A solar-charged photoelectrochemical wastewater fuel cell for efficient and sustainable hydrogen production

Abstract

It is of great practical significance to realize the efficient treatment of wastewater and the comprehensive utilization of chemical energy from wastewater. Therefore, a WO₃ NFs–C/Cu₂O nanowire arrays (NWAs) visible-light response dual-photoelectrodes solar-charged photoelectrochemical wastewater fuel cell (scPEWFC) was constructed for efficient hydrogen production based on the promotion of phenol oxidation at the anode. The hydrogen production reaches as high as 93.08 μmol cm⁻² by the photoelectrocatalytic oxidation of phenol (TOC removal rate reached 82.12%) of WO₃ NFs–C/Cu₂O NWAs under visible light irradiation for 8 h without additional bias, which is 3.02 times higher than that of pure photocatalytic water splitting. The excellent photoelectrochemical performance can be attributed to the less endergonic process of phenol oxidation compared to water oxidation, which indicated that phenol oxidation can promote the hydrogen generation at the cathode. Isotopic labelling experiments show that protons were derived from the splitting of water rather than phenol. Interestingly, WO₃ (with great electrons storage property) and photoelectrochemical cell (PEC) were combined to construct a scPEWFC, the hydrogen production (4 h to produce 7.50 μmol cm⁻²) was still carried out at the cathode under the dark owing to the stored electrons of WO₃ under the light, which realized the ideal effect of full-day and high-efficiency hydrogen production. Besides, the mechanism of scPEWFC operation was investigated in detail. This paper provides a new research idea for scPEWFC wastewater treatment, energy recovery, electron storage, and simultaneous full-day hydrogen production.