Steric effects of CN vacancies for boosting CO electroreduction to CO with ultrahigh selectivity.

In the electrochemical reduction of CO to CO, controlling the binding of the *COOH intermediate is key to adjusting the selectivity and catalytic activity of the CO product. Herein, we report that CN vacancies were used to control the binding of the *COOH intermediate on a Co PBA-V catalyst treated by H cold plasma bombardment to improve the CORR into CO. The CN vacancies can tune the local electronic structure and coordination environment of Co-CN-Co (Co-PBA-V) with a high CO faradaic efficiency close to 100% with remarkable durability (>87 h), and a low onset overpotential of 0.17 V in CORR. The steric effects of the V can decrease the free energy barrier of the rate limiting step for the formation of *COOH which can further crack into *CO on the active site of the Co near the V. This work provides a new strategy to tune the binding of the *COOH intermediate on the catalyst surface by new vacancies of V to enhance the CORR into a single product.