Atomically thin MoSe2/graphene and WSe2/graphene nanosheets for the highly efficient oxygen reduction reaction

Abstract

As a conceptually new class of 2D materials, inorganic graphene analogue (IGA) ultrathin nanosheets perform an increasingly vital function in various electronic devices. However, the relatively low electrical conductivity of IGA ultrathin nanosheets severely hampers their application as electrode materials in devices. Through in situ synthesis, we report the combination of inorganic graphene and graphene into atomically thin nanosheets as efficient electrocatalysts for the oxygen reduction reaction (ORR). Benefitting from the advantages of both IGAs and reduced graphene oxide, the g–MoSe₂ and g–WSe₂ nanocomposites showed excellent ORR activity associated with a number of exchanged electrons close to four, which corresponded to the complete reduction of oxygen into water. In particular, the two electrocatalysts exhibited a positive onset potential of −0.02 V (close to that of Pt/C, 0.02 V) and a high kinetic current density (J_K) of 10.22 mA cm⁻² for g–MoSe₂ and 10.77 mA cm⁻² for g–WSe₂ at −0.20 V. Compared with commercial Pt/C, these catalysts possess outstanding long-term durability and fuel crossover resistance capacity in alkaline media. Therefore, nanocomposites of inorganic graphene and graphene can be developed into low-cost and efficient alternatives (to the noble metal Pt) to be used as cathodic electrodes in fuel cells.