@article {1080, title = {Addressing the Stability Gap in Photoelectrochemistry: Molybdenum Disulfide Protective Catalysts for Tandem III{\textendash}V Unassisted Solar Water Splitting}, journal = {ACS Energy Letters}, year = {2020}, month = {07/2020}, pages = {2631-2640}, doi = {10.1021/acsenergylett.0c01132}, url = {https://doi.org/10.1021/acsenergylett.0c01132}, author = {Micha Ben-Naim and Reuben J. Britto and Chase W. Aldridge and Rachel Mow and Myles A. Steiner and Adam C. Nielander and Laurie A. King and Daniel J. Friedman and Todd G. Deutsch and James L. Young and Thomas F. Jaramillo} } @article {1087, title = {Highly efficient and durable III{\textendash}V semiconductor-catalyst photocathodes via a transparent protection layer}, journal = {Sustainable Energy Fuels}, volume = {4}, year = {2020}, pages = {1437-1442}, abstract = {

Durable performance and high efficiency in solar-driven water splitting are great challenges not yet co-achieved in photoelectrochemical (PEC) cells. Although photovoltaic cells made from III{\textendash}V semiconductors can achieve high optical{\textendash}electrical conversion efficiency, their functional integration with electrocatalysts and operational lifetime remain great challenges. Herein, an ultra-thin TiN layer was used as a diffusion barrier on a buried junction n+p-GaInP2 photocathode, to enable elevated temperatures for subsequent catalyst growth of Ni5P4 as nano-islands without damaging the GaInP2 junction. The resulting PEC half-cell showed negligible absorption loss, with saturated photocurrent density and H2 evolution equivalent to the benchmark photocathode decorated with PtRu catalysts. High corrosion-resistant Ni5P4/TiN layers showed undiminished photocathode operation over 120 h, exceeding previous benchmarks. Etching to remove electrodeposited copper, an introduced contaminant, restored full performance, demonstrating operational ruggedness. The TiN layer expands the synthesis conditions and protects against corrosion for stable operation of III{\textendash}V PEC devices, while the Ni5P4 catalyst replaces costly and scarce noble metal catalysts.

}, doi = {10.1039/C9SE01264H}, url = {http://dx.doi.org/10.1039/C9SE01264H}, author = {Shinjae Hwang and James L. Young and Rachel Mow and Anders B. Laursen and Mengjun Li and Hongbin Yang and Philip E. Batson and Martha Greenblatt and Myles A. Steiner and Daniel Friedman and Todd G. Deutsch and Eric Garfunkel and G. Charles Dismukes} } @article {1067, title = {Investigation of porous transport layer parameters for proton exchange membrane water electrolysis}, year = {2019}, abstract = {
  1. Presentation
  2. Investigation of porous transport layer parameters for proton exchange membrane water electrolysis
  3. Presenter
    Zhenye Kang
  4. Contributor
    Shaun M. Alia
  5. Contributor
    James L. Young
  6. Contributor
    Guido Bender
  7. LTE
  8. 2019
  9. Hilton Atlanta, Atlanta, GA, USA
  10. 236th ECS Meeting
  11. http://ma.ecsdl.org/content/MA2019-02/37/1747.short
  12. 11/6/2019, 10:47:45 AM
  13. 12/6/2019, 1:28:14 PM
Abstract
Published on October 17th, 2019 Hydrogen production through proton exchange membrane water electrolysis (PEMWE) is regarded as a very promising technology that offers a highly efficient and robust path to store electrical energy in form of hydrogen and further enables the integration of renewable energy into the electrical grid 1-3. The total cell voltage of a single PEM water electrolyzer cell is composed of the open circuit voltage, activation overpotential, diffusion overpotential, and ohmic loss overpotential 4. The total voltage of the cell can be expressed as Eq(1) 5. V=V_OCV+V_act+V_ohm+V_diff (1) Where V_OCV is the Nernst potential which is also called the reversible voltage and can be calculated from the Nernst equation or Gibbs free energy, V_act is the activation overpotential due to the electrochemical reaction and it represents the overpotential to drive the electron transfer and electrochemical reaction kinetics as described by the Butler-Volmer model, V_ohm is the ohmic overpotential caused by the resistances of the electronic/ionic components and interfacial contact resistances, and V_diff is the diffusion overpotential related to mass transport. Porous transport layers (PTLs) are key components in PEMWE. They facilitate mass transport, thermal and electrical conduction, and are required to sustain a good contact with adjacent components 6-8. It is expected that various PTLs with different structures and wettability exhibit nonidentical performance in PEMWE. In this study, a general model is established to investigate the PTL parameters of four inherently different PTLs, including non-treated Toray paper, PTFE treated Toray paper, sintered titanium particles and Ti felt. SEM images highlighting the structures of these PTL materials are shown in Figure 1. The materials, which differed in thickness, porosity, material and composition were evaluated with identical MEAs over a range of operating conditions for model validation. The resulting data indicate that the hydrophobic additives in the Toray paper will decrease the PEMWE performance due to increased mass transport loss and ohmic loss. Ti felt with similar thickness and porosity as non-treated Toray paper showed slightly reduced performance due to its higher ohmic loss. Sintered Ti particle PTLs exhibit much higher ohmic resistance than Ti felt and nontreated Toray paper, which may be attributed to its significantly larger thickness and/or an increased contact resistance. The experimental data was employed to validate the MATLAB/Simulink model which enables the simulation of the contribution of each overpotential. The model was used to successfully describe the effects of PTFE loading on PEMWE performance, as shown in Figure 2. The hydrophobic treatment resulted, as expected, in detrimental performance effects. The diffusion loss of a 20\% PTFE treated Toray paper is significantly higher than that of the nontreated PTLs (Figure 2). The modeling results also indicate that the change of the wettability of the PTLs by hydrophobic additives/agents, impacted not only the diffusion loss significantly, but also affected the ohmic loss and activation loss. This was specifically detrimental to PEMWE cell performance when operating at high current densities. The model that was validated in this study can be used to predict the effects of key PTL parameters and utilized to optimize PEMWE performance.
}, url = {http://ma.ecsdl.org/content/MA2019-02/37/1747.short}, author = {Zhenye Kang and Shaun M. Alia and James L. Young and Guido Bender} } @article {1069, title = {Performance enhancement of PEM electrolyzers through iridium-coated titanium porous transport layers}, journal = {Electrochemistry Communications}, volume = {97}, year = {2018}, month = {12/2018}, pages = {96-99}, abstract = {

Published on December 1st, 2018. Titanium-based porous transport layers (PTL) used in polymer electrolyte membrane (PEM) water electrolyzers suffer from surface passivation (titanium oxidation), which increases the interface resistance between the PTL and electrode. For long-term operation, PTLs are typically coated with considerable amounts of platinum or gold to ensure reasonable performance profiles over time. Moreover, it is well known that the oxide forms of platinum and gold are not stable under electrolysis conditions. In this study, an easy and scalable method is introduced to protect the titanium PTL from passivation by sputtering very thin layers of iridium onto commercially-available titanium PTLs. The iridium layer reduces the overall ohmic resistance of the PTL/catalyst layer interface and improves the cell{\textquoteright}s performance to that achieved with carbon-based PTLs. The coating process homogeneously deposited iridium throughout the inner structure of the PTL. The findings of this study may lead to the use of iridium as a protective layer for titanium PTLs, potentially enable operation at increased cell voltages and lead to increased electrolyzer durability.

}, issn = {1388-2481}, doi = {10.1016/j.elecom.2018.10.021}, url = {http://www.sciencedirect.com/science/article/pii/S1388248118302741}, author = {Chang Liu and Marcelo Carmo and Guido Bender and Andreas Everwand and Thomas Lickert and James L. Young and Tom Smolinka and Detlef Stolten and Werner Lehnert} }