| Summary: | In thermochemical water splitting cycles using an oxide catalyst, the temperature required for the catalyst reduction process (1000 °C–2500 °C) is much higher than that required for the hydrogen generation process (800 °C–1500 °C). Accordingly, there is an issue of inefficiency because the energy required to generate hydrogen is higher than the generated hydrogen energy. In this study, we investigated a method to decrease the energy required for the reduction of an oxide catalyst through the combination of polyvinylpyrrolidone as a reducing agent and Xe flash irradiation. A three-dimensional (3D) microporous nickel oxide (NiOx) was used as the oxide catalyst to maximize the surface area of the reaction and, hence, the amount of hydrogen generated from water. During the repeated hydrogen generation cycles, the maximum rate of hydrogen generation (10.6 µmol min−1 g−1) and the total amount of hydrogen generated (642 µmol g−1) were stably maintained without the degradation of the 3D microporous NiOx catalyst structure. The reduction method proposed here is expected to provide insights to resolve the issue of the inefficiency of energy in the catalyst reduction process during the hydrogen generation and regeneration processes using an oxide catalyst.
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