Photoelectrochemical generation of H2O2 using hematite (α-Fe2O3) and gas diffusion electrode (GDE)

In contrast to the industrial-scale production of H 2 O 2 , electrochemical or photoelectrochemical synthesis is an environmentally friendly alternative. In this study, the photoelectrochemical generation of H 2 O 2 was investigated using a hematite (α-Fe 2 O 3 /FTO/glass) photoanode in combination with a gas diffusion electrode (GDE) modified by the incorporation of tin(II) phthalocyanine (SnPc) in its hydrophilic layer. The experiments were conducted in a photoelectrochemical cell with two compartments separated by a proton exchange membrane, under an applied bias and AM1.5 irradiation (100 mW/cm 2 ). The amount of H 2 O 2 generated was quantified through chemical analysis using visible light spectrophotometry of the electrolyte. To assess the process efficiency, the Faradaic efficiency ( FE ) was calculated. The optimal configuration employed air as the inlet gas for the GDE and phosphate buffer (pH 6.4) as the electrolyte in the cathodic compartment. The combination of the hematite photoanode and the GDE modified with SnPc was the most effective for H 2 O 2 photoelectrochemical generation. The highest FE values achieved were 52.4 % for the GDE (O 2 reduction to H 2 O 2 ) and 0.4 % for the hematite photoanode (H 2 O oxidation to H 2 O 2 ). • H 2 O 2 generated via oxygen reduction reaction (ORR) and water oxidation reaction (WOR). • The Faradaic efficiencies ( FE ) for H 2 O 2 photoelectrochemical generation determined. • Hematite photoanode and gas diffusion electrode (GDE) modified by tin(II) phthalocyanine used. • The highest FE of ORR on GDE was for phosphate buffer as catholyte (52 %). • FE of WOR on hematite was almost negligible showing its not favourable kinetics.