Abstract
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.
Highlights
More than 90% of the hydrogen gas is produced through steam reforming from petroleum or natural gas, and the process suffers from the problem of carbon dioxide generation, which causes air pollution
Note that nickel oxide (NiOx) with a 3D microporous structure having a high surface area, which is capable of maximizing the amount of hydrogen generated by increasing the surface area of reaction with water, was used as a catalyst for hydrogen generation
The main purpose of this study is to develop a method for reproducing abundant oxygen vacancies in the oxygen-rich NiOx material after its use in the hydrogen generation step using PVP coating followed by Xe flash irradiation at a low temperature, in a short time
Summary
More than 90% of the hydrogen gas is produced through steam reforming from petroleum or natural gas, and the process suffers from the problem of carbon dioxide generation, which causes air pollution. The importance of the hydrogen production technologies based on water decomposition, which are environmentally friendly, is increasing. Since such processes of decomposing water to generate hydrogen require considerable energy, the role of the catalyst in achieving continuous water decomposition with low energy consumption is invaluable. Hydrogen generation using a thermochemical water decomposition method based on a metal oxide catalyst has been studied actively. Various studies have been reported on the thermochemical cycle method based on the combination of multi-step chemical reactions using a metal oxide and a nonmetal such as sulfur, chlorine, carbon, and iodine to decompose water at relatively low temperatures (below ∼1000 ○C) to generate hydrogen.. The hydrogen generation and regeneration process by the existing thermochemical cycle has a huge disadvantage: scitation.org/journal/adv more thermal energy (1000 ○C–2500 ○C) is consumed for the reduction step than the thermal energy (800 ○C–1500 ○C) required for the hydrogen generation step. in order to develop a real-time hydrogen energy system with high energy efficiency, it is necessary to develop a method that aids to decrease the required reduction energy and time
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