The plasmonic effect of Cu on tuning CO 2 reduction activity and selectivity.

Copper (Cu) has been widely used for catalyzing the CO 2 reduction reaction (CO 2 RR), but the plasmonic effect of Cu has rarely been explored for tuning the activity and selectivity of the CO 2 RR. Herein, we conducted a quantitative analysis on the plasmon-generated photopotential ( E hv ) of a Cu nanowire array (NA) photocathode and found that E hv exclusively reduced the apparent activation energy ( E a ) of reducing CO 2 to CO without affecting the competitive hydrogen evolution reaction (HER). As a result, the CO production rate was enhanced by 52.6% under plasmon excitation when compared with that under dark conditions. On further incorporation with a polycrystalline Si photovoltaic device, the Cu NA photocathode exhibits good stability in terms of photocurrent and syngas production (CO : H 2 = 2 : 1) within 10 h. This work validates the crucial role of the plasmonic effect of Cu on modulating the activity and selectivity of the CO 2 RR.