Engineering Work-Function-Gradients-Induced Co ₃ O ₄ → CdS → NiO/SnO ₂ Dual Charge Transfer Channels To Synergistically Boost Photocatalytic Hydrogen Evolution

Realizing efficient spatial charge separation is pivotal yet challenging for advancing solar-driven photocatalytic H 2 evolution. Here, a dual-channel charge transfer configuration (Co 3 O 4 → CdS → NiO/SnO 2 ) is engineered onto CdS nanorods through work-function gradients induced unidirectional charge transfer. The optimized 2%SnO 2 -4%NiO-2%Co 3 O 4 –CdS achieves a markedly H 2 evolution rate of 19.73 mmol·h –1 g –1, representing a 12.4-fold enhancement over pristine CdS (1.59 mmol h –1 g –1 ) and outperforming single channel 4%NiO-2%Co 3 O 4 –CdS (12.6 mmol h –1 g –1 ) and 2%SnO 2 -2%Co 3 O 4 –CdS (7.37 mmol h –1 g –1 ) by factors of 1.6 and 2.7, respectively. Synchronous illumination X-ray photoelectron spectroscopy, work function analyses, and charge density difference verify that the unique dual-channel charge transfer configuration of SnO 2 –NiO–Co 3 O 4 –CdS realizes superior spatial charge separation. Photoelectric measurements elucidate that dual channels work synergistically to accelerate charge transfer dynamics, exhibit a higher charge migration rate ( k ET ) and efficiency (η ET ) than single channel counterparts. Density functional theory calculations further demonstrate that the d-band center of Ni and the p-band center of Sn in a dual-channel configuration can be cooperatively tuned closer to the Fermi level, thereby promoting the adsorption of H 2 O molecules. Together with the optimized *H adsorption/desorption behavior exhibited by SnO 2 –NiO–Co 3 O 4 –CdS, these factors collectively underlie its outstanding H 2 evolution performance. This study emphasizes a rational design strategy toward high-performance photocatalysts through engineering dual-charge transfer channel networks.