energy technology, the above disastrous energy and environmental impacts related to ammonia production may be eliminated or mitigated by electrochemical ammonia production from renewable energy. However, attempts made so far on electrochemical ammonia production suffer from relatively low production rates which are far from being considered for commercialization. Degradation was also found to be pronounced in electrochemical ammonia production. In this talk, we will firstly give a review on both ammonia production and power generation using electrochemical cells, which will include cell performance and stability in both modes, ammonia production rate, conversion efficiency, type of proton source for ammonia production, electrode materials, catalyst, reactor design, etc. We will discuss reaction mechanisms, factors and challenges that are limiting further improvement of electrochemical ammonia production rates, the roles of hydrogen evolution reaction (HER) and nitrogen reduction reaction (NRR) on electrochemical ammonia production, and a few other related topics. We will also briefly cover the most recent progress at Colorado School of Mines on ammonia production and power generation in reversible protonic conducting electrochemical cells under U.S. Department of Energy's (DOE) Renewable Energy to Fuels through Utilization of Energy-dense Liquids (REFUEL) program. References 1. G. Qing, T. W. Hamann, Joule 3, 634-636 (2019). 2. R. F. Service, Science 361, 120 (2018). 3. G. Soloveichik, Nature Catalysis 2, 377-380 (2019).
Heterointerface Engineered Oxygen Electrode for High Performance Reversible Solid Oxide Fuel Cells (R-SOFCs)
Authors: Kim Jinhyeon , Lee Channyung , Choi Mansoo , Shin Hyunho
Published: May 2020

Solid oxide fuel cells (SOFCs) are promising alternatives to combustion technology for electric energy production due to no emission and high efficiency in chemical to electric energy conversion. Despite such advantages, the commercialization of SOFCs is hindered by the high operating temperature, resulting in a few problems, such as expensive system cost and short lifetime. Thus, while reduced-temperature SOFCs have been a long-lasting interest in the SOFC community, the sluggish oxygen reduction reaction (ORR) occurring at the oxygen electrode at intermediate temperature is the most critical challenge for the enhanced overall performance of SOFCs. As a promising strategy to achieve higher catalytic activity of oxygen electrode, the infiltration method has been employed due to not only extended active site for ORR by electrode surface decoration with active nanoparticle catalysts, but enriched oxygen vacancies additionally formed on the surface of infiltrates. Furthermore, heterointerface engineering in the infiltrated oxygen electrode has, more recently, emerged as a promising approach to optimize oxygen electrode performance. The lattice strain, induced by lattice parameter mismatch in heterostructured materials, can significantly influence the ORR/OER (oxygen evolution reaction) kinetics by changing oxygen defect formation energy and migration barrier.

We report the enhancement in the electrochemical performance of the La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) based heterostructured oxygen electrode, when infiltrated with aliovalent cation doped La2-xAxNi1-yByO4 (Ruddlesden-Popper, RP), leading to different intrinsic catalytic ability according to dopant; Sr and Co for A and B site, respectively, to generate oxygen defect (e.g., oxygen vacancy or interstitial O2-). This study demonstrates the impact of the oxygen defect in the infiltrates on the heterointerface, dominating ORR & OER kinetics in the heterostructured oxygen electrode, and investigate the primary oxygen defect for RP structured infiltrate to realize high ORR & OER activity.

To characterize the morphology of infiltrates anchored on the oxygen electrode surface and the heterointerface synthesized between infiltrated layers and backbones, scanning electron microscope (SEM) and transmission electron microscopy (TEM) are performed. The electrochemical performances of the infiltrated SOFCs were examined by electrochemical impedance spectroscopy and analyzed in terms of the distribution of relaxation time (DRT) from impedance data. Thermogravimetric analysis (TGA) and iodometric titration are conducted to understand the correlation between oxygen defect produced by aliovalent doping and electrochemical ORR activity.
(Invited) HT-PEM Fuel Cell Development for Product Definition and Scaleup
Authors: Primdahl Søren , Alfaro Silvia M. , García Héctor R. , Terkelsen Carina , Steenberg Thomas , Hjuler Hans Aage
Published: May 2020

“High Temperature” proton conducting electrolyte membrane (HT-PEM) fuel cells offer an attractive method of converting renewable energy carriers (e.g. methanol) to electricity, especially remotely and in transportation. A particular advantage is their ability to digest reformates containing a few % CO, thus not requiring high purity hydrogen.

Membranes of polybenzimidazole (PBI) allow for operation in the 150-200 °C range, as they do not require liquid-water for continuous moisturizing as do classical fluorinated polymer membranes. This temperature range is advantageous for the typically used Pt catalyst, as passivation by CO is limited.

A central challenge is cost reduction, with particular focus on Pt loading of electrodes. The critical trade-off is against lifetime and electrode performance while maintaining adequate tolerance to CO and fuel trace impurities. These limitations are sensitive to system and customer parameters via selection of fuel, reformer characteristics and operation mode.

Results will be presented and discussed on single cell lifetime in the 10.000 h range; objectives and results in electrode development and Pt loading, as well as results on methanol slip testing, start-stop testing and testing at elevated pressure. Lessons from early upscaling will be shared.
The Sabatier Electrolyzer: Harnessing Proton-Conducting Ceramics to Upgrade Carbon Dioxide into Methane
Authors: Pan Zehua , Sullivan Neal P
Published: May 2020

We present our development of the Sabatier Electrolyzer incorporating Sabatier catalysts into proton conducting ceramic membranes to synthesize CH4 and O2 from CO2 and H2O feed streams. Our work seeks to combine steam electrolysis and hydrogen production with carbon dioxide hydrogenation into a single Sabatier Electrolyzer reactor based on proton conducting ceramic membranes and Sabatier catalysts. Proton-conducting ceramic membranes transport reasonable rates of H+ ions at lower overall cell voltages at 400 - 500 ºC with low overpotentials for H2O splitting. The decreased electric power requirements for the Sabatier Electrolyzer are further enabled by autothermal operation; ohmic heating maintains the electrolysis cell at the necessary temperatures for high H+ conduction and effective Sabatier chemistry. Integration of the catalyst with the electrolyzer simplifies the system, improves reliability, and provides increased performance within a smaller package.

Figure 1 illustrates the Sabatier Electrolyzer concept. H2O and CO2 are fed to opposing electrodes of a protonic-ceramic electrolysis cell. Steam is electrolyzed with the product O2 exhausting from the cell. The product protons are driven across the protonic-ceramic membrane to the fuel electrode, where they react with CO2 to form CH4 and H2O. The combination of processes can match the exothermicity of CO2 hydrogenation with the endothermicity of H2O electrolysis, promoting thermal balance and high efficiency.

The Sabatier Electrolyzer cell features a BaCe0.4Zr0.4Y0.1Yb0.1O3-δ (BCZYYb4411) electrolyte, a Ni-BCZYYb4411 fuel electrode support, and a BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY) steam electrode. The Ni-cermet fuel electrode serves as the CO2-upgrading catalyst. To date, we have CO2 conversion and CH4 selectivity were demonstrated to be 28% and 43%, respectively, at 450 °C. This result is encouraging but still much lower than the thermodynamic predictions (~70% for CO2 conversion and ~95% for CH4 selectivity). In this presentation, we will review our efforts to achieve the thermodynamically predicted CO2 conversion and CH4 selectivity of 70% and 95%, respectively.

Figure 1
High-Performance Protonic Ceramic Electrochemical Cells for Hydrogen Production and Electricity Generation at Intermediate Temperatures
Authors: Ding Hanping , Tang Wei , Ding Dong
Published: May 2020

Achieving energy conversion between electricity power and hydrogen in protonic ceramic electrochemical cells (PCECs) is an emerging and attractive approach to store intermittent renewable energies which can be converted back to electricity in reversible operation. Economically competitive PCEC systems have distinct advantages over conventional oxygen-ion conducting counterpart (O-SOC), but further materials innovation is still needed to improve cell performance at reduced operating temperature (400~600○C), enhance system lifetime and reduce cost. To achieve efficient electrochemical hydrogen and power production with stable operation, highly robust and durable oxygen electrode is urgently desired to facilitate water oxidation and oxygen reduction reactions, which are the critical technical barriers for both electrolysis and fuel cell operation at reduced temperatures. The recent efforts in this study have been focused on developing new triple conducting electrode with perovskite or layered perovskite structure for high-performance and stable PCECs. The systematic material characterizations are carried out to evaluate the feasibility of activity, stability and interface compatibility, such as Fourier-transform infrared spectroscopy, high-temperature X-ray diffraction, hydrogen permeation and first-principal computation. The catalytic activity towards water splitting reaction is demonstrated in various electrochemical performance evaluation at 400~600○C. The long-term durability of the PCEC is examined to show the high resistance against transient current density change in reversible operation and high steam concentration.
Exploring High-Activity Copper Doping Zirconia Bi-Metal Oxides Catalysts for Methane Conversion at Room Temperature
Authors: Coco Cameron , Xu Nengneng , Zhang Yanxing , Clause Thomas , Schilling Austin , Wang Yu , Zhou Xiao-Dong , Qiao Jinli
Published: May 2020

Recently, a large quantity of research has been done on the conversion of CH4.(1) Compared to photo-catalysis and thermo-catalysis with precious metal catalysts and high reaction temperatures, the electro-catalysis path, which are always performed at room temperature, demonstrates more potential. In this regard, the electrochemical oxidation and conversion of CH4 to commodity chemicals, such as wide-application liquid alcohols, shows obvious economic benefit and high energy/ conversion-efficient. Zirconia (ZrO2) has rich Lewis acid active sites and huge electron acceptability, showing a remarkable adsorption capacity of CO32-.(2) Based on the above characters, zirconia-based hybrid has attracted a lot of attention and made some breakthroughs. In particular, transition metal oxide (TMO, such as NiO and Co3O4) doping ZrO2 forming TMO/ZrO2 compound demonstrates the potential of methane oxidation with CO32- at room temperature. Compared to NiO and Co3O4, copper-based (Cu) catalysts have a high activity and a long-term durability on forming liquid and gas organics of C1 catalysis reaction system (CO2 reduction reaction) at room temperature.(3-5) Hence, we present a facile strategy of using Cu ions doping ZrO2 to activate the hybrid activity by manipulating its crystal and electronic structure. As expected, the unique cylindrical ZrO2:CuOx catalyst shows remarkable CH4 oxidation performance with large current density differences (13.35 mA cm-2) and long-term electrochemical stability (negligible attenuation (10 %) after 48 hours). According to theoretical and experimental observations of the CH4 oxidation on ZrO2: CuOx hybrid, the high activity and durability of the hybrid should be attributed to 1) strong synergistic-coupling effect; 2) the unique doping structure forming favorable electronic and crystal structure; 3) fast oxidation reaction mechanism by shortening the reaction path. The mechanism could be described as that ZrO2 facilitating CO32- adsorption, then CO32- as the oxidizing agent source rapidly oxidizes CH4 adsorbed on the surface of Cu in zirconia.

Keywords: ZrO2:CuOx, Methane conversion, high activity, Unique doping structure

Uncategorized References

1. B. Wang, S. Albarracín-Suazo, Y. Pagán-Torres and E. Nikolla, Catal. Today, 285, 147 (2017).

2. M. Ma, B. J. Jin, P. Li, M. S. Jung, J. I. Kim, Y. Cho, S. Kim, J. H. Moon and J. H. Park, Advanced science, 4, 1700379 (2017).

3. H. Oguchi, H. Kanai, K. Utani, Y. Matsumura and S. Imamura, Applied Catalysis A: General, 293, 64 (2005).

4. Z. Riguang, L. Hongyan, L. Lixia, L. Zhong and W. Baojun, Applied Surface Science, 257, 4232 (2011).

5. S. Tada, K. Larmier, R. Büchel and C. Copéret, Catalysis Science & Technology, 8, 2056 (2018).
Manufacture and Electrochemical Test of Short Stacks Based on Protonic Ceramic Electrochemical Cell at Idaho National Laboratory
Authors: Gomez Joshua Yoel , Ding Hanping , Wu Wei , Zhou Meng , Ding Dong
Published: May 2020

As the technology of protonic ceramic electrochemical cells (PCEC) emerge for efficient hydrogen production as well as chemical electrosynthesis at reduced operating temperatures (400-600°C), the development of PCEC stack becomes critical to evaluate the feasibility of incorporating current PCEC material system into stacks. Idaho National Laboratory (INL) aims to develop stack manufacturing and electrochemical measurement capability for further enhancing system durability and reducing the overall cost. In this work, the large-scale 5cm×5cm and 10cm×10cm square cells are manufactured by high-temperature roll-to-roll method combining optimized additive manufacturing capability developed in INL. The integration of cells, sealants, current collectors, interconnects and gas manifolds involves significant exploration work of demonstrating high electrolysis performances. Both fuel cell and electrolysis operations are carried out to evaluate the effect of stack components on the performance with goal of achieving >70% performance of button cells. The long-term stability is operated at realistic conditions to assess the stack integration quality for further optimization of sealant materials, cell geometry, interconnect design and operating conditions. This early-stage work can benefit the technical and economic appraise on these new emerging technologies for industry attention and market penetration.
Observations of Mass Transport Losses in Two-Phase CO2 electroreduction
Authors: Krause Kevin , Lee ChungHyuk , Fahy Kieran F. , Lee Jason Keonhag , Shafaque Hisan Waleed , Bazylak Aimy
Published: May 2020

The need for capturing CO2 has become urgent with a record-breaking concentration of CO2 in our atmosphere (average of 407.4 ppm in 2018 [1]). CO2 electrolyzers are a promising technology capable of achieving a net-negative CO2 cycle when coupled with renewable energy sources. Aqueous electrolyte-based alkaline CO2 electrolyzers have recently been demonstrated to exhibit high selectivity for CO2 reduction to CO [2]. While the selectivity and enhanced performance of the aqueous alkaline environment are desired, the mass transport limitations introduced with this design have largely been overlooked.

In this study, we investigated the transport mechanisms near the electrolyte-catalyst interface over a range of current densities via sub-second in-operando X-ray synchrotron radiography. For the first time, we report fluctuations in cell overpotential driven by the dynamic accumulation and removal of gas at the electrolyte-catalyst interface region. Moreover, this fluctuation in potential due to the gas accumulation and removal in the liquid electrolyte layer was also observed to occur at a periodic rate that became increasingly frequent with increasing current density. The transient gas behavior observed from this study must be accounted for to further enhance the performance of alkaline CO2 electrolyzers with a liquid electrolyte.

References:

[1] Lindsey, R. “Climate Change: Atmospheric Carbon Dioxide”, NOAA Climate.gov, 2019.

[2] A. Martín, G. Larrazábal and J. Pérez-Ramírez, "Towards sustainable fuels and chemicals through the electrochemical reduction of CO2: lessons from water electrolysis", Green Chemistry, vol. 17, no. 12, pp. 5114-5130, 2015.
Manganese-Carbonyl Complexes As Catalysts for CO2 Electrochemical Reduction
Authors: Chardon Sylvie
Published: May 2020

Carbon dioxide conversion is increasingly gaining attention as CO2 is increasingly being regarded as a feedstock for the preparation of a wide range of value added commodities such as useful chemical raw materials or energy rich products. However, an efficient CO2 transformation process is challenging, but it has great potential for the demand of future resources that do not rely on petrochemical sources.

The CO2 reduction reaction requires high-yield, an input of energy and a catalyst. It can be performed on molecular catalysts. Among various experimental techniques that can be implemented, catalytic CO2 Electrochemical Reduction Reactions (CO2ERR) have promise as they convert electrical energy into chemicals (energy storage). In the past thirty years, several transition metal complexes, able to convert CO2 by CO2ERR, have been studied. This includes systems based on Re, Ru and Os bipyridyl carbonyl systems, however, very few earth abundant efficient metal based molecular catalysts have been reported so far.

Much of our present work[[1]] is focussed on developing and studying new Mn-based catalysts and understanding their catalytic properties towards CO2ERR pathway (Scheme), in order to gain a better understanding with the aim to improving and advancing this field of CO2 transformation.

Therefore here we will present our on-going research on Mn-carbonyl based molecular complexes, which is helping to better understand bipyridyl ligand effects on the CO2 catalytic electro(photo)reduction processes and especially the important role that ligands can have on catalytic activity and therefore efficiency and product selectivity, yield and overall catalyst stability under catalytic conditions.

References

[1] (a) M. Bourrez, F. Molton, S. Chardon-Noblat, A. Deronzier, Angew. Chem. Int. Ed. 50 (2011) 9903; (b) E. Torralba-Penalver, Y. Luo, J.-D. Compain, S. Chardon-Noblat, B. Fabre, ACS Catal. 5 (2015) 6138; (c) J.-D. Compain, M. Stanbury, M. Trejo and S. Chardon-Noblat, Eur. J. Inorg. Chem. (2015) 5757; (d) M. Stanbury, J.-D. Compain, M. Trejo, P. Smith, E. Gouré, S. Chardon-Noblat, Electrochim. Acta 240 (2017) 288; (e) M. Stanbury, J.-D. Compain, S. Chardon-Noblat, Coord. Chem. Rev. 361 (2018) 210. L. Le-Quang, M. Stanbury, S. Chardon-Noblat, J.-M. Mouesca, V. Maurel, J. Chauvin, Chem. Commun. 55 (2019) 13598.

Figure 1
Gold and Platinum Decorated Iron Oxides As Efficient Overall Water Splitting Catalysts
Authors: Sayeed Md Abu , O'Mullane Anthony
Published: May 2020

Transition metal oxides (TMOs) have gained much interest due their water splitting properties, producing oxygen and hydrogen as a clean source of energy, with the possibility of replacing fossil fuels for the future energy demands. Iron, Cobalt, Nickel and their oxides/oxyhydroxides have been investigated extensively due to their cost effectiveness and applicability in catalysing the water-splitting reaction, although there are some issues with performance degradation. In particular, recent studies on mixed metal oxides of Ni, Fe and Co show enhanced performance for oxygen and hydrogen production compared to the single metallic component.[1]

Iron oxides do not show good activity for the OER or the HER but are attractive for such an application if their activity can be enhanced given the low cost of such materials. Interestingly, it has been shown that fast active sites at FeOOH are responsible for enhanced OER activity within the mixed oxide system of Ni and Co.[2] A more recent development is the pursuit of bifunctional materials that can catalyse both the OER and HER which is attractive from a commercial viewpoint and electrolyser manufacturing. Again if Fe based materials can be used for this reaction, it would be highly beneficial.

In this work we galvanically replace iron and iron hydroxide nanostructures with Pt and Au and investigate the catalyst for both the OER and HER in an alkaline environment. The decoration of the iron surface with a low concentration of Pt or Au results in significantly increased activity for both the HER and more surprisingly the OER. The increased HER activity is expected as Pt is an excellent HER catalyst, however the presence of Au was also found to provide excellent performance. Although both Pt and Au are poor materials for the OER, they promote the reaction at iron oxide. To date, there have been no reports showing Au or Pt decorated Iron oxides that can split water effectively. The material was characterised using Scanning Electron Microscopy coupled with field emission spectra (SEM), Grazing Incidence X-ray Diffraction (GIXRD), X-ray Photoelectron Spectroscopy (XPS), and Transmission Electron Microscopy (TEM). The SAED and Dark Field Scanning Transmission Electron microscopy (DF-STEM) indicating that Au or Pt decorates the surface of the core polycrystalline nanocubes of iron. After the OER, a core-shell structure of Au-FeOOH or Pt-FeOOH is realised which is an effective bifunctional electrocatalyst that can catalyse both the OER and HER.

[1] aM. S. Burke, L. J. Enman, A. S. Batchellor, S. Zou, S. W. J. C. o. M. Boettcher, 2015, 27, 7549-7558; bM. Görlin, P. Chernev, J. Ferreira de Araújo, T. Reier, S. r. Dresp, B. Paul, R. Krähnert, H. Dau, P. Strasser, Journal of the American Chemical Society
2016, 138, 5603-5614.

[2] Z. Liang, H. S. Ahn, A. J. Bard, Journal of the American Chemical Society
2017, 139, 4854-4858.

Figure 1
NiFeMo Alloy Inverse-Opals on Ni Foam As Outstanding Catalysts for Alkaline Electrolytic Water Splitting
Authors: Hsieh Cheng-Ting , Huang Chun-Lung , Chen Yu-An , Lu Shih-Yuan
Published: May 2020

Hydrogen, a clean energy carrier with a high gravimetric energy density, is currently most economically produced with steam reforming of natural gases, in which fossil fuels are used as the raw material and CO2 is generated as a side product, both not environmentally sustainable. Renewable energy driven electrocatalytic water splitting is considered the most promising route for future hydrogen production. Its production cost, dominated by the electric energy consumption, however places it in a disadvantageous position, and highly efficient, cost-effective, and durable electrocatalysts, aiming to reduce the necessary working potential for cost competiveness, are critically important for the prevailing of the technology. The present work developed, based on the essential concept of improving quantity and quality of active sites of the catalyst, NiFeMo alloy inverse-opals on nickel foam as an extraordinary catalyst for alkaline electrolytic water splitting, achieving ultralow overpotentials of 33 and 249 mV for the hydrogen evolution reaction (HER) and 198 and 293 mV for the oxygen evolution reaction (OER) at current densities of 10 and 500 mA cm-2, respectively. Ultralow cell voltages of only 1.47 and 1.75 V are enough to deliver current densities of 10 and 500 mA cm-2, respectively, for overall water splitting, outperforming the benchmark couple, Pt/C and IrO2, and state-of-the-art electrolytic water splitting cells. The stability of the product is also outstanding, remaining stable after operations at an ultrahigh current density of 500 mA cm-2 for 50 hours. The success of the product catalyst is attributed to the much increased active site number with the construction of inverse-opals on nickel foam and the much enhanced intrinsic activities of the active sites through synergistic effects between the three constituent elements.
Novel Scalable Production of Single-Layer Graphene Coated-Metal Nanoparticles for Water Splitting
Authors: Shin Cheol-Hwan , Park Gisang , Zhang Chunfei , Yu Jong-Sung
Published: May 2020

Graphene-coated metal nanoparticles (NPs) have attracted great attention owing to their unique structural, photochemical and electrochemical properties based on electron communication between graphene and metal NPs. The development of highly efficient and non-precious metal-based electrocatalysts for water splitting comprising hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is still a big challenge. The hybridization of nitrogen (N)-doped carbon and cost-effective transition metals is a promising approach to produce highly active catalysts for HER and OER. Herein, a highly controllable chemical vapor deposition method is designed for large-scale synthesis of nickel nanoparticle wrapped by single-layer N-doped graphene (Ni@SNG), where silica work as molecule sieve to tactfully assist single-layer graphene growth by depressing diffusion of carbon radicals. The Ni@SNG sample synthesized at 800 oC shows excellent activity for HER in alkaline solution with a low overpotential of 100 mV at 10 mA cm-2, which is close to state-of-the-art Pt/C catalyst. Furthermore, the Ni@SNG catalyst supported on nickel foil is developed as a magnetic adsorption binder-free electrode, which exhibits much improved performance on catalytic activity and stability than common Nafion binder-based electrode. Therefore, magnetism adsorption technique, taking full advantages of magnetic catalysts, will be a greatly promising approach to overcome high electron resistance and poor adhesive stability of polymer binder-based electrodes in actual applications.

Figure 1
Mo Thio and Oxo-Thio Molecular Complexes As Water-Soluble Self-Healing Catalysts for Photocatalytic Hydrogen Evolution on 2D Materials
Authors: Taberna Pierre-Louis , Barbosa Juliana Barros , Chane Ching Jean-Yves , Balocchi Andrea , Marie Xavier , Gerber Iann
Published: May 2020

2D semiconducting nanosheets of Transition Metal Dichalcogenides are attractive materials for solar energy conversion because of their unique absorption properties. Recently, Hydrogen evolution reaction (HER) was achieved with thin 2D WSe2 nanosheets activated by well-known precious metal catalysts. Here, we propose for the first time, water-soluble, noble-metal-free, Mo thio- and oxo-thio-complexes anchored on 2D p-WSe2 nanosheets for efficient water splitting under visible light irradiation with photocurrent density up to 2.0 mA cm-2 at -0.2 V/NHE. These Mo thio and oxo-thio- molecular complexes represent an ideal class of catalysts, well-suited to functionalize 2D materials since they are stable in aqueous environments, cheap, environmentally benign to synthesize and process. We propose that the high performances of the oxo thio-Mo complexe catalysts arise from the strong adsorption on point defects of the 2D WSe2 substrate of Mo complexes such as (MoS4)2-, (MoOS3)2-, (Mo2S6O2)2- as shown from DFT calculations. More particularly, advantages of the water-soluble oxo-thio Mo complexes distributions, which spontaneously formed at well-defined pH are highlighted owing to their high electro-activity combined with their strong affinity toward point defects.
New Insights of the pH Effect on Hydrogen Evolution and Oxidation Reactions Mechanisms in Alkaline Solutions
Authors: Liu Ershuai , Mukerjee Sanjeev , Jia Qingying
Published: May 2020

The sluggish kinetics of the hydrogen evolution and oxidation reactions (HER/HOR) of Pt in alkaline solutions than in acid remains elusive. Elucidation of the mechanisms of the HER/HOR in alkaline can not only deepen our understandings of alkaline electrochemistry, but also help to rationalize the design of highly active catalysts for alkaline fuel cells and electrolyzers. Herein, we investigate the HER/HOR kinetics of a variety of catalysts including monometallic catalysts (Ni, Pt, Ru, Au) and bimetallic catalysts (NiMo, Pt-M) by comparing their HER/HOR performance in 0.1 M KOH and 1 M KOH. We found that the HER/HOR kinetics of these systems are not always slower in 1 M KOH (pH =14) than in 0.1 M KOH (pH = 13). These observations do not follow the general trend that the HER/HOR kinetics of a wide range of elements slows down with increasing pH1. We propose to resolve this inconsistency by pointing out that the pH is only one of the factors that affect the transport of the HER/HOR intermediates (hydroxyl for HER, Had for HOR) throughout the double layer region, among other factors such as the oxophicility of the surface sites, the cation environment, etc. These factors co-determine the HER/HOR kinetics of catalysts (such as Pt/C) that is limited by the transport of reactions throughout the double layer region. As the electrolyte changes from 0.1 M KOH to 1 M KOH, the pH shifts from 13 to 14, slowing down the HER/HOR kinetics. Meanwhile, the K+ concentration increases one order of magnitude, which promotes the transport of OHad according to the hard-soft acid-base (HSAB) mechanism we proposed recently2, thereby improving the HER but not the HOR until the K+ saturates. The change of the HER/HOR kinetics of a catalyst as the electrolyte changes from 0.1 M KOH to 1 M KOH is a counterbalance between these two effects, and thus varies case by case.

Acknowledgements.

This work was supported by the Department of Energy (DOE) under award number DE-EE0008082, Office of Naval Research (ONR) under award number N00014-18-1-2155 and the Graduate Thesis/Dissertation Grant of Northeastern University. This research used beamline 7-BM (QAS) and 8-ID (ISS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704.

References

(1) Herranz, J.; Durst, J.; Fabbri, E.; Patru, A.; Cheng, X.; Permyakova, A. A.; Schmidt, T. J. Interfacial Effects on the Catalysis of the Hydrogen Evolution, Oxygen Evolution and CO2-Reduction Reactions for (Co-)Electrolyzer Development. Nano Energy
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(Invited) Engineering Spinel Oxides to Boost Water Splitting Activity in Alkaline Electrolyte
Authors: Chu Deryn , Li Jiangtian
Published: May 2020

Seeking for non-precious electrocatalysts to replace platinum and ruthenium/iridium based noble materials for water splitting has been and will be a long-term research effort for sustainable and renewable energy supply. Multiple transition metal cations-based oxides like perovskite and spinel oxides are potential candidates thanks to their more flexibility in manipulating metal cations and acceptable electrical conductivity. Sluggish water dissociation kinetics, however, has been one of the rate-limiting steps in alkaline electrolyte. In this presentation, we will focus on engineering spinel oxides-based nanostructures to boost the water splitting activity for both hydrogen evolution reaction (OER) and oxygen evolution reaction (HER) in alkaline media. The contributions from tetrahedrally and octahedrally coordinated cations in spinel oxide with comprehensive electrochemical investigations will be discussed. Spinel oxides based nanoheterojunctions to the substantially improved activity for both HER and OER also will be highlighted in terms of promoting the water dissociation process and the intrinsic activity, and modulating the electronic configurations of cations.
Catalytic Growth of MWCNTs & Carbon Onions By Chemical Vapor Deposition on Nickel-Silica Nanocomposite Prepared Via Alcogel Electrolysis and Electrochemical Catalytic Study Towards OER
Authors: Ali Zulfiqar
Published: May 2020

Novel carbon nanostructures are desired for development of alternative to noble metal based electrocatalyst for sustainable energy technologies like production of hydrogen. In this work first nickel-silica nanocomposite with a particles size of about 20 nm has been formed by alcogel electrolysis and employed for catalytic growth of carbon nanostructures by CVD at 650-750°C using alcohol precursor diluted by argon followed by electrocatalytic study towards oxygen evolution reaction (OER) in 1M KOH solution has been carried. The carbon nanotubes of two different diameters, i.e. 10-30 nm and about 100-300 nm are seen at synthesis temperature of 650°C. The larger tubes are replaced by irregular structures and carbon onions at 750°C, with almost negligible nanotubes at the latter temperature. The diameter distribution of onion like carbon is found to be in the range 50-700nm. Shift from thicker nanotubes to onions may be partly attributable to higher diffusion rates of carbon that result in complete coverage of larger nanoparticles without allowing an open end to continue the growth of a nanotubes. Small radius of curvature and extra-ordinary distortion required for carbon onions has not allowed them to grow on small nanoparticles.

Key words: Nickel-silica Nanocomposite, Carbon Nanotubes (CNTs), Carbon onions, Chemical Vapor Deposition (CVD), OER
High Performance Sn@Pt/C and Sn@Pt/NG (C= Vulcan, NG= N-doped graphene) Core-Shell Nanostructures for the Hydrogen Evolution and Oxidation Reactions in Acid Media
Authors: Hernández-Vázquez G. , Dessources S. , Alonso-Lemus Ivonne Liliana , Escobar-Morales Beatriz , Rodríguez-Varela F.J.
Published: May 2020

In this work, the catalytic activity of nanostructured core-shell electrocatalysts synthesized by the polyol and bromide anion exchange (BAE) methods was evaluated for the Hydrogen Oxidation Reactions (HOR), and the Hydrogen Evolution Reaction (HER). The electrocatalysts were supported on Vulcan (C) and nitrogen-doped graphene (NG), and labeled as Sn@Pt/C-P, Sn@Pt/NG-P, Sn@Pt/C-B and Sn@Pt/NG-B. For comparison purposes, the monometallic electrocatalysts Pt/C-P, Pt/NG-P, Pt/C-B and Pt/NG-B were synthesized. The nominal metal:support ratio in all cases was 20:80 (wt. %), while the theoretical Pt:Sn atomic relationship at the core-shell nanostructures was 1:1. EDS analysis showed a C content of approximately 80 wt. %, although in general, the experimental metals concentration was not closed to the nominal one. XRD analysis indicated the crystalline structure of the electrocatalysts, with a crystallite size of less than 7 nm. TEM characterization confirmed the formation of core-shell nanostructures, with an average particle size of ~ 2.3 nm. The highest mass activity for the HOR was shown by the Sn@Pt/C-B electrocatalyst, while in terms of specific activity its performance similar to that of Sn@Pt/C-P. On the other hand, the evaluation of the HER indicated that the best electrocatalyst considering specific activity was Sn@Pt/NG-B, which also showed the highest mass activity (like that of Sn@Pt/NG-B at low overpotentials). The results of the evaluation of catalytic activity showed that the core-shell nanostructures have an enhanced performance for the two reactions, compared with the monometallic electrocatalysts. This indicated that they are good candidates to be applied in Polymer Electrolyte Membrane Fuel Cells (PEMFC) cells, as well as in PEM electrolyzers.
Synthesis of Binder Free NiFeOSe/Ni Foam Catalyst for Oxygen Evolution Reaction and Charge Storage Performance
Authors: Sahoo Malaya Kumar , Rao Ranga
Published: May 2020

Design of cost-effective electrocatalysts and supercapacitor electrode materials with enhanced functionalities has great potential in energy conversion and storage processes. Here direct growth of NiFeOSe on Ni foam is described and its catalytic performance for oxygen evolution reaction (OER) was evaluated. This novel noble-metal-free NiFeOSe/Ni foam catalyst was proposed as an excellent platform for water splitting to promote the oxygen evolution activity and stability. The advantages of this unique architecture are that the ultrathin and porous NiFeOSe nanowires can provide a huge number of exposed active sites, the highly-conductive Ni foam can promote the transfer of electrons, and the three dimensional-networked structures can facilitate the diffusion and penetration of electrolyte. Electrochemical measurements reveal that binder-free NiFeOSe/Ni foam electrode exhibits very low OER overpotentials of 244 mV at a high current density of 50 mA cm−2, small Tafel slope of 37 mV dec−1, and exceptional long-term stability of electrolysis for over 24 h in 1 M KOH alkaline medium. The binder free NiFeOSe/Ni foam electrode also exhibits a promising candidate for charge storage applications. This work

provides a promising strategy to develop transition metal based oxy-selenide as electrocatalysts for large-scale water-splitting and charge storage applications.
From NiRh2O4 to RhNi Alloy: Preparation and Characterization of Nanofibers for Hydrogen Evolution in pH-Universal Media
Authors: Jin Dasol , Yu Areum , Kim M. H. , Lee Youngmi , Lee Chongmok
Published: May 2020

Considering the growing attention to sustainable hydrogen production from water splitting, advanced materials for electrocatalytic water splitting are central to the area of renewable energy. Ideal water splitting catalysts should have not only low overpotential to produce hydrogen but also decent stability for a controlled period. While the previously reported water splitting catalysts have various compositions, the ones based on earth-abundant and non-precious metals are being studied extensively for hydrogen and oxygen production. However, noble metal oxides, in general, still exhibit superior electrocatalytic activity and enhanced stability under extreme environment compared with other cheap metals. Therefore, mixing non-precious transition metals (e.g. Ni, Co and Cu) with noble metals could be a possible strategy to utilize highly active but expensive noble metals providing economic feasibility.

Here we present the synthetic processes and physical/electrochemical characterization of single-phase NiRh2O4
nanofibers (NFs) and their reduced form, RhNi NFs. Those NFs are synthesized through electrospinning, a simple way to facilitate 1D nanostructure, and post-thermal annealing process with and without hydrogen atmosphere. Under a certain optimized condition, single-phase NiRh2O4
NFs and single-phase alloy RhNi NFs are synthesized without and with hydrogen atmosphere, respectively. To find the proper synthetic conditions, NFs are electrospun with varying the precursor mixing ratios and calcined at different temperatures. The morphology and compositions of NiRh2O4
NFs and RhNi NFs were characterized by a field emission scanning electron microscope (FESEM) equipped with an energy dispersive X-ray spectrometer (EDS), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The crystalline structure of the prepared NFs are investigated through high-resolution X-ray diffraction (XRD). Electrochemical activities of NiRh2O4
NFs and RhNi NFs for hydrogen evolution reaction (HER) are studied with rotating disk electrode (RDE) voltammetry in N2-saturated 1.0 M NaOH, 1.0 M PBS and 1.0 M HClO4 aqueous solutions; and compared with those of pure metallic Rh, Ni counterparts in addition to commercial Pt/C. This work was financially supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (NRF-2019R1F1A1059969 for CL) and Basic Science Research Program through the NRF funded by the Ministry of Education (NRF-2018R1A6A1A03025340 for YL and KMH).
Dynamic Self-Optimization of Hierarchical Porous Ni-Based Compounds As Bi-Functional, Efficient Catalysts for Water Splitting
Authors: Jiang Tao , Liu Taikai , Ansar Syed-asif , Montavon Ghislain , Liao Hanlin
Published: May 2020

Developing cost-effective, bi-functional electrocatalysts to efficiently convert intermittent typical renewable energy resources into hydrogen via water splitting is vital for realizing carbon-free energy cycle but remain challenges. Here, we report dynamically self-optimized (DSO) pre-electrocatalyst comprising NiAl framework covering defect-rich Ni crystallites for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in alkaline media. Core@shell Ni@NiO nanoparticles with lattice defects as the catalytically active phases are generated in situ on NiAl framework upon electrochemical DSO-HER, while Ni crystallites on NiAl framework in situ transform into wrinkled jamborite-(Ni(OH)2/NiOOH) hybrid nanosheets with severe lattice distortion that can mediate the OER efficiently upon electrochemical DSO-OER.

Under 1 M KOH aqueous electrolyte, the bi-functional DSO catalysts show an overpotential of 200 mV with Tafel slope 39 mV dec-1 and -33 mV with Tafel slope of 42 mV dec-1 for oxygen evolution reaction (OER) and HER at 10 mA cm-2. When assembled as the cathode and the anode in a single electrolyzer, the resulting Ni-based catalysts can give a superior overall water splitting output. Such a remarkable feature of the catalysts lies in the synergistic effect of the high intrinsic activity arising from the presence of complex lattice defects on the nanostructures of the active phases and the strikingly enhanced catalytic surface area together with the accelerated electron/ion transport associated with the hierarchical multi-porous architecture.

The material is seen to dynamically reform into different active interfacial species during DSO-HER and DSO-OER, where the pristine and activated catalysts are analyzed with XRD, SEM, Raman, XPS and TEM. The study shows that Ni-based compounds operate as effective bi-functional catalysts in alkaline water splitting, promising for integration into renewable technologies based electricity in alkaline water electrolyzers for sustainable production of hydrogen.