Double Active Sites in Co-Nx-C@Co Electrocatalysts for Simultaneous Production of Hydrogen and Carbon Monoxide.

The hydrogen evolution reaction (HER) by electrocatalytic water splitting is a prospective and economical route. However, the approach is severely hindered by the sluggish anodic OER, poor reactivity of electrocatalysts, and low-value-added byproducts at the anode. Herein, formaldehyde was added as an anode sacrificial agent, and a bifunctional Co-Nx-C@Co catalyst containing abundant Co-N4 sites and Co nanoparticles was successfully fabricated and evaluated as both a cathodic and an anodic material for the HER and formaldehyde selective oxidation reaction (FSOR), respectively. Co-Nx-C@Co displayed a remarkable electrocatalytic performance simultaneously for both HER and FSOR with high hydrogen (H2) and carbon monoxide (CO) selectivity. Density functional theory calculations combined with experiments identified that Co-N4 and Co nanoparticles were dominating active sites for CO and H2 generation, respectively. The coupling tactic of FSOR at the anode not only expedites the reaction rate of HER but also offers a high-efficiency and energy-saving means for the generation of valuable H2/CO syngas.