Noble-Metal-Free Molybdenum Disulfide Cocatalyst for Photocatalytic Hydrogen Production. 
Photocatalytic water splitting using powered semiconductors as photocatalysts represents a promising strategy for clean, low-cost, and environmentally friendly production of H2 utilizing solar energy.  The loading of noble-metal cocatalysts on semiconductors can significantly enhance the solar-to-H2 conversion efficiency.  However, the high cost and scarcity of noble metals counter their extensive utilization.  Therefore, the use of alternative cocatalysts based on non-precious metal materials is pursued.  Nanosized MoS2 cocatalysts have attracted considerable attention in the last decade as a viable alternative to improve solar-to-H2 conversion efficiency because of its superb catalytic activity, excellent stability, low cost, availability, environmental friendliness, and chemical inertness.  In this perspective, the design, structures, synthesis, and application of MoS2 -based composite photocatalysts for solar H2 generation are summarized, compared, and discussed.  Finally, this Review concludes with a summary and remarks on some challenges and opportunities for the future development of MoS2 -based photocatalysts.