2022 Fiscal Year Annual Research Report
Understanding and development of highly efficient water splitting catalysts with core-shell structures for solar-hydrogen production
| Project/Area Number |
20K05684
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| Research Institution | Niigata University |
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Principal Investigator |
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | Water oxidation / Nickel salts / solar water splitting / Hydrogen production |
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| Outline of Annual Research Achievements |
We developed a nickel oxide electrocatalyst prepared from a nickel sulfate precursor (Sul-NiOx) that shows a highly efficient OER performance compared to that prepared from nickel nitrate (Nit-NiOx), nickel chloride (Chl-NiOx), or nickel acetate (Act-NiOx) precursors. The (Sul-NiOx) on a nickel foam (NF) substrate required an overpotential, η = 228 mV to generate a current density of 10 mA cm-2 with long term durability in alkaline KOH solutions, which is lower by 145 ~ 165 mV than those (η = 373 ~ 393 mV) for the Nit-NiOx, Chl-NOx, and Act-NOx catalysts. Moreover, the OER performance of Sul-NiOx compares advantageously with the most reported state of the art Ni-based electrocatalysts. Several investigations clearly show that the amorphousness and high valent Ni(III) of (Sul-NiOx), that can be easily converted to a nickel oxyhydroxide (NiOOH) active phase are responsible for its high OER performance. We also developed an efficient water splitting electrolyzer made of FeNiWOx/nickel foam (NF) anode and Pt / NF cathode to exhibit 240 mV of an overpotential for 10 mA cm-2, which is significantly lower than those (more than 315 mV) of previously-reported electrolyzers. We then constructed an efficient photovoltaic-electrolyzer (PVE) system of a double-junction GaInP/GaAs photovoltaic (PV) device connected with the present electrolyzer to demonstrate efficient and stable (for one month) solar water splitting with high solar-to-hydrogen efficiency (13.9 %) on one sun irradiation. The value is comparable with the top values (14.2 ~ 16%) in the state-of-art PVE systems.
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