Meso-pore generating P doping for efficient photoelectrochemical water splitting

Hematite (Fe2O3) has been widely used as a photoanode in photoelectrochemical water splitting (PEC) for green hydrogen production. Here, for the first time, we investigate how a simple in-situ phosphorus (P) doping strategy improves the overall PEC performance of hematite with a systematic analysis of the various effects on the PEC performance. By introducing enriched FePO4 regions on the Ti-doped FeOOH surface and subsequent high-temperature annealing via P-doping, meso-porous P,Ti co-doped Fe2O3 (P,Ti-Fe2O3) nanorods were fabricated. P,Ti-Fe2O3 exhibited four-fold and two-fold increased BET surface area and electrical active area, respectively, compared to that of Ti-Fe2O3. Benefiting from the nano-structuring and efficient P doping effects [e.g., increased carrier density (Nd=3.48168 x1020 cm-3), enhanced charge separation (eta bulk= 38.7% and eta surface= 79.1%), and steeper band bending (Wd=3.910 nm)], the resulting P,Ti-Fe2O3 photoanode exhibited 94% improved photo-current density of 2.50 mA cm-2 compared to that of Ti-Fe2O3 (@ 1.23 VRHE) under 1 sun illumination. With the deposition of the NiFeOx cocatalyst, the NiFeOx/P,Ti-Fe2O3 photoanode exhibited excellent photocurrent density of 3.54 mA cm-2 (@ 1.23 VRHE) with a remarkable cathodic shift (180 mV) of the onset potential, marking the highest value among P doped hematite studies. This study suggests a new paradigm of P doped hematite with mesopores and gradient doping properties affordable in a cost-efficient way, achieving an excellent PEC water splitting performance.

Automated summary

For the first time, a simple in-situ phosphorus (P) doping strategy was used to improve the photoelectrochemical water splitting (PEC) performance of hematite. The introduction of FePO4 regions on the Ti-doped FeOOH surface and subsequent high-temperature annealing resulted in the fabrication of mesoporous P,Ti co-doped Fe2O3 nanorods. The resulting P,Ti-Fe2O3 photoanode exhibited significantly improved photo-current density, and with the deposition of the NiFeOx cocatalyst, it achieved excellent photocurrent density with a remarkable cathodic shift of the onset potential.