Photoelectrochemical (PEC) water splitting shows promising potential for green hydrogen production. However, it currently lacks the technological readiness to allow commercialisation due to limitations in material performance, particularly in developing a scalable, efficient photoanode. 𝛂-Fe₂O₃ (Commonly known as Hematite), BiFeO₃, and BiVO₄ are all semiconductor photoanode materials with great potential due to their desirable bandgap sizes and positionings, yet they face issues to varying degrees with electron-hole recombination rates and slow charge transport¹. Charge carrier dynamics are significantly influenced by a material's phase purity and morphology. Developing a scalable fabrication technique that promotes high phase purity and favourable morphology is therefore essential. Aerosol assisted chemical vapour deposition (AACVD) is a method of depositing semiconductor thin films that has had relatively little reporting in the field of PEC. Unlike other classes of chemical vapour deposition, AACVD does not require volatile precursors, thus allowing precursors to be more tailored towards producing highly efficient, specifically designed photoelectrodes².

Herein, we report some of the first instances of depositing phase pure 𝛂-Fe₂O₃, BiFeO₃, and BiVO₄ via AACVD. A ‘Universal’ precursor approach was taken, in which a common ligand framework based upon an amino-tris alcohol was utilised on various metal centres. By aligning precursors at molecular level, complementary decomposition pathways could be achieved, enabling the development of dual-source precursors to deposit mixed metal oxides of high phase purity. Each precursor was synthesised under inert conditions, with their structure and purity confirmed via single-crystal X-ray diffraction, ¹H NMR, ¹³C NMR, and elemental analysis. The suitability of each compound as an AACVD precursor was assessed using thermogravimetric analysis (TGA). By studying TGA results, our dual-source precursors were effectively matched together based on compatibility/overlap in decomposition pathway. All three materials were deposited on FTO substrate at a temperature <500^oC, with subsequent annealing in air at 500-650^oC. Compositional analysis of the films was carried out using powder X-ray diffraction, Raman spectroscopy, and energy dispersive X-ray spectroscopy. These techniques confirmed that in all cases, phase pure films of 𝛂-Fe₂O₃, BiFeO₃, and BiVO₄ were produced. Scanning electron microscopy revealed distinctive morphologies: 𝛂-Fe₂O₃ formed as nanoflakes, while BiFeO₃ and BiVO₄ grew as high-surface-area nanorods. Photoactivity was assessed by chopped-light linear scanning voltammetry, with the films displaying impressive activity compared to previous reporting’s for the same materials. Most notably, BiVO₄ achieved a photocurrent density of 1.25 mA.cm⁻² at 1.23 V_RHE, the highest photoactivity reported to date for BiVO₄ films synthesized via AACVD. These results suggest that the high phase purity and optimised morphologies of AACVD-derived photoanodes enhances charge carrier dynamics, leading to improved PEC performance.