Metal Oxides and Sulfides for Overall Water Splitting

Electrochemical overall water splitting is an attracting technique for the renewable energy storage in form of chemicals, specifically green hydrogen energy. Low-cost transition metal oxides (TMO) as direct catalysts and transition metal sulfides (TMS) as indirect catalysts have been widely studied as highly active catalysts comparable to noble metal-based catalysts in this process. Herein, preparation strategies and electrocatalytic performances of TMO- and TMS-based bifunctional electrocatalysts are mainly presented. The basic mechanisms of the reactions on the electrodes are provided systematically and comprehensively and those relating key evaluation parameters for the evaluating electrocatalytic performance are introduced at first. Then, the well-defined structure, controllable synthesis, and bifunctional electrocatalytic performance-enhancing strategies for the TMO- and TMS-based electrocatalysts are discussed in detail. Finally, the outlooks of the future preparation of bifunctional TMO- and TMS-based electrocatalysts with high activity and excellent durability are summarized. It is expected to provide valuable insights for designing and fabricating of bifunctional TMO- and TMS-based electrocatalysts with superior capability to promote their application in the production of hydrogen at a large-scale and further to guide the creation of other types of nanomaterial-based catalysts for energy storage and conversion.