Synergistic Pt-Ni Cocatalysis on Dendritic CdS Boosts Photocatalytic H2 Evolution by Promoting Charge Separation and Water Dissociation

This work targets efficient visible-light-driven hydrogen evolution by construction of a dendritic CdS-based photocatalytic system decorated with Pt-Ni bimetallic cocatalysts (CdS@PtNi). The dendritic CdS was synthesized via a hydrothermal method, followed by in situ deposition of Pt and Ni using NaBH4 chemical reduction, with cocatalyst loading tuned between 2 and 5 wt%. Among them, C@PN4 (4 wt% total metal loading) demonstrated the best performance, with a bandgap of ~2.15 eV. XRD results show that the samples retain the hexagonal CdS phase without significant impurities. SEM/TEM and elemental mapping confirm uniform dispersion of Pt and Ni, forming intimate interfaces with CdS. XPS results reveal positive shifts in S 2p and Cd 3d binding energies, indicating that the bimetallic cocatalyst promotes electron transfer from CdS to the metals and enhances interfacial coupling. Photoelectrochemical analysis shows C@PN4 features enhanced absorption above 500 nm, significantly reduced PL, extended carrier lifetime, higher transient photocurrent, and lower charge-transfer resistance, suggesting greater efficiency in charge separation and transport. Band structure analysis reveals a negative shift of the conduction band to a more reductive potential. In photocatalytic tests, C@PN4 achieves an H2 yield of 15.6 mmol g−1 over 4 h (3.9 mmol g−1 h−1), with <5% activity loss after four cycles. AQY reaches 0.0483% at 420 nm, with a monochromatic photon-to-hydrogen conversion efficiency (MPH) of up to 2.01%. Mechanistically, the Pt/CdS Schottky junction drives directional electron extraction, while Ni likely synergistically optimizes interfacial electronic distribution and facilitates water activation/dissociation; together, they accelerate surface reaction kinetics and suppress photocorrosion, achieving efficient and stable hydrogen evolution with low noble metal loading.