Importance of Au nanostructures in CO₂ electrochemical reduction reaction

Electrochemical conversion of CO₂ into fuels is a promising means to solve greenhouse effect and recycle chemical energy. However, the CO₂ reduction reaction (CO₂RR) 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 CO₂ into CO. Here, we explore the Faradaic efficiency (FE) of CO₂RR 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.