P-n heterojunctions of Si@WO3 mimicking thylakoid for photoelectrocatalytic CO2 reduction to C2+ products — Morphology control

Abstract

The photoelectrocatalytic reduction of CO2 to high value-added chemicals is considered as one of the most promising technologies for solving both environmental and energy issues of the planet. Here, p-n heterojunction nanowires Si@WO3-x derived from p-silicon wafer modified by tungsten trioxide with different morphologies, including nanosheets (NS), nanobulks (NB) and nanoneedles (NN), were designed and fabricated. The Si@WO3-NS heterojunction gives the highest apparent quantum efficiency of light (0.49 % AQE) excluding the contribution of electrons from anode (>0.4 % QE of nature plant), which is nearly 25 times than that of pure Si NW (0.02 % AQE). The selectivity of multicarbon products (C2+) for Si@WO3-NS catalyst reaches 62.7 %, benefiting from the morphology simulated to the structure of thylakoid in plants. Moreover, the mechanism was proposed and confirmed by operando FT-IR experiments indicating the existence of active species COO−, HCOO−, C−O and C−C, respectively. This engineering design for Si-based material simulated plant cell can firstly produce C2+ chemicals without assistance of copper particles known as good catalyst or co-catalyst for C−C coupling.