Boosting electrocatalytic oxygen evolution using ultrathin carbon protected iron–cobalt carbonate hydroxide nanoneedle arrays

Abstract Nonprecious metal hydroxides are promising candidates for oxygen evolution reaction (OER) catalysts. Enhancing charge transfer efficiency and optimizing their surface states are crucial to further improve their OER activity for practical applications. Herein, using a facile hydrothermal reaction and low-temperature calcination process, we synthesize ultrathin carbon coated, nitrogen and iron modified cobalt carbonate hydroxide needle arrays on carbon cloth (C@NFeCoCH/CC). The synergistic effect of Fe and N modification induces high OER activity of C@NFeCoCH/CC and a conversion of rate determining step for OER, which mainly benefits from highly active Co/Fe–N–C species in situ formed on the interface of carbon layer and needles. Thin carbon layer, N and Fe modification, along with continuous conductive carbon cloth guarantee fast and stable charge transfer from bulk of free-standing porous catalyst film to its interface. It is found that the optimized C@NFe1Co1CH/CC exhibits a low overpotential of 235 mV at 10 mA cm−2, a mass activity of 681.4 A g−1 and a superior stability over 30 h at 10 mA cm−2. Moreover, experiments demonstrate that the Co/Fe sites possess higher OER activity than the N–C sites, while the Co/Fe–N (-C) sites can obviously outperform the Co/Fe–O sites.