Importance of Au nanostructures in CO2 electrochemical reduction reaction.

Based on experimental and theoretical results, we find that the high-index (2 2 1) facets and the low-coordinated edge sites of gold nanoparticles are more favorable for the reduction of CO 2 to CO by comparing the performance of Au colloids with Au trisoctahedron of different sizes. Electrochemical conversion of CO 2 into fuels is a promising means to solve greenhouse effect and recycle chemical energy. However, the CO 2 reduction reaction (CO 2 RR) is limited by the high overpotential, slow kinetics and the accompanied side reaction of hydrogen evolution reaction. Au nanocatalysts exhibit high activity and selectivity toward the reduction of CO 2 into CO. Here, we explore the Faradaic efficiency (FE) of CO 2 RR catalyzed by 50 nm gold colloid and trisoctahedron. It is found that the maximum FE for CO formation on Au trisoctahedron reaches 88.80% at −0.6 V, which is 1.5 times as high as that on Au colloids (59.04% at −0.7 V). The particle-size effect of Au trisoctahedron has also been investigated, showing that the FE for CO decreases almost linearly to 62.13% when the particle diameter increases to 100 nm. The X-ray diffraction characterizations together with the computational hydrogen electrode (CHE) analyses reveal that the (2 2 1) facets on Au trisoctahedron are more feasible than the (1 1 1) facets on Au colloids in stabilizing the critical intermediate COOH*, which are responsible for the higher FE and lower overpotential observed on Au trisoctahedron. [ABSTRACT FROM AUTHOR]