N-doped carbon-encapsulated nickel on reduced graphene oxide materials for efficient CO2 electroreduction to syngas with potential-independent H2/CO ratios

Abstract Electrochemical CO2 reduction (ECR) is a sustainable method for obtaining syngas, which is largely desired for producing high energy-dense hydrocarbons and alcohols through the industrialized process. However, it is still a challenge to adjust the H2/CO ratio in a wide range while holding a large current density. Guiding by the density functional theory (DFT) calculations, the electrocatalyst of N-doped carbon-encapsulated metallic Ni particles supported on reduced graphene oxide (Ni@N-C/rGO) is developed for ECR to tunable syngas. The quantitative Ni@N-C responses to the controllable catalytic activity of ECR to CO, while the rGO serves as both HER catalyst and support of Ni@N-C. The Ni@N-C/rGO material exhibits high CO2 reduction activity and stability, thereby achieving a specific current of 23 mA cm-2 and CO Faradaic efficiency (FE(CO)%) of 90% at -0.97 V vs. RHE. More importantly, the H2/CO ratio of the syngas can be adjusted in a large range of 9/1 to 1/9 without potential-dependence while maintaining large current densities (>15 mA cm-2).