Electroreduction of CO2 to syngas with controllable H2/CO ratios in a wide potential range over Ni–N co-doped ultrathin carbon nanosheets

Abstract

The conversion of CO₂ to syngas (H₂ and CO) via electrochemical reduction has been considered a promising strategy to mitigate the greenhouse effect. However, it is a great challenge to control H₂/CO ratios over a wide voltage window. Herein, a new method of fabricating Ni–N co-doped carbon nanosheets by molten salt-assisted pyrolysis, impregnation and re-carbonization is proposed. Benefiting from their ultrathin structure and tunable Ni–N_x active site content, the H₂/CO ratios can be adjusted from 1/2 to 2/1 within a wide applied voltage range (−0.7 to −1.3 V vs. RHE). After electrochemical stability testing for 10 h, the current density and H₂/CO ratios remained almost constant, revealing robust long-term stability. This work may benefit the construction of efficient and low-budget electrocatalysts for the production of tunable syngas.