Developing state-of-the-art water electrolysis technologies to advance large-scale hydrogen production is an effective way to ease the current energy crisis and environmental pollution. Conventional water electrolysis technology for hydrogen production primarily includes two half-reactions: anodic oxygen and cathodic hydrogen evolution reactions. Compared with the two-electron reaction process of the hydrogen evolution reaction, the oxygen evolution reaction involves a four-electron transfer, which has slow reaction kinetics, high overpotential, and low-added-value product of O2
and the generation of active oxygen species easily degrades the diaphragm, leading to the overall high energy consumption and low economic benefits, restricting its large-scale application. The development of highly efficient electrocatalysts for oxygen evolution reactions can considerably enhance hydrogen production efficiency for electrochemical water splitting. Although noble metal-based catalytic materials have high activity, they have poor stability and are expensive and scarce, preventing them from being extensively used. Efforts have been made to design cheap, high-activity, and robust stability nonprecious metal-based electrocatalysts to enhance the catalytic performance of the oxygen evolution reaction. Recently, several nonprecious metal catalysts with outstanding catalytic performance for the oxygen evolution reaction comparable with precious metal materials have been prepared; however, the existing water electrolysis technology for hydrogen production still faces some issues. It requires a high anode potential (>1.5 V vs
RHE) to drive the oxygen evolution reaction, and the O2
produced at the anode is not only of low value but also may crossmix with the H2
produced at the cathode, resulting in severe safety risks. Moreover, reactive oxygen species formed during the oxygen evolution reaction process can reduce the service life of ion-exchange membranes in electrolysis devices. These issues can be mildly addressed by designing and building anodic alternative reactions for the oxygen evolution reaction. For example, replacing the oxygen evolution reaction by the oxidation of hydrazine, urea, ammonia, alcohol, aldehydes, and other chemicals with a low energy barrier via
the reaction design can reduce the energy consumption of the water electrolysis process and produce high-value-added oxidation products, exhibiting crucial economic benefits. This review summarizes recent advances in the sacrificial agent oxidation and electrochemical synthesis reactions in replacing the oxygen evolution reaction and classifies these two types of replacement reactions. The corresponding oxidation mechanism, suitable nonnoble metal-based catalysts, and corresponding optimization strategies are discussed. In addition, possible challenges and future directions for the development of energy-saving hybrid water electrolysis systems driven by high-performance catalysts are outlined.