CO2 reduction is a very attractive research field in environmental, material, and chemical science in light of the energy crisis and the greenhouse effect. In this study, Bi2WO6/BiOCl heterojunctions were fabricated onto the F-SnO2 transparent conductive glass in situ by a hydrothermal method. These new photocathodes, named BCW-X, were characterized by such methods as scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscope, and UV-vis spectra. Their morphology is a good 2D layered/3D flower structure. The exposed crystal plane of BiOCl was changed from (1 0 1) of the pristine form to (1 1 2) in the heterojunction. The photoelectrocatalytic reduction of CO2 was carried out in BCW-X vertical bar KFICO3 vertical bar BiVO4 under irradiation by an Xe lamp and external voltage from a Si solar cell (-0.6 to -1.1 V). A PEC cell of BCW-6 vertical bar KHCO3 vertical bar BiVO4 produces ethanol at a rate of 11.4 mu M h(-1) cm(-2) (600 mu mol h(-1) g(-1) ) with 80.0% selectivity under -1.0 V. The apparent quantum efficiency is up to 0.63%, about three times that of composite BiOCl-Bi2WO6 as photocathode. These phenomena can be attributed to the better photogenic electron-hole separation and high charge separation efficiency of heterojunctions. (C) 2019 Elsevier Inc. All rights reserved.