In situ preparation of cobalt@N-doped porous carbon bifunctional electrocatalyst for efficient overall water splitting

Developing highly efficient noble-metal-free bifunctional nanocatalysts for electrocatalytic water splitting is attractive but challenging. Notably, the rational structure engineering could effectively promote electronic transfer and improve the active area. Herein, a free-standing N-doped porous carbon nanosheet arrays encapsulated with metallic Co nanoparticles electrocatalyst (Co@NC-A) for overall water splitting was designed via pyrolysis process followed with acid treatment. The N-doped carbon matrix not only enhances electron mobility and protects the metallic Co nanoparticles from electrolyte corrosion, but also improves the electrochemically active area and facilitates mass transfer. Consequently, the Co@NC-A exhibits superior electrocatalytic performance toward OER (η10 = 270 mV) and HER (η10 = 162 mV) in 1 M KOH. Moreover, the Co@NC-A as a bifunctional catalyst in overall water splitting could approach 10 mA cm−2 at a cell voltage of 1.66 V and operate stably for 50 h. Combined with the density functional theory (DFT) calculations, the improvement of the HER and OER activities is also attributed to the modified electronic structure with N-doped carbon and the optimized free energy toward the adsorption/desorption of intermediates. This work provides a novel and facile non-precious metal catalyst for water splitting and should be instructive for designing more carbon-based nanocatalysts.