 Electrochemical water splitting is a promising method for the production of hydrogen, H2, which is sustainable and pollution free. Green energy systems are being developed to reduce the external power consumption associated with H2 production. These include two electrode electrolysis of water, water splitting driven by photoelectrodes, solar cells, thermoelectric devices, triboelectric nanogenerators, pyroelectric devices, and electrochemical water gas shift devices. This review discusses recent advances in these green energy systems for efficient H2 production. This article was authored by Xiaoli, Lily Zhao, Jiayun Yu, and others.