Guanosine-assisted synthesis of a core–shell Mo2N/Mo2C/C structure for enhanced hydrogen evolution reaction

Abstract

Coupling molybdenum-based materials with carbon is an effective strategy to improve the hydrogen evolution reaction (HER) performance. However, achieving the desired surface-active sites by regulating the catalyst's morphology presents a challenge. Here, we present a novel approach using guanosine as an assisting agent to synthesize core–shell Mo₂N/Mo₂C/C composites. By utilizing guanosine in combination with ammonium heptamolybdate, we induce the formation of new hierarchical Mo-based structures through intrinsic self-regulating mechanisms. The presence of rich interactions between guanosine molecules, such as hydrogen bonding and π–π stacking, plays a pivotal role in achieving this successful outcome. Notably, a core–shell spherical MoO₂/CN polymer was formed when using an optimal amount of guanosine. By pyrolysis at 800 °C, this was transformed into the core–shell Mo₂N/Mo₂C/C composite. The unexpected core–shell structure was elucidated through ex situ XRD and SEM characterization, highlighting the dominance of carbon in the outer shells and molybdenum-rich phases in the core. The synthesized Mo₂N/Mo₂C/C composites exhibit a low overpotential of only 79 mV under alkaline conditions, which is comparable to that of commercially available Pt/C catalysts. Our study offers a promising route for developing noble-metal-free catalysts with enhanced HER performance, contributing to the advancement of green hydrogen generation technologies.