Activating Edge-Mo of 2H-MoS₂ <i>via</i> Coordination with Pyridinic N–C for pH-Universal Hydrogen Evolution Electrocatalysis

It is highly desirable to develop all-pH-compatible hydrogen evolution reaction (HER) electrocatalysts that can be used universally in a variety of different electrolyzers and operated in different pH conditions, i.e., acid, alkaline, microbial, chlor-alkali, etc. So far, two-dimensional layered MoS2 and Mo-based carbon materials have been regarded as promising pH-universal HER electrocatalysts. 2H-MoS2 as a naturally occurring and thermodynamically favorable phase, yet still suffers from poor HER activity in neutral and alkaline electrolytes. Herein, a hybrid electrocatalyst, i.e., 2H-MoS2/N-doped mesoporous graphene, rich in interfacial Mo–pyridinic N coordination is fabricated. The optimized hybrid catalyst delivers long-term durability and outstanding HER activity with overpotentials of 110, 145, and 142 mV at 10 mA cm–2 in acidic, alkaline, and phosphate buffered solutions (PBS) media, respectively, outperforming most of the previously reported MoS2-based catalysts. Theoretical and experimental results demonstrate that the interfacial pyridinic N has a higher tendency to bond with Mo atoms than pyrrolic and graphitic N, and the edge-Mo coordinated with pyridinic N could serve as HER active sites. DFT calculations further reveal that Mo–pyridinic N coordination modifies the charge density of edge-Mo, in turn optimizing the hydrogen absorption energy and facilitating water dissociation, and thereby significantly promoting the intrinsic catalytic activity for the pH-universal HER process.