Enhanced photoelectrochemical CO2 reduction activity towards selective generation of alcohols over CuxO/SrTiO3 heterojunction photocathodes

Abstract

Photoelectrochemical reduction (PECR) of CO₂ to value-added chemicals and fuels will reduce the dependency on fossil fuels, also it will solve environmental issues that arise due to greenhouse gases. A heterojunction of Cu_xO/SrTiO₃ with varying post-annealing temperature ranges from 300 to 600 °C (CS300-600) was synthesized by overlying the spin-coated SrTiO₃ on electrodeposited Cu₂O over the FTO glass substrate. The synthesized photoelectrode's crystallinity and phase formation significantly varied by varying the post-annealing temperature, which was characterized via XRD and Raman spectroscopy. Optical, morphological, type of heterojunction formation and elemental surface oxidation states of photoelectrodes were studied through UV–visible DRS spectrum, FE-SEM, and XPS analysis respectively. Electrocatalytic analysis such as Linear Sweep Voltammetry (LSV), and Electrochemical Impedance Spectrometry (EIS) was employed, thus it conforms to the highest photocurrent density (−1.38 mA/cm² at −0.6V vs. Ag/AgCl), and low charge transfer resistance (R_CT=0.412 kΩ) at the electrode-electrolyte interfaces for CS500 photoelectrode as compared to others photoelectrodes. PECR of CO₂ to liquid product formation was evaluated by applying different potential ranges (0 to −0.6 V vs. Ag/AgCl). Highest methanol formation of 48.69 μmol.cm⁻²hr⁻¹, which is approximately 9 times enhanced as compared to the pure Cu₂O (5.62 μmol.cm⁻²hr⁻¹) photoelectrode at 0 V vs Ag/AgCl for CS500 heterojunction. Optimization of overlaying SrTiO₃ synthesis temperature for crystallization formation on Cu₂O and applied photoelectrode potential findings could pave the way for designing other new heterojunction types for selective liquid alcohol production.