Novel cobalt quantum dot/graphene nanocomposites as highly efficient electrocatalysts for water splitting

Abstract

A cost-effective, non-noble metal based high-performance electrocatalyst for the oxygen evolution reaction (OER) is critical to energy conversion and storage processes. Here, we report on a facile and effective in situ strategy for the synthesis of an advanced nanocomposite material that is comprised of cobalt quantum dots (Co QDs, ∼3.2 nm), uniformly dispersed on reduced graphene oxide (rGO) as a highly efficient OER electrocatalyst platform. This nanocomposite electrocatalyst afforded a mass activity of 1250 A g⁻¹ at a low overpotential (η) of 0.37 V, a small Tafel slope of ∼37 mV dec⁻¹ and a turnover frequency (TOF) of 0.188 s⁻¹ in 0.1 M KOH, comparing favorably with state-of-the-art RuO₂, IrO₂ and Pt/C catalysts. The synergy between abundant catalytically active sites through the fine dispersion of Co QDs, and enhanced electron transfer generated from the graphene resulted in first-rate electrocatalytic properties toward the OER. These merits coupled with the higher stability of the nanocomposite hold great promise for triggering breakthroughs in electrocatalysis for water splitting.