Cocatalyst Engineering with Robust Tunable Carbon‐Encapsulated Mo‐Rich Mo/Mo2C Heterostructure Nanoparticle for Efficient Photocatalytic Hydrogen Evolution

Cocatalyst engineering with non‐noble metal nanomaterials can play a vital role in low‐cost, sustainable, and large‐scale photocatalytic hydrogen production. This research adopts slow carburization and simultaneous hydrocarbon reduction to synthesize carbon‐encapsulated Mo/Mo2C heterostructure nanoparticles, namely Mo/Mo2C@C cocatalyst. Experimental and theoretical investigations indicate that the Mo/Mo2C@C cocatalysts have a nearly ideal hydrogen‐adsorption free energy (ΔGH*), which results in the accelerated HER kinetics. As such, the cocatalysts are immobilized onto organic polymer semiconductor g‐C3N4 and inorganic semiconductor CdS, resulting in Mo/Mo2C@C/g‐C3N4 and Mo/Mo2C@C/CdS catalysts, respectively. In photocatalytic hydrogen evolution application under visible light, the Mo/Mo2C@C with g‐C3N4 and CdS can form the Schottky junctions via appropriate band alignment, greatly suppressing the recombination of photoinduced electron‐hole pairs. The surface carbon layer as the conducting scaffolds and Mo metal facilitates electron transfer and electron‐hole separation, favoring structural stability and offering more reaction sites and interfaces as electron mediators. As a result, these catalysts exhibit high H2 production rates of 2.7 mmol h−1 g−1 in basic solution and 98.2 mmol h−1 g−1 in acidic solution, respectively, which is significantly higher than that of the bench‐mark Pt‐containing catalyst. The proposed cocatalyst engineering approach is promising in developing efficient non‐noble metal cocatalysts for rapid hydrogen production.