Interfacial properties of Co3O4/Gd–Fe2O3 p-n junction photoanode improved by PDDA functional layer for efficient photoelectrochemical water oxidation

Abstract

The phase interface properties of the p-n junction may profoundly affect its photoelectrochemical (PEC) water oxidation performance. Here, we introduced a non-conjugated polymer functional layer (poly(diallyl-dimethylammonium chloride, PDDA) between the interfaces of the p-n junction (Co3O4/Gd–Fe2O3) to tune the interfacial properties. First, the PDDA modulates the band structure so that the composite photoanode (Co3O4/PDDA/Gd–Fe2O3) has an enlarger band bending than the p-n junction. Then, PDDA passivates the surface trap, which synergizes with Co3O4 to provide more active sites for water oxidation. Furthermore, PDDA improves the PEC water oxidation kinetics. Specifically, PDDA extracts holes and adsorbs water oxidation reactants, thus it efficiently transfers photogenerated holes to Co3O4, promoting the water oxidation reaction in the positive direction. With these positive modulations, PDDA can further enhance the PEC water oxidation performance of the p-n junction. This conceptual work provides insight into the role of the non-conjugated polymer in PEC water splitting.