Strain effect on the catalytic activities of B- and B/N-doped black phosphorene for electrochemical conversion of CO to valuable chemicals

Abstract

Electrocatalytic conversion of CO to valuable chemicals, such as CH₄, CH₃OH and C₂H₄ with higher energy density and wider applicability, is a more attractive way to alleviate the current energy poverty and environment pollution. However, it still remains a grand challenge to develop low cost but highly active electrocatalysts for CO reduction with high selectivity. Herein, we designed two metal-free electrocatalysts, namely boron doped and boron–nitrogen co-doped 2D black phosphorene (B@BP and B–N@BP, respectively), for reducing CO to high value-added chemicals, by means of density functional theory (DFT) calculations. Our results reveal that applying compressive strain along the armchair direction of the two designed catalysts can effectively enhance the catalytic activity while regulate the reaction selectivity of CO reduction. On B@BP without strain, CO can be reduced to CH₄ with a limiting potential of −0.55 V. However, the final product on B@BP with 7% compressive strain is almost completely changed from CH₄ to CH₃OH with a lower limiting potential of −0.38 V. As for B–N@BP, applying a 7% compressive strain can promote CO coupling and subsequently reduce CO-dimer to CH₂CH₂ with an extremely low limiting potential of −0.22 V. Importantly, the enhanced catalytic activity can be attributed to the strain induced downshift of unoccupied p-orbital of B-dopant towards the Fermi level, which facilitates to activate the adsorbed CO molecule and promote the C–C coupling. Therefore, the as-designed metal-free electrocatalysts in combination with strain engineering offer cost-effective opportunities for advancing sustainable carbon-based chemicals and fuels production.