Hydrothermal synthesis of core-shell MoO₂/α-Mo₂C heterojunction as high performance electrocatalyst for hydrogen evolution reaction

Highlights: • A core-shell MoO₂/α-Mo₂C heterojunction was successful synthesized. • Such heterojunction exhibits a specific HER electrocatalytic activity. • The influence of the usage of β-cyclodextrin on the composition of molybdate compounds was demonstrated. - Abstract: Cost-effective electrocatalysts for hydrogen evolution reaction are attractive for energy conversion and storage processes. Herein, a variety of molybdenum-based catalysts have been synthesized by means of a simple hydrothermal method using cyclodextrin as structural guiding agent and carbon source. With optimizing the usage of cyclodextrin, both molybdenum oxidate and α-type molybdenum carbide can be controllable synthesized in terms of phase composition, morphology and porosity. X-ray diffraction patterns and high resolution transition electronic images show that the as-prepared sample appears a core-shell structure of MoO₂/α-Mo₂C heterojunction. Surprisingly, such heterojunction as an electrocatalyst exhibits a remarkable hydrogen evolution reaction (HER) performance with low overpotential of 100 mV in alkaline electrolyte, and of 152 mV in acidic condition at a current density 10 mA/cm², with very low Tafel slope of 50 mV/dec and 65 mV/dec, respectively. This specific activity of presented material is found to be superior to those of the most active Mo-based electrocatalysts reported so far. We believe that our finding of cost-effective electrocatalysts for hydrogen evolution reaction would open the door for future studies and applications of molybdenum compounds.