Boosting Electrocatalytic Hydrogen-Evolving Activity of Co/CoO Heterostructured Nanosheets via Coupling Photogenerated Carriers with Photothermy

Electrocatalytic hydrogen evolution from water splitting holds great promise for renewable energy conversion and usage, but its application is limited by high energy consumption. The development of a facile strategy to efficiently improve the efficiency of energy conversion and the sluggish reaction kinetics using low-cost and stable electrocatalysts is crucial but still highly challenging. Recently, light irradiation is demonstrated to be an efficient external driving force for improving the hydrogen evolution reaction (HER) activities of electrocatalysts. The enhancement of activities arise from either light-excited hot electrons/carriers or photothermy, while the integrating of two action mechanisms is rarely reported. Herein, we present a synergetic effect between light-excited carriers and photothermy to enhance electrocatalytic HER activities of a Co/CoO heterostructured ultrathin nanosheet array supported on Ni foam (denoted as Co/CoO-NF). After exposure to light irradiation, the overpotential at 10 mA cm^–2 decreased from 232 mV (dark) to 140 mV (light), and the Tafel slope decreased from 151 mV dec^–1 (dark) to 85 mV dec^–1 (light) for Co/CoO-NF. The coupling effect between photogenerated carriers and photothermy is demonstrated for the improvement of electrocatalytic activities through a series of characterizations, revealing a new avenue for developing a novel electrocatalytic system with high efficiency of energy conversion