The plasmonic effect of Cu on tuning CO₂ reduction activity and selectivity

Copper (Cu) has been widely used for catalyzing the CO2 reduction reaction (CO2RR), but the plasmonic effect of Cu has rarely been explored for tuning the activity and selectivity of the CO2RR. 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 CO2 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 CO2RR.