Removal of SO2 on a nanoporous photoelectrode with simultaneous H2 production

Abstract

The oxidation process of SO₃²⁻ to final SO₄²⁻ is commonly required in existing desulphurization technologies. The resulting SO₃²⁻ is usually purged with air for oxidation before disposal. The energy of SO₃²⁻ to SO₄²⁻ is wasted in this process. Herein, we report simultaneous H₂ production with the removal of poisonous SO₂via a photoelectrochemical (PEC) water splitting process based on a nanoporous BiVO₄ photoanode. The enhancement of H₂ production is attributed to the lower activation energy and faster kinetics of SO₃²⁻ oxidation compared with direct oxidation of water on the photoanode. The enhancement factor is significantly higher on the nanoporous film than on the non-porous film. The removal rate of SO₂ is higher than 97%, and the absorbed SO₂ is used to produce hydrogen. A H₂ evolution rate of 29.8 μmol h⁻¹ cm⁻² on the nanoporous BiVO₄, with a high Faradaic efficiency, is obtained with removal of SO₂, which is much faster than that without SO₂ removal (0.22 μmol h⁻¹ cm⁻²). This work provides a new method for SO₂ removal with simultaneous H₂ production. The proposed method can be used either in processes involving NaOH as a desulfurization absorber, or combined with existing desulfurization technologies, such as the ammonia-based desulfurization method.