In-situ hydrothermally biosynthesized cocoa pod-like α-Fe2O3 photo-anode for photoelectrochemical water splitting

Hydrogen (H 2 ) is emerging as a critical future energy source, widely recognized for its renewable nature and ability to deliver clean-burning, eco-friendly energy. Photoelectrochemical water (PEC) splitting is a clean method for H 2 production. Hematite (α-Fe 2 O 3 ) is a promising material for PEC water splitting due to its suitable bandgap (∼ 2.1 eV) and stability in aqueous media. Physical methods such as sputtering, pulsed laser deposition, and chemical vapour deposition for thin film growth are very expensive and time-consuming. In this article, a simple and eco-friendly hydrothermal bio-synthesis was used to grow hematite nanoparticles (NPs) on a fluorine-doped tin oxide (FTO) substrate for application as a photo-anode for PEC water splitting. X-ray diffraction (XRD) analysis revealed a rhombohedral structure ( ̅ R 3 ̅ cH space group). The scanning electron microscope (SEM) revealed cocoa pod-like shaped particles, and Fourier Transform Infrared spectroscopy (FTIR) confirmed functional groups. The hematite photoanode achieved a photocurrent of 0.09515 mA/cm 2 at 1.23 V vs Reversible Hydrogen Electrode (RHE), an equivalent of 0.117% of solar – hydrogen conversion efficiency (STH), demonstrating potential for sustainable hydrogen production. After two months, the photocurrent reduced to 0.0893 mA/cm 2 (STH of ∼ 0.110%). This article presents an eco-friendly and sustainable nano-engineering approach for synthesizing hematite with a unique morphology that enhances the production of H 2 .