Promoting water-splitting reaction on TiO2/gCN with Pd/SrO cocatalysts: H2 evolution in the absence of a sacrificial reagent

Abstract

Depleting fossil fuel reserves and increased global warming have compelled researchers to seek a sustainable energy source. The current work presents an eco-friendly water splitting reaction on Pd–SrO@TiO₂/gCN photocatalysts. The catalysts reported herein have been synthesized using hydrothermal treatment, whereas cocatalyst (i.e. Pd/SrO) integration on graphitic carbon nitride (gCN) and rutile TiO₂ have been successfully completed via chemical reduction. The morphology and optical properties of the catalysts have been analyzed using XRD, Raman, FTIR, UV-Vis/DRS, PL, and SEM/EDX. The chemical composition, surface properties, electrochemical behaviour, and particle sizes were examined by XPS, EIS, AFM and BET technique followed by hydrogen evolution experiments. Evaluation of the sunlight-driven hydrogen generation activity of TiO₂, gCN, TiO₂/gCN, SrO@TiO₂/gCN, Pd@TiO₂/gCN, and Pd–SrO@TiO₂/gCN photocatalysts has been conducted and justified. The results reveal that the influence of TiO₂/gCN staggered band alignment, Schottky effect by palladium, metal/semiconductor interface engineering and elevation of Fermi energy level by the strontium oxide have efficiently enhanced the photocatalytic H₂ generation under sunlight. This study demonstrated no use of additional sacrificial reagents to prevent the back reactions and toxic side products where SrO reformed itself after consuming the holes during photoreaction. The combination of Pd and SrO was accountable for the maximum charge separation and relatively higher H₂ evolution on Pd–SrO@TiO₂/gCN catalysts that delivers 24.5 mmol g⁻¹ h⁻¹ of hydrogen. It is inferred that the aforementioned approach has potential to replace the conventional and costly catalysts used in hydrogen generation technologies.