Harvesting the two-electron process for solar water splitting

Solar water splitting represents one of the attractive approaches for the conversion of sustainable solar energy to produce hydrogen. Compared with the conventional four-electron process with stoichiometric production of hydrogen and oxygen, which need to be subsequently separated via an additional energy-consuming process, a two-electron process with simultaneous production of hydrogen and hydrogen peroxide as both value-added products is more appealing and offers a practical route toward water splitting with spontaneous product separation. Herein, two-electron solar water splitting is introduced from both thermodynamic and kinetic angles, along with an assessment of critical issues involved in the process. Moreover, technoeconomic analysis as well as research opportunities are presented with the aim to promote the development of this promising technology toward practical applications.