Hydration-Effect-Promoting Ni-Fe Oxyhydroxide Catalysts for Neutral Water Oxidation.

Abstract
Oxygen evolution reaction (OER) catalysts that function efficiently in pH-neutral electrolyte are of interest for biohybrid fuel and chemical production. The low concentration of reactant in neutral electrolyte mandates that OER catalysts provide both the water adsorption and dissociation steps. Here it is shown, using density functional theory simulations, that the addition of hydrated metal cations into a Ni-Fe framework contributes water adsorption functionality proximate to the active sites. Hydration-effect-promoting (HEP) metal cations such as Mg2+ and hydration-effect-limiting Ba2+ into Ni-Fe frameworks using a room-temperature sol-gel process are incorporated. The Ni-Fe-Mg catalysts exhibit an overpotential of 310 mV at 10 mA cm-2 in pH-neutral electrolytes and thus outperform iridium oxide (IrO2 ) electrocatalyst by a margin of 40 mV. The catalysts are stable over 900 h of continuous operation. Experimental studies and computational simulations reveal that HEP catalysts favor the molecular adsorption of water and its dissociation in pH-neutral electrolyte, indicating a strategy to enhance OER catalytic activity.

Citation
Wang, N., Cao, Z., Zheng, X., Zhang, B., Kozlov, S. M., Chen, P., … Sargent, E. H. (2020). Hydration-Effect-Promoting Ni–Fe Oxyhydroxide Catalysts for Neutral Water Oxidation. Advanced Materials, 1906806. doi:10.1002/adma.201906806

Acknowledgements
N.W., Z.C., and X.Z. contributed equally to this work. This work was supported by the Ontario Research Fund – Research Excellence Program, the Natural Sciences and Engineering Research Council of Canada, and the CIFAR Bio-Inspired Solar Energy program. N.W. and X.D.Z. acknowledge support from International Cooperation Projects of the Ministry of Science and Technology (2014DFE60170), National Natural Science Foundation of China (61474065), and (61674084), Tianjin Research Key Program of Science and Technology (18ZXJMTG00220), 111 Project (B16027), and Fundamental Research Funds for the Central Universities. B.Z. and H.S.P. acknowledge funding from Ministry of Science and Technology (2016YFA0203302), the National Natural Science Foundation of China (21875042), and the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning and Science and Technology Commission of Shanghai Municipality (18QA1400800). This work benefited from access to the 1W1B beamline at Beijing Synchrotron Radiation Facility. The TEM studies in this work were supported by Jingshan Luo. The simulations were performed using the KAUST supercomputer (HPC).

Publisher
Wiley

Journal
Advanced Materials

DOI
10.1002/adma.201906806

Additional Links
https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.201906806

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