Ultrathin carbon coated CoO nanosheet arrays as efficient electrocatalysts for the hydrogen evolution reaction

Designing and developing a cost-effective and highly stable hydrogen evolution reaction (HER) electrocatalyst under alkaline conditions is critical for sustainable energy conversion and storage. Cobalt-based oxides have been considered as ideal HER electrocatalysts and have been intensively studied; however, their catalytic activity is still unsatisfactory. The modulation of electrical conductivity, which limits the catalytic activity of the transition metal cobalt-based oxides, is an effective way to improve the electron transfer efficiency, mass transfer and kinetic process of the HER. Herein, an ultrathin carbon layer coated cobalt(ii) oxide nanosheet array grown in situ on carbon cloth was synthesized by a simple two-step method for efficient HER. The obtained interconnected C@CoO nanosheet array possesses lower overpotentials and smaller Tafel slopes than those of bare CoO and shows excellent stability in 20 h long-term stability tests. The ultrathin carbon coated structure provides CoO with enhanced electron transfer efficiency, increased number of active sites and strong structural stability. This work paves an interesting route for boosting the HER performance of oxide-based electrocatalysts through introducing an ultrathin carbon coating for various energy systems in the future.