Photoelectrocatalytic reduction of CO to syngas over Ag nanoparticle modified p-Si nanowire arrays

The solar energy-driven reduction of CO 2 and H 2 O to syngas (H 2 /CO), an important platform to produce chemicals, is of significance for alleviating greenhouse gas emission and utilizing sustainable solar energy. Here, we report a facile method for the photoelectrocatalytic reduction of CO 2 and H 2 O to syngas over an Ag nanoparticle (NP) modified p-Si nanowire array catalyst. The particle size of Ag significantly influences the activity of CO 2 reduction to CO. The H 2 /CO molar ratio in reduction products can be tuned in the range from 1 to 4 by controlling the size of Ag NPs from 4.2 to 16 nm. The adsorption strength of CO on the catalyst was found to decline with the increase in the size of Ag NPs. The Ag NPs of 8.2 nm, which possess a moderate CO adsorption strength, exhibit the maximum production of CO with the H 2 /CO ratio of 2/1. Syngas with tunable H 2 /CO distribution is produced from the photoelectrocatalytic reduction of CO 2 and H 2 O over Ag/SiNWs by controlling Ag sizes.