Unassisted photoelectrochemical CO2 reduction by employing III–V photoelectrode with 15% solar-to-fuel efficiency

Abstract

Solar-driven carbon dioxide reduction reaction (CO₂RR) provides an opportunity to produce value-added chemical feedstocks and fuels. However, achieving efficient and stable photoelectrochemical (PEC) CO₂RR into selective products is challenging owing to the difficulties associated with the optical and the electrical configuration of PEC devices and electrocatalyst properties. Herein, we construct an efficient, concentrated sunlight-driven CO₂RR setup consisting of InGaP/GaAs/Ge triple-junction cell as a photoanode and oxide-derived Au (Ox-Au) as a cathode to perform the unassisted PEC CO₂RR. Under one-sun illumination, a maximum operating current density of 11.5 mA cm^–2 with an impressive Faradaic efficiency (FE) of ~98% is achieved for carbon monoxide (CO) production, leading to a solar-to-fuel conversion efficiency of ~15%. Under concentrated intensity of 10 sun, the photoanode records a maximum current density of ~124 mA cm^–2 and maintains ~60% of FE for CO production. The results demonstrate crucial advancements in using III–V based photoanodes for concentrated PEC CO₂RR.