Journal
ACS ENERGY LETTERS
Volume 6, Issue 2, Pages 364-370Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsenergylett.0c02359
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Funding
- Technology Development Program to Solve Climate Changes [2018M1A2A2063861]
- Young Researcher Program through the National Research Foundation of Korea (NRF) - Ministry of Science, ICT [NRF-2019R1C1C1003435]
- GIST Research Institute(GRI) - GIST
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A new octahedral Co2+-rich Co oxide catalyst was reported to efficiently lower the cell voltage in anion exchange membrane water splitting for H-2 production. By increasing the amount of Co4+ at the active sites, the oxygen evolution reaction activity was enhanced, leading to a lower OER overpotential.
Here, we first report an octahedral Co2+-rich Co oxide with inactive Sb5+ ion as an oxygen evolution reaction (OER) electrocatalyst for efficient H-2 production by lowering the cell voltage in anion exchange membrane water splitting (AEMS). To enhance the OER activity of Co-based oxides, it is crucial to increase the amount of Co4+ at OER potential, known as the fast OER active site. Using in situ X-ray absorption spectroscopy, we observed most of the octahedral Co2+ in trirutile CoSb2O6 oxidized to Co3+ before the OER potential. Furthermore, oxygen vacancies facilitated further oxidation from Co3+ to Co4+ by tuning OH- adsorption energy of Co and then produced extensive active sites for O-O bond formation in OER compared to spinel-type Co3O4. As a result, we obtained a much lower OER overpotential of 360 mV at 100 mA/cm(2), providing 88% of the highest H-2 energy efficiency in the AEMS by applying a cell voltage of 1.7 V.
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