Transparent Zirconium-doped Hematite Nanocoral Photoanode via In-Situ Diluted Hydrothermal Approach for Efficient Solar Water Splitting

To tackle the problem of bulk recombination and to solve the holes diffusion issue in hematite, the shape-guiding and in situ doping is an effective strategy. Herein, we developed a novel strategy for designing and fabricating zirconium-doped transparent hematite (Zr-Fe₂O₃(I)) photoanode through an in situ hydrothermal method and stoichiometric iron and zirconium dilution. The concentration of ZrO(NO₃)₂ and FeCl₃·6H₂O in the precursor solution effectively influenced the transparency and morphology of zirconium-doped Fe₂O₃. The XPS and TEM analyses confirms the co-existence of Zr doping and surface modification of Fe₂O₃ nanocoral diffused ZrO₂ after high temperature quenching. Synergism between the Zr doping and ZrO₂ layer facilizes the charge transfer in Zr-Fe₂O₃ nanocoral (NC) photoanodes. Among the photoanodes prepared by variously diluted concentrations of the iron and zirconium precursor, the in situ 1/32 Zr-Fe₂O₃ nanocoral (NC) photoanode achieved an excellent photocurrent density of 1.55 mA cm² at 1.23 V vs. RHE, which is about doubles than that of the conventional pristine Fe₂O₃ (P-Fe₂O₃) NR. Additionally, as result of in situ Zr doping, favorable nanocoral morphology and ZrO₂ surface modification exhibits the decreased changer transfer resistance and increased incident photon to current efficiency (IPCE) of 1/32 Zr-Fe₂O₃ NC upto 21.9%. This in situ Zr-doping and nanocoral morphology 1/32 Zr-Fe₂O₃ fulfills the requirements of both high charge separation efficiency and improved water oxidation kinetics. A novel 1/32 Zr-Fe₂O₃ (I) NC photoanode exhibits O₂ and H₂ evolution up to 69 and 138 μmol during 5 h of overall pure water splitting. This novel in situ hydrothermal dilution approach is feasible for fabricating a transparent hematite photoanode with NC morphology for practical PEC water splitting.