Efficient electrocatalysts with strong core-shell interaction for water splitting: The modulation of selectivity and activity

Abstract

Optimum of electrocatalysts plays a key role in the design and development of cost-effective and environmentally benign technologies for energy conversion and storage. In this work, we study two kinds of core-shell structured electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in acid and alkali electrolyte. The electrocatalyst of cobalt@cobalt phosphide nanoparticles is grown on carbon nanotubes (Co@CoP/CNT) and shows a current density of 10 mA cm−2 at an overpotential of 67 mV in acid and 125 mV in alkali, demonstrating the strong metal-metal phosphide interaction facilitating hydrogen reduction. However, the in situ formed cobalt@cobalt oxide (Co@Co3O4/CNT) electrocatalysts from the Co@CoP/CNT can retard both the HER and OER performances through the metal-metal oxide interaction. The underlying mechanisms of the activity and selectivity of the core-shell catalysts towards water splitting reactions is further unveiled by density functional theory (DFT) simulation. The different catalytic behaviors of the core-shell structured catalysts in HER and OER are attributed to the different interactions between the metallic cores, shells and the adsorbed intermediate species. This study not only promises a facile and general strategy to fabricate high performance electrocatalysts but also sheds new light on crucial design principles of catalyst materials for intermediate-selective electrocatalytic reactions.