bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Engineering Challenges in Scaling-up Solar Water Splitting Devices
Authors: Abdi Fatwa 
Published: July 2022

The last decade has witnessed significant progress in the development of solar water splitting devices, with solar-to-hydrogen (STH) efficiency as high as 30% already demonstrated. However, two major challenges remain. First, the high-efficiencies (> 15%) have only been achieved using devices based on expensive and non-scalable III-V semiconductors. On the other hand, low-cost metal-oxide based devices, mainly using BiVO4 as the absorber, have only achieved STH efficiency of < 10%. Due to stability limitations, many of these metal-oxide based devices are operated in near-neutral pH electrolytes, which presents an additional mass transport challenge. Second, the majority of the demonstrated devices are still at the laboratory scale. Reports on large-area devices start to emerge, but they typically show much lower efficiencies. This is best illustrated in a recent review:[1] even when III-V semiconductor-based devices are considered, there is no report of devices with a semiconductor absorber area larger than 10 cm2 and STH efficiency > 10%.
In this talk, we will discuss the scale-up of our photoelectrochemical water splitting devices based on a complex metal oxide photoabsorber. Factors other than the semiconductor photoabsorber itself are found to be responsible for a total voltage loss of > 500 mV and therefore limit the overall performance of the large-area device.[2] To properly address this limitation, we quantify and break down the different loss mechanisms associated with the device scale-up and the practical operational conditions.[3] Concentration overpotential due to pH gradient is found to be a major contributor to the performance loss, and we show using multiphase multiphysics simulations and in-situ fluorescence measurements that careful control of natural and forced convection can overcome this limitation.[3-5] In addition, we also explore the possibility to achieve efficient product separation in devices with and without separators. The product crossover, optical and Ohmic losses are quantified using a combination of experiments and simulations, and the optimization of the device working parameters and/or separator properties to achieve the minimum overall loss will be discussed.[6,7]

References

J. H. Kim et al., Chem. Soc. Rev. 48, 2019, 1908

I. Y. Ahmet et al., Sust. Energy Fuels 3, 2019, 2366

F. F. Abdi et al. Sust. Energy Fuels 4, 2020, 2734

K. Obata et al. Energy Environ. Sci. 13, 2020, 5104

K. Obata & F. F. Abdi, Sust. Energy Fuels, 5, 2021, 3791

K. Obata et al. Cell Rep. Phys. Sci. 2, 2021, 100358

C. Özen et al. in revision
(Invited) Tailored Electrochemical Interfaces for the Production of Renewable Fuels
Authors: Escudero-Escribano Maria 
Published: July 2022

Tailoring the structure of the electrochemical interface at the atomic level is key to design new electrocatalysts for renewable energy conversion and storage. This talk will focus on novel catalyst materials and engineered interfaces for electrochemical energy conversion. In particular, I will discuss structure sensitivity and electrolyte effects for oxygen and carbon dioxide/carbon monoxide electrocatalysis.
First, I will present our work toward understanding the structure-activity-stability relations on high surface area nanostructured Ir-based materials for oxygen evolution. Then, I will highlight the importance of carrying out model studies on Cu-based surfaces to understand the structure-properties relations for CO2 and CO reduction. We have investigated the effect of pH, specific anion adsorption and potential dependence for CO reduction on Cu single-crystalline electrodes. We show how well defined studies are essential to design efficient electrocatalysts for the production of renewable fuels.
Tuning CO2 to CO Conversion on Metal-Doped Carbon Catalysts
Authors: Sarma Saurav Chandra , Barrio Jesus , Titirici Magda , Stephens Ifan Erfyl Lester 
Published: July 2022

One of the significant challenges faced during electrochemical CO2 reduction (ECO2RR) is the low selectivity of the products obtained. The best example is polycrystalline Cu, which can electrochemically produce hydrocarbons and alcohols but with poor selectivity.1, 2 To date, high selectivity has been achieved only towards CO and formate on Au and Sn surface, respectively but scalability and commercialization are limited owing to their cost and stability. Metal-nitrogen-carbon (MNC) materials are comparable to Au or Ag catalysts, albeit with their lower overpotentials, higher mass activity and high selectivity toward CO.3
,
4 During the pyrolysis of N-containing carbon molecules, different chemical functionalities such as pyridinic, pyrrolic and graphitic N atoms can be formed, each behaving as a product-specific active site. 5 It is still debatable whether pyrdinic or pyrrolic N is responsible for CO2RR activity; thus, it remains unclear how to favor CO2 reduction over hydrogen evolution.
In this work, we aimed to synthesize C2N-like covalent organic frameworks, with 8-10 Å pore size, tailored to host dual atoms coordinated to nitrogen. Such sites are expected to favor C-C coupling and produce multi-carbon products during ECO2RR. A step-by-step synthetic approach was employed to optimize the CO2RR:HER ratio through:

Tuning carbon:nitrogen ratio using two different synthetic approaches.

Reducing nitrogen in the carbon matrix through pyrolyzing at different temperatures (700, 800 and 900 oC),

Doping phosphorus and nitrogen into the carbon matrix

Tuning CO2RR product distribution through different metals (Fe and Ni) doping.

EXAFS and STEM studies revealed the presence of a mixture of single and dual atomic sites. XPS and ICP results showed that Fe and Ni loadings <2 wt% could be obtained in the C2N materials. Higher hydrogen evolution, owing to the higher N-content, was observed at a lower pyrolysis temperature which decreased at a pyrolysis temperature of 900 oC. Both Fe-NC and Ni-NC selectively produced CO, thus suppressing FE
H2 to <5%. Fe-NC also exhibited lower overpotential for CO production compared to its Ni-NC counterpart. A small percentage of ethanol and 2-propanol (FE<5%) was observed indicating the favoured C-C coupling on the dual-atomic sites. Further optimization of the metal-N coordination environment may allow for an improved selectivity for >C2 products.

References

K. P. Kuhl, E. R. Cave, D. N. Abram and T. F. Jaramillo, Energy Environ. Sci., 5, 7050 (2012).

S. Nitopi, E. Bertheussen, S. B. Scott, X. Liu, A. K. Engstfeld, S. Horch, B. Seger, I. E. L. Stephens, K. Chan, C. Hahn, J. K. Nørskov, T. F. Jaramillo and I. Chorkendorff, Chem. Rev., 119, 7610 (2019).

A. S. Varela, N. Ranjbar Sahraie, J. Steinberg, W. Ju, H.-S. Oh and P. Strasser, Angew. Chem. Int. Edit., 54, 10758 (2015).

A. S. Varela, W. Ju, A. Bagger, P. Franco, J. Rossmeisl and P. Strasser, ACS Catal., 9, 7270 (2019).

Y. Lum and J. W. Ager, Nat. Catal., 2, 86 (2019).
Modifying Crystal Symmetry and B-O Charge Distribution to Tailor Chemical Expansion in Mixed Conducting Perovskites
Authors: Anderson Lawrence O. , Yong Adrian Xiao Bin , Ertekin Elif , Perry Nicola H 
Published: July 2022

The exchange of ions between a lattice and the gaseous phase makes mixed conducting oxides ideal for a range of electrochemical applications. Altering oxygen ion concentration is accompanied by a change to electronic species concentrations, and this influences electrical, chemical, kinetic, and mechanical properties. The stability of electrochemical devices like fuel cells and batteries can heavily rely on the mechanical response to changes in chemical defect concentrations. Under both dynamic and steady-state operation of these devices, large volume strains and strain mismatch at interfaces can result in fracture, warping, and delamination that can cause performance degradation and/or failure. Strains between different materials are compared using the coefficient of chemical expansion (CCE), which normalizes the isothermal chemical strain by the change in defect concentration. Here, we advance the understanding of chemo-mechanical coupling through the study of PrGa0.9Mg0.1O3-δ and BaPr0.9Y0.1O3-δ by demonstrating CCEs 2-5x lower than any previously reported perovskite oxide1.
Isothermal CCEs were evaluated with in situ, high temperature, and variable atmosphere x-ray diffraction and dilatometry for chemical strains, and with thermogravimetric analysis for stoichiometry changes. The experimental results show chemical strains to be significantly lower than predictions from simple empirical models that assume pseudo-cubic structures and full charge localization on multivalent cations, like Pr. To evaluate actual charge distribution, in situ impedance spectroscopy and density functional theory calculations were performed. The collaboration of experimental and computational work combines accurate and reliable material characterization with insights into atomic and electronic structures that are difficult to probe experimentally.
Our results for the studied compositions indicate 2 primary factors that can be used to modify CCEs: 1) Altering the crystal structure away from the isotropic, cubic phase encourages anistropic expansion and lower CCEs in polycrystalline materials, and 2) Varying the distribution of charge along B-O bonds is shown to dramatically alter the CCE. While the first factor provides rather clear guidance to tailor expansion, we elaborate on the second by suggesting band structure design principles for near-zero redox-strain perovskites, and the benefit of locating holes partially or fully on oxygen is highlighted. These new findings add to the growing collection of crystal-chemical design rules for the rational tailoring of chemo-mechanical coupling in perovskite oxides.
(1) Anderson, L. O.; Yong, A. X. Bin; Ertekin, E.; Perry, N. H. Toward Zero-Strain Mixed Conductors: Anomalously Low Redox Coefficients of Chemical Expansion in Praseodymium-Oxide Perovskites. Chem. Mater.
2021, 33 (21), 8378–8393. https://doi.org/10.1021/ACS.CHEMMATER.1C02739.
Understanding Coupled Electro-Chemo-Mechanics during I
n Situ Li Metal Anode Formation in Anode-Free Solid-State Batteries
Authors: Kazyak Eric , Yadavalli Srinivas , Lee Kiwoong , Wang Michael , Sanchez Adrian J. , Thouless M.D. , Sakamoto Jeff , Dasgupta Neil P. 
Published: July 2022

Solid-state batteries (SSBs) are potentially disruptive for a range of applications owing to their promise of high energy density, improved safety, and long cycle life. Their ability to enable Li metal anodes is a major advantage for energy density, but Li presents challenges for manufacturing due to its reactivity and the difficulty of fabricating thin Li films and high-quality Li/Electrolyte interfaces. Recently, in situ anode formation has shown significant promise for overcoming these challenges. In this approach, the cells are assembled without an anode (“Anode-free”), and Li metal is plated out from the cathode after fabrication. This reduces the need for inert atmospheres and reduces cell complexity, potentially lowering cost.
As Li is plated out for the first time, mechanical stresses evolve at the Li/Electrolyte interface due to the volumetric changes in the electrodes. These stresses and the coupling between mechanics and electrochemistry play an important role in the resulting uniformity and quality of the in situ formed Li electrode. This work leverages 3D operandooptical video microscopy to observe morphology changes during in situ anode formation on one of the most promising solid electrolytes, Li7La3Zr2O12 (LLZO). These morphology changes are linked to the electrochemical signatures and the dynamic evolution of mechanical stresses at the Li/LLZO interface. A mechanistic framework is built to understand these factors, which is then used to provide guidance on what parameters control uniformity, and how systems can be designed to improve the resulting electrode properties. The role of stack pressure and the importance of stack pressure uniformity is highlighted. The impact of interfacial toughness, current collector properties, and cell geometry are discussed. Based on this understanding, the areal Li coverage is improved by more than 50%, providing insight for future works to enable in situ anode formation in a range of material systems and cell architectures.
(Invited, Digital Presentation) Transport Characterization in Nano and Micron-Sized Multi-Component and Multi-Functional Materials
Authors: Haussener Sophia 
Published: July 2022

Porous and heterogeneous materials are core components in energy conversion and storage devices such as batteries, fuel cells and electrolyzers, or photoelectrochemical fuel generators. The heterogeneity and structural complexity of: i) the multi-functional nature of the applications requiring the presence of various functional materials in close vicinity, ii) nano- and micron-scale structuring of the material required to overcome the bulk material transport limitations, and iii) cheap and simple synthesis methods resulting in stochastic and complex morphologies. Understanding of the multi-physical transport phenomena and optimization of the component for enhanced performance, requires an accurate modelling and prediction of the transport properties, which heavily rely on the complex nano to micron-scale morphology.
In this presentation, I will show how tomography-based direct numerical simulation scan be used for the accurate numerical characterization of the heterogeneous components’ transport properties. We will use X-ray micro-tomography for the characterization of the (thermal) transport in partially saturated gas diffusion layers/electrodes or in porous thermochemical reactors, and FIB-SEM nano-tomography for the multi-physical transport characterization of photoelectordes for water splitting and catalyst layers of CO2 reducing gas diffusion electrodes. I will show how we have built up a digital library of (photo)electrodes. Furthermore, I will show how machine learning approaches can be used to guide the design of optimized structures.
(Invited) A Macro-to-Nano Zoom through the Hierarchy of a Lithium Ion Battery
Authors: Liu Yijin 
Published: July 2022

Lithium-ion battery (LIB) is featured by structural and chemical complexities across a broad range of length scales and, ultimately, it is the hierarchy of the battery structure that determines its functionality. The study of the battery function, degradation, and failure mechanisms requires a thorough and systematic investigation from the structural, chemical, mechanical, and dynamic perspectives. X-ray-based characterization techniques are playing an important role in this research field.
In this talk, I will review my group’s research activities over the past few years [1-10] by presenting a macro-to-nano zoom through the hierarchy of a standard battery cell [2] using a suite of state-of-the-art X-ray techniques. Damage [6-7], deformation, compositional [9-10] and chemical [1, 4-5] heterogeneity at different length scales are visualized and are associated to different degradation phenomena and mechanisms. Our results highlight the importance of the battery cathode material’s mechanical properties [7-8], which evolve upon battery cycling and could significantly impact both the immediate and the long-term cell behaviours. Statistical analysis, numerical modelling [4], and machine learning [3, 5-6] approaches are key components integrated in our research efforts and will be touched upon in this presentation. I hope this presentation will ignite enthusiasm and ideas for future collaborations.
References:
(1) J. Zhang et al., Nat. Commun. 11 (2020) 6342.
(2) G. Zan et al., J. Mater. Chem. A (2021) DOI: 10.1039/D1TA02262H.
(3) Z. Jiang et al., Nat. Commun. 11 (2020) 2310.
(4) S. Li et al., Nat. Commun. 11 (2020) 4433.
(5) G. Qian et al., ACS Energy Lett. 6 (2021) 687–693.
(6) Y. Mao et al., Adv. Func. Mater. (2019) 1900247.
(7) S. Xia et al., Nano Energy 53 (2018) 753-762.
(8) C. Wei et al., Acc. Chem. Res. 51 (2018) 2484-2492.
(9) J.-N. Zhang et al., Nat. Energy 4 (2019) 594–603.
(10) F. Lin et al., Nat. Energy 1 (2016) 15004.
Enhancement of Stability of Bi2O3-Based Ionic Conductor Via Microstructural Tuning
Authors: Jeong Incheol , Jeong Seung Jin , Yun Byung-Hyun , Lee Jong-Won , Lee Chan-Woo , Jung WooChul , Lee Kang Taek 
Published: July 2022

Oxygen-ion conductors with superior performance have been sought in the fields of energy conversion and storage.[1] Bi2O3-based ionic conductors which exhibit the highest known oxygen-ion conductivity have got attention for the next-generation solid electrolytes.[2] However, at intermediate temperatures below ~ 600 °C, their conductivity degrades rapidly owing to the cubic-to-rhombohedral phase transformation. Here, we demonstrate that grain boundary engineering can preserve the superior ionic conductivity of stabilized Bi2O3. To investigate the microstructural effect on stability, epitaxial and nano-polycrystalline model films of Er0.25Bi0.75O1.5 were fabricated by pulsed laser deposition. Interestingly, the grain boundary-free epitaxial film significantly improved the stability of the cubic phase while severe degradation is observed in conductivity of its polycrystalline counterpart. First-principles calculations revealed that thermodynamic stability of the cubic phase with respect to the rhombohedral counterpart is reduced near grain boundaries. These findings suggest novel aspects into the development of highly durable superionic conductors via physical manipulation of microstructure.

References

[1] E. D. Wachsman, K. T. Lee, Science 2011, 334, 935.
[2] B.-H. Yun, K. J. Kim, D. W. Joh, M. S. Chae, J. J. Lee, D.-w. Kim, S. Kang, D. Choi, S.-T. Hong, K. T. Lee, Journal of Materials Chemistry A 2019, 7, 20558.
(Keynote) Understanding How Porous Transport Layer Properties and Electrode Structure Affect the OER Electrode in an Anion Exchange Membrane Electrolyzer
Authors: Ul Hassan Noor , Duanghathaipornsuk Surachet , Chen Mengjie , Kohl Paul , Mustain William Earl 
Published: July 2022

Water electrolysis to produce hydrogen is gaining significant attention due to a significant decrease in the cost of renewable energy sources such as solar, wind, and tidal etc. Among the existing water electrolysis technologies, anion exchange membrane water electrolysis has recently emerged due to its potential advantages over proton exchange membrane electrolysis and traditional alkaline electrolysis. Anion exchange membrane electrolyzers (AEMELs) can allow for the use of PGM-free electrocatalysts and low-cost component materials due to its less corrosive alkaline environment while also enabling electrochemical H2 compression.
In an operating AEMEL, the anode electrode – where the oxygen evolution reaction (OER) occurs – controls a majority of the cell’s behavior. Recent work has shown that the most statistically relevant variables controlling the cell behavior are the catalyst choice, electrode structure and the properties of the porous transport layer (PTL). While the catalyst has been widely studied in the literature, significantly less attention has been paid to the catalyst layer design and the role of the PTL in dictating performance. The PTL is one of the most important components in AEM electrolyzer as it facilitates (i) water transport from the pores of the PTL through catalyst layer to the membrane towards hydrogen evolution reaction (HER) electrode, (ii) electron transport from the grains of the PTL through the catalyst material to the reaction sites in the catalyst layer, (iii) hydroxide transport from membrane to the reaction sites in the catalyst layer, and (iv) oxygen bubble removal from the reaction sites in the catalyst layer to the pores of the PTL.
In this study, various PTLs with different properties (e.g. material, fabrication methods, features size and thickness) were used to support the catalyst layer in operating AEMELs. It was found that higher porosity facilitates multiphase (O2, H2O, OH-) transport, however, catalyst layer adhesion deceases, resulting in higher contact resistance increasing cell overpotentials. It was also found that nickel based PTLs perform relatively better than stainless steel. Moreover, fiber felts offer slightly lower overpotentials compared to sintered structures likely offering enhanced surface area for catalyst deposition and access to the active sites. Furthermore, an increase in thickness did not affect transient voltage response, though it had a negative effect on durability – likely due to low permeability, O2 blocking the pathways while increasing overall cell resistance. The experimental findings presented here would provide important insights for development of PTL materials and structures for efficient and low-cost water electrolysis.
Integrated Thermo-Electric Measurement of Electrospun Nanofiber for Polymer Electrolyte Fuel Cell
Authors: Wang Shangshang , Huang Jun , Zhang Xing , Zhang Jianbo 
Published: July 2022

Polymer electrolyte fuel cell (PEFC), as an efficient hydrogen energy conversion device, has been developed for decades. Catalyst layer (CL), where the oxygen reduction reaction occurs, predominantly determines the performance of PEFC. Since 1889, the mass activity of catalyst layer has been improved for more than three orders of magnitudes, thanks to the invention of PFSA ionomer and highly dispersed catalyst on nano-sized carbon support. In recent years, introducing order into CL is bringing the CL performance to a higher level. The CLs with state-of-the-art performance feature nanofiber structures. One type of is ionomer nanofibers deposited with Pt/C catalyst on the surface, and another type is composite nanofiber containing ionomer, Pt/C catalyst, and binding polymer. Their superior performance may come from the ordered mass transport network and the size effect of nanofiber conductivity. To further improve the CL performance, the structure-property-performance relationship of ionomer nanofibers or composite nanofibers needs to be clarified.
In this work, we designed a setup to measure the proton, electron and thermal conductivity as well as the performance of a single ionomer or composite nanofiber. We developed a self-bonding method to fix the nanofiber on the micro-electrode. For proton and electron conductivity measurement, four-probe method was adopted to eliminate the electrical contact resistance and interfacial effect. For thermal conductivity measurement, Raman assisted steady state method was used to directly measure the temperature profile along the nanofiber. So, the measurement error resulting from the thermal contact resistance between the sample and the temperature sensor/heat sink can be eliminated. For performance measurement, three-electrode system was adopted using the Ag/AgCl electrode as the reference electrode and the Zn/ZnCl2 electrode as the counter electrode. We prepared nanofibers with different size, polymer content, and cross-sectional component distribution by controlling the ink recipe and electrospinning parameters. The integrated thermo-electric measurement found that the proton and thermal conductivity of nanofiber are one order of magnitude higher than bulk properties and increases with decreasing fiber radius. This is attributed to the oriented ionic morphology along the nanofiber. Furthermore, a nanofiber model was developed to extract the catalytic activity and gas diffusion coefficient of nanofiber. These characterization and modelling work can provide guidance to the design and optimization of catalyst layer with electrospun ionomer or composite nanofibers.