Research and perspectives on electrocatalytic water splitting and large current density oxygen evolution reaction

Abstract

With the consumption of fossil fuels and the deterioration of the ecological environment, the need for developing new, efficient, and sustainable sources of clean energy is urgent. The importance of “green hydrogen” in electrolytic water splitting has attracted worldwide attention not only from the scientific community but also from governments and industries. Hydrogen energy is considered an ideal alternative to fossil fuels because of its high energy density, environmental friendliness, and low pollution level. Hydrogen production from renewable energy sources using the electrolysis of water is the lowest carbon emission process of the many current hydrogen source options. The electrolytic water reaction is subdivided into two half-reactions, namely, the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. The HER is a relatively simple two-electron reaction. Compared to the HER at the cathode, the OER at the anode is a four-electron transfer process with slower kinetics and higher energy barriers. It is the decisive step in the electrolytic water reaction, receiving considerable attention from scholars. Recently, considerable developments in the research of high-performance electrolytic water catalysts have been reported as successful; however, the catalysts have been tested on a very small scale, usually under laboratory conditions, and can rarely operate continuously for hundreds of hours, far from meeting the needs of practical applications. Industrial-level electrocatalytic hydrogen production requires catalysts that are highly active, cost-effective, and stable at high current densities; thus, a great deal of work has explored efficient and highly durable active electrocatalysts to overcome the kinetic barriers that inhibit the reaction, particularly for the complex four-electron reaction of the OER. In summary, catalysts for oxygen precipitation reactions at high current densities will be the focus of future research. This paper reviews the current status of hydrogen energy development and various hydrogen production methods at home and abroad, focusing on an analysis of electrolytic water hydrogen production technology and proposing the requirements under large-scale industrial applications. Studying the OER mechanism has revealed that the activity of catalysts at high current densities can be enhanced by the following strategies: heteroatom doping, defect engineering, interface engineering, in situ self-growth, etc. Finally, the challenges in the field of high-current oxygen analysis at this stage of industrial development and the future direction of development are presented.

Keywords

• green hydrogen
• hydrogen production
• water electrolysis
• oxygen evolution reaction
• industrialization
• large current density