Regulating the work function of silver catalysts via surface engineering for enhanced CO 2 electroreduction.

The work function can serve as a characteristic quantity to evaluate the catalytic activity due to its relationship with the surface structure of a material. However, what factors determine the influence of the work function on the electrochemical performance are still unclear. Herein, we elucidate the effect of the work function of Ag on the electrochemical reduction of CO 2 to CO by controlling the ratio of exposed crystalline planes. To this end, the exposed surface of Ag powder was regulated by high-energy ball milling and its influence on CO 2 reduction was investigated. The surface structure with more Ag(110) surface achieves higher activity and selectivity for CO production, resulting from the lower work function of Ag(110), which dramatically enhances the electron tunnelling probability during CO 2 electroreduction. We found that a higher ratio of Ag(110) to Ag(100) leads to a lower work function and thus better electrochemical activity and selectivity. This study demonstrates a promising strategy to enhance the electrochemical performance of metal catalysts through tuning their work functions via regulating exposed crystalline planes.