Porous core-shell structured MoO₂-Mo₂C@C electrocatalysts for pH-universal hydrogen evolution reaction

Developing pH-universal and stable electrocatalysts for processes such as the hydrogen evolution reaction (HER) is challenging but necessary to achieve low-cost commercialization of hydrogen production. In this work, a facile and versatile method of carbon coating is developed to construct a MoO2, Mo2C and C core-shell heterostructure (MoO2-Mo2C@C). This heterostructure showed excellent HER performance in both acidic and alkaline solutions. The catalysts required overpotentials of 176 mV and 129 mV to reach a current density of 10 mA cm(-2) in acidic and alkaline solutions, respectively. Furthermore, the catalysts exhibited ultra-high structural stability over 200 hours of I-t tests. The results indicated that the porous carbon shell-coated heterojunction provides a MoO2-Mo2C heterostructure with high electrical conductivity, an increased number of active sites, and strong structural stability, thus boosting the HER performance. Theoretical calculations were also conducted to study the formation mechanism of the core-shell heterostructure, which indicated possible pathways for the transformation from MoO2 (011) to Mo2C (100).