Generation of fuel from CO2 saturated liquids using a p-Si nanowire ‖ n-TiO2 nanotube array photoelectrochemical cell

Abstract

Light-driven, electrically biased pn junction photoelectrochemical (PEC) cells immersed in an electrolyte of CO₂ saturated 1.0 M NaHCO₃ are investigated for use in generating hydrocarbon fuels. The PEC photocathode is comprised of p-type Si nanowire arrays, with and without copper sensitization, while the photoanode is comprised of n-type TiO₂ nanotube array films. Under band gap illumination, the PEC cells convert CO₂ into hydrocarbon fuels, such as methane, along with carbon monoxide and substantial rates of hydrogen generation due to water photoelectrolysis. In addition to traces of C3–C4 hydrocarbons, methane and ethylene were formed at the combined rate of 201.5 nM/cm²-hr at an applied potential of −1.5 V vs. Ag/AgCl. The described technique provides a unique approach, utilizing earth abundant materials, for the photocatalytic reduction of CO₂ with subsequent generation of higher order hydrocarbons and syngas constituents of carbon monoxide and hydrogen.