The synergistic effect of metallic molybdenum dioxide nanoparticle decorated graphene as an active electrocatalyst for an enhanced hydrogen evolution reaction

Abstract

As a durable and renewable fuel, hydrogen has attracted a huge amount of global interest in its production via different routes. Among these methods, the electrocatalytic hydrogen evolution reaction (HER) is one of the most promising ways for low-cost hydrogen production in the future. In this work, a simple redox hydrothermal method has been developed to fabricate a noble-metal-free MoO₂/rGO composite for a highly efficient HER. GO nanosheets provide oxygen-containing functional groups for precursor attachment, and restrict growth of MoO₂ nanoparticles (NPs) with a small size due to the space confinement effect among GO layers as well. Benefitting from a synergistic effect between metallic MoO₂ NPs and graphene, the obtained MoO₂/rGO composite exhibits excellent HER activity with a small onset overpotential of 190 mV, a large cathodic current density, and a small Tafel slope of 49 mV per decade, while MoO₂ NPs or rGO itself is not a very efficient HER catalyst. Additionally, the MoO₂/rGO composite displays good stability after 1000 potential cycles under both acidic and alkaline conditions. Dramatically improved HER activity and excellent stability are attributed to small size, more active sites, high conductivity and a synergistic effect of MoO₂ NPs and graphene. The development of the MoO₂/rGO composite as an enhanced active HER catalyst broadens the members of Mo-based HER catalysts and provides an insight into the design and synthesis of other noble-metal-free materials for the cost-effective and environmentally friendly catalyst in electrochemical hydrogen production.