S-Scheme α-Fe2O3/TiO2 Photocatalyst with Pd Cocatalyst for Enhanced Photocatalytic H2 Production Activity and Stability

In this work, hematite with titanium dioxide (α-Fe2O3/TiO2) heterojunctions with palladium (Pd) nanoparticles were synthesised to improve efficiency of photocatalytic hydrogen production. α-Fe2O3 was loaded onto TiO2 surfaces, then Pd nanoparticles were deposited to make a ternary photocatalyst. The chemical composition, morphology and surface properties of photocatalytic ternary heterojunction were characterized by XRD, UV–Vis, FE-SEM, TEM, EDS, XPS techniques and BET analysis. The PL emission, transient photocurrent and EIS Nyquist plot were investigated for separation and migration of photogenerated charge carriers in photocatalyst nanocomposites. The average crystallite size of ternary α-Fe2O3/TiO2-Pd was 22 nm and its band gap energy was 2.00 eV, much lower than that of the pure TiO2 nanoparticles (3.16 eV). The α-Fe2O3/TiO2-Pd also has higher specific surface area and smaller EIS radius, which enhance interface activity and charge transfer. The α-Fe2O3/TiO2-Pd exhibited great performance, with H2 production rate of 3490.54 µmol h−1 g−1 and excellent stability in multi-cycle H2 production. The photocatalytic mechanism of α-Fe2O3/TiO2-Pd as explained by the S-scheme heterojunction is that the electron in the VB of α-Fe2O3 and TiO2 are transferred to CB of each photocatalyst. Then, the electrons in the CB of TiO2 are transferred to the VB of α-Fe2O3 and the photogenerated electrons in CB of α-Fe2O3 can migrate to Pd, which increase the redox ability for H2 production and increase the separation of photogenerated e−–h+ pairs. Overall, the experimental results and theoretical analyses confirm the high potential for the applicability of the ternary photocatalysts for H2 production.Graphical Abstract