Synergistic effect of Cu/Ni cocatalysts on CdS for sun-light driven hydrogen generation from water splitting

Abstract

High cost and depletion of fossil fuels obligate the researchers to find energy sources that are not only renewable but can also replace the conventional sources. In this work, various catalysts namely, CdS, Cu@CdS, Ni@CdS and Cu/Ni@CdS were synthesized by the hydrothermal technique. To enhance the activity and stability, Cu/Ni cocatalysts were in-situ deposited over CdS surfaces by chemical reduction method. As-prepared catalysts were employed for photoreaction to generate hydrogen from water-splitting. The optical characteristics of catalysts were determined by UV-VIS/DRS and PL techniques. Morphology of catalysts was evaluated by XRD, Raman, SEM and AFM analysis. The surface properties and elemental compositions were justified via EDX and XPS analysis. Comparative H2 generation activities were monitored at GC-TCD (Shimadzu-2010). Results depict that an optimized ratio of cocatalysts (i.e. 2% Cu and 1% Ni) over the CdS exhibits higher H2 evolution activities (i.e. 14.16 mmol g−1 h−1 with 72% quantum efficiencies). Higher activities were attributed to synergism between Cu and Ni cocatalysts. The Cu cocatalysts supplement the electron populations over the CdS surfaces by surface plasmon resonance, whereas Ni cocatalysts suppress the back reaction due to the formation of Schottky junctions. The photocatalytic H2 productions were optimized for various factors such as, pH, temperature, photocatalyst dosage and light intensity. On the basis of results, it could be concluded that this research will add new promises for renewable energy applications.