Complete solar-driven dual-photoelectrode fuel cell for water purification and power generation in the presence of peroxymonosulfate

Highlights: • A complete solar-driven dual-photoelectrode fuel cell is developed. • The peroxymonosulfate (PMS) improves thermodynamic properties of Cu₂O photocathode. • Radical (OH• and SO₄^{• -}) and non-radical (surface complexs) pathway are responsible for 4-chlorophenol (4-CP) removal. This study reports the development of complete solar-driven dual-photoelectrode fuel cell (PFC) based on WO₃ photoanode and Cu₂O photocathode with peroxymonosulfate (PMS) serving as cathodic electron acceptor. As indicated by photoelectrochemical measurements, the PMS was able to improve thermodynamic properties of photocathode, achieving an increased open circuit potential from 0.42 V to 0.65 V vs standard hydrogen electrode (SHE). Under simulated sunlight irradiation (~100 mW cm⁻²), the maximum power density of 0.12 mW cm⁻² could be obtained at current density of 0.34 mA cm⁻², which was 8.57 times of that produced by PFC without PMS (0.014 mW cm⁻²). Correspondingly, adding PMS (1.0 mM) increased overall removal efficiency of 4-chlorophenol (4-CP) from 39.8% to 96.8%, accounting for the first-order kinetic constant (k=0.056 min⁻¹) being 6.67 times of that in the absence of PMS (k=0.0084 min⁻¹). Radical quenching and electron spin-resonance (ESR) results suggested the contribution of free radicals (• OH and SO₄^{• -}) and non-radical pathway associated with direct activation of PMS by Cu₂O photocathode. Fourier transformed infrared (FTIR) analysis confirmed the strong non-radical interaction between Cu₂O photocathode and PMS, resulting in 4-CP removal via activation of PMS by surface complex on Cu₂O. The proof-in-concept complete solar-driven dual-photoelectrode fuel cell may offer an effective manner to realize water purification and power generation, making wastewater treatment more economical and more sustainable.