Porosity engineering of biochar‐based single‐atom Ni catalysts to promote CO2 electroreduction over a broad potential window

Abstract Developing electrocatalysts for CO 2 electroreduction with high activity and superior selectivity is extremely important and desirable from both academic and industrial perspectives. However, owing to competition with hydrogen evolution, highly efficient CO 2 reduction is mostly achieved with high CO selectivity in a narrow potential range, which is incompatible with a large cell voltage required for industrial‐level CO 2 reduction. Herein, we report an effective strategy to regulate CO 2 reduction performances of single‐atom Ni electrocatalysts over a broad potential window by engineering their pore structures (micropores, mesopores, or hierarchical pores with both micropores and mesopores). It is revealed that hierarchically pores can significantly promote CO 2 reduction efficiency of single‐atom Ni electrocatalysts. The hierarchically porous electrocatalyst achieves a maximum CO Faradaic efficiency (FE CO ) of 97.4% at −1.2 V (vs. RHE) and shows high FE CO of >85% over a broad potential window from −0.7 to −1.7 V, much superior to electrocatalysts with other pore structures. More impressively, turnover frequency of the hierarchically porous electrocatalyst increases rapidly with increasing the applied potential and reaches 50,067 h −1 at −1.7 V. Such CO 2 electroreduction promotion could be attributed to a synergistic effect of micropores for enhancing CO 2 adsorption and mesopores for facilitating rapid release of product bubbles, which significantly improves CO 2 reduction and suppresses hydrogen evolution.