Enhanced photoelectrochemical oxidation of alkali water over cobalt phosphate (Co-Pi) catalyst-modified ZnLaTaON₂ photoanodes

Zinc lanthanum tantalum oxynitride [ZnLaTaON₂] powders were synthesized by conventional solid state reaction. ZnLaTaON₂ photoelectrodes were prepared by electrophoretic deposition of ZnLaTaON₂ suspension in acetone onto ITO substrate. The photoelectrodes of ZnLaTaON₂ were established to reveal photoelectrochemical properties for water oxidation reaction. Moreover, a cobalt phosphate (Co-Pi) was loaded on ZnLaTaON₂ photoelectrodes via photodeposition method to enhance the photoelectrochemical water oxidation performances. Photocurrent voltage characteristics of the Co-Pi/ZnLaTaON₂ photoelectrodes were enhanced with its effect which is more evidenced at lower water oxidation potentials. A relatively stable photocurrent density of 5 mA/cm² at 1.5 V vs RHE was attained with the support of electron donor in alkaline phosphate solution. Comparatively, in Co-Pi/ZnLaTaON₂ photoelectrodes, approximately threefold enhancement was noticed at 1.8 V_RHE in assessment with parent photoelectrode. On the other hand, Co-Pi/ZnLaTaON₂ photoelectrodes have been shown as an alternative pathway to improve the photoelectrochemical current gain through the PEC water oxidation reaction.