Sustainable hydrogen production by molybdenum carbide-based efficient photocatalysts: From properties to mechanism.

Hydrogen is considered to be a promising energy carrier to solve the issue of energy crisis. Molybdenum carbide (MoxC) is the typical material, which has similar properties of Pt and thought to be an attractive alternative to noble metals for H2 evolution. The study of MoxC as alternative catalyst for H2 production is almost focused on electrocatalytic field, while the application of MoxC as a co-catalyst in photocatalytic H2 evolution has received in-depth research in recent years. Particularly, MoxC exhibits significant enhancement in the H2 production performance of semiconductors under visible light irradiation. However, a review discussing MoxC serving as a co-catalysts in the photocatalytic H2 evolution is still absent. Herein, the recent progress of MoxC on photocatalytic H2 evolution is reviewed. Firstly, the preparation methods including chemical vapor deposition, temperature programming, and organic-inorganic hybridization are detailly summarized. Then, the fundamental structure, electronic properties, and specific conductance of MoxC are illustrated to illuminate the advantages of MoxC as a co-catalyst for H2 evolution. Furthermore, the different heterojunctions formed between MoxC and other semiconductors for enhancing the photocatalytic performance are emphasized. Finally, perspectives regarding the current challenges and the future research directions on the improvement of catalytic performance of MoxC-based photocatalysts are also presented.