The reduction of CO2 into solar fuel is not only beneficial to the reduction of CO2 emission, but also beneficial to the release of energy shortage. In this study, a solar-driven photoelectrochemical reduction reaction of CO2 to methanol is conducted using a chalcopyrite p-CuInS2 thin film as a photocathode. The CuInS2 thin film is fabricated by electrodeposition of Cu-In alloy layer followed by sulfurization. With pyridinium ion as the co-catalyst, the photoelectrochemical reduction of CO2 to methanol can occur at the overpotential of 20 mV with the faradaic efficiency of 97%. (C) 2012 Elsevier B.V. All rights reserved.