A Tandem Photoelectrochemical Cell for Simultaneous Co-Upgrading of Biomass and Phenolic Wastewater into Dihydroxyacetone and Cyclohexanone

Abstract

Solar-driven co-conversion of biomass and phenolic wastewater into high-value-added chemicals represents a promising pathway for advancing a circular economy while mitigating environmental pollution. However, integrating these two streams into a single reactor system for simultaneous valorization remains highly challenging. Here, we report an efficient and stable photoelectrochemical (PEC) tandem cell, featuring an iron-cobalt oxychloride-decorated BiVO4 (FexCo1–xOCl/BiVO4) photoanode and a Rh nanoparticle-loaded carbon cloth (Rh/CC) cathode. This PEC tandem system enables the simultaneous solar-driven production of dihydroxyacetone (DHA) from glycerol (GLY) and cyclohexanone (CYC) from phenol. In situ characterizations and theoretical calculations confirm that Fe and Co atoms in the FexCo1–xOCl/BiVO4 photoanode function as dual active sites for adsorption and catalysis. These sites facilitate the formation of *OH and HOCH2–CHOH*–CH2OH intermediates, accelerate oxidation kinetics, and promote the selective co-production of DHA and CYC in the PEC cell. The designed PEC tandem cell delivers a photocurrent density of 2.04 mA cm–2 at 1.23 VRHE and exhibits operational stability over 50 h. Notably, the FexCo1–xOCl/BiVO4 photoanode realizes a DHA yield of 613.4 μmol cm–2 and a DHA selectivity of 60.1%, while the Rh/CC cathode produces a CYC yield of 49.1 μmol cm–2 and a CYC selectivity of 97.9%. These results demonstrate an efficient solar-driven strategy for synergistic co-production of DHA and CYC at both electrodes, providing a prototype for efficient utilization of solar energy and simultaneous valorization of biomass and phenolic wastewater into high-value chemicals.