Enhanced photoelectrochemical CO2-reduction system based on mixed Cu2O – nonstoichiometric TiO2 photocathode

Abstract

Photoelectrochemical reduction of CO2 is explored here with respect to the possible production of simple organic fuels. While the photoelectrochemical system is based on p-type Cu2O semiconductor, special attention has been paid to its stabilization, intentional modification and fabrication, as well as to optimization of experimental conditions permitting control and diversification of the CO2 reduction products. Utilization of the mixed oxides photoelectrochemical system consisting of the electrodeposited, onto transparent conductive oxide (TCO) coated glass support, Cu2O catalyst and next coupled to non-stoichiometric TiO2, acting as a charge transfer enhancing layer. Such a heterojunction allows, from one side, increase density of charge carries in the conduction band of the photocathode and, on the other side, improve conductivity of the whole system. Moreover, the outer-most over-layer of Nafion is expected to facilitate attraction of CO2 (dissolved in the sodium sulfate electrolyte) at the photoelectrochemically active mixed-metal-oxides interface. Consequently, the overall photoelectrochemical efficiency is improved, and the cathodic photocurrent (related to the CO2-reduction) of ca. 1.2mA cm−2 (at 0.1V vs. RHE). The reported hierarchical (layered mixed-oxide) system consisting of copper(I) oxide and titania over-layer (covered with the Nafion outer-most film) exhibits remarkable stability with time.