Hydrogen production from photo-driven electrolysis of biomass-derived oxygenates: A case study on methanol using Pt-modified WO3 thin film electrodes

In this paper, we demonstrate the feasibility of H2 production from biomass-derived oxygenates with photoelectrochemical cells (PECs) based on the tandem cell hybrid photoelectrode configuration. As a proof of concept, we have studied the simplest oxygenate, methanol, which is photoelectrochemically oxidized at thin film tungsten oxide (WO3) photoelectrodes. When the methanol oxidation reaction (MOR) is coupled with the hydrogen evolution reaction (HER), this process is known as methanol electrolysis. We demonstrate that catalytic modification of the WO3 surface by the electrodeposition of Pt particles can greatly increase MOR activity at the photoanode, resulting in a significant increase in H2 production rates from methanol electrolysis. This improvement is greatest at low overpotentials and high Pt loadings, with the demonstrated MOR current density of Pt–WO3 being nearly four times that of the oxygen evolution reaction (OER) on WO3 at a potential of 0.8 V vs. the Reversible Hydrogen Electrode. We also illustrate how the increase in WO3 photocurrent and the decrease in the oxidation onset potential, compared to the OER, make it possible to use WO3-based photoelectrodes in a simple tandem cell configuration whereby a common PV component such as a-Si can provide the remaining voltage to achieve unassisted methanol electrolysis. Results from methanol electrolysis reveal the potential to utilize a similar approach for larger biomass-derived oxygenates, which could be a promising pathway to H2 production from renewable feedstock using photo-driven electrolysis.