Phosphate ions interfacial drift layer to improve the performance of CoFe-Prussian blue hematite photoanode toward water splitting

Charge recombination at the surface of hematite photoanode is among the main issues that diminish its photoelectrochemical (PEC) water splitting efficiency. Herein, we address this issue by anchoring phosphate ions (Pi) layer between hematite's surface and CoFe-Prussian blue analogue (CoFe-PBA) water oxidation catalyst (WOC). The PEC results revealed that the Pi interfacial layer is crucial for boosting the PEC activity of CoFe-PBA/hematite photoanode. It improves the activity by 2.9-fold at 1.23 V-RHE. The analysis of time and frequency-resolved results revealed that the synergy between the Pi layer and CoFe-PBA catalyst prolongs the photogenerated holes lifetime, reduces their charge transfer resistance, and suppresses the surface recombination. The DFT simulations suggested that the Pi interfacial layer drifts the electrostatic potential of the hematite's surface toward more negative potential and thus facilities the diffusion of the photogenerated holes toward the hematite/CoFe-PBA/electrolyte interfaces making them dynamically apposite to oxidize water on CoFe-PBA WOC.