Boosting electrocatalytic water splitting by magnetic fields

Abstract

Overall water splitting efficiency is retarded by the kinetics of the sluggish oxygen evolution reaction (OER). Recently, increasing attention has been attracted to the spin-sensitive nature of the OER and the utility of magnetic fields (MF) for enhancing catalytic performance. Actually, MF should have performed even better, if we had a correct and comprehensive understanding of its possible effects on the whole OER system. Herein, we comprehensively discuss all possible effects of MF on the OER, including the magnetohydrodynamic effect in the electrolyte, the spin selectivity effect in the interface, and the spin alignment and magnetothermal effects in electrocatalysts. We point out that the MF type/setup and the magnetism of electrocatalysts are the two primary determinants for the real effectiveness of MF. This perspective is expected to provide instructive guidance for utilizing magnetic fields to improve the performance of water splitting as well as other spin-sensitive energy conversion reactions. Challenges and opportunities: • Renewable and clean energy sources are the basic foundation for the sustainable development of human society. Water electrolysis, with its ability to take advantage of rich water resources and renewable electric power sources, is one of the most promising technologies for hydrogen-fuel generation. • But its energy conversion efficiency is far beyond satisfactory despite of the tremendous efforts in the current knowledge framework. Most strategies to improve efficiency are associated with material engineering, which not only have the self-limitation in the actual performance improvement but also associate with tedious procedures. • Fortunately, external stimuli such as magnetic fields are expected to break through the limitations by providing an additional driven force at a low cost. In this regard, systematic discussion on its possible effects on the electrocatalytic water splitting system have practical significance for the development of green energy. Magnetic fields will perform more than ever thought on the efficiency improvements of various energy-conversion reactions. According to the physical basis, the effects of the magnetic field on water electrolysis are classified to the magnetohydrodynamic effect in the electrolyte, the spin-selective effect in the interface, and the spin alignment and magnetothermal effects in electrocatalysts. With a comprehensive understanding of the underlying mechanisms, it is hoped we could find effective solutions to the issues in the clean-energy fields.