Unveiling the potential of Cu–Pd/CdS catalysts to supply and rectify electron transfer for H2 generation from water splitting†

Abstract

As a future fuel, obtaining hydrogen from water could be a game changer for the renewable energy sector, because it has the potential to be used as an alternative to fossil fuels. The current project has been designed to develop catalysts that can produce hydrogen from water on irradiation by sunlight. For this purpose, CdS, Cu/CdS, Pd/CdS, and Cu–Pd/CdS catalysts were successfully synthesised and utilized for hydrogen generation. The catalytic activity of pristine CdS has potentially been enhanced with Cu and Pd cocatalysts that were deposited via a chemical reduction strategy. The morphology and optical characteristics were assessed via XRD, Raman, UV-Vis/DRS, PL, SEM, HRTEM and AFM techniques. The phase purity, composition and charge transfer were confirmed by EDX, XPS and EIS studies. Under similar conditions, photoreactions and H₂ evolution experiments were performed in a quartz reactor (UK/Velp-Sci) and GC-TCD (Shimadzu, 2014), respectively. Overall, a Cu–Pd/CdS catalyst (0.2% Cu and 0.8% Pd) was found to be the most active, potentially delivering 33.71 mmol g⁻¹ h⁻¹ of hydrogen. Higher efficiencies were attributed to the existence of Cu and Pd on CdS surfaces. It has been predicted that Cu cocatalysts increase the electron densities on CdS surfaces (i.e. active sites), while Pd cocatalysts reduce the back reactions (higher charge transportation) by forming Schottky junctions. Various factors like pH, temperature, intensity of light and catalyst dose are evaluated and discussed. Based on the results and activities, it has been concluded that the described approach shows potential to replace fossil fuels.