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 : H₂ = 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.