Nickel-substituted polyoxometalate-CdS single cluster catalysts for efficient photocatalytic H₂ production and plastic degradation

Photocatalytic plastic waste degradation represents a pivotal strategy for mitigating global plastic pollution and fostering resource-efficient utilization. Yet, the simultaneous consumption of the photogenerated electrons during the photocatalytic plastic degradation remains challenging. Herein, we employed a facile impregnation method to uniformly disperse various Ni-substituted polyoxometalates (Ni-POMs) on CdS nanospheres, resulting in a series of POM-CdS single cluster catalysts (Ni-POM@CdS). Among these samples, Ni₉@CdS-10 exhibits exceptional synergistic photo-redox performance, achieving a high H₂ yield of 22.29 mmol g_cat⁻¹, along with an exceptional photocatalytic polylactic acid (PLA) plastic waste degradation under 10 h irradiation. This performance represents ~160-fold enhancement in catalytic activity compared to pristine CdS. More importantly, the pyruvate, a versatile and valuable chemical, is found to be the by-product of the photocatalytic plastic waste degradation with a yield of 19.01 mmol g_cat^-1, implying the high economic viability of this process. Combining various advanced characterization and materials simulation results, it is discovered that the Ni₉@CdS-10 follows a charge-transfer-mediated reaction mechanism in photocatalytic plastic degradation, where the electron-sponge Ni₉ efficiently extracts photogenerated electrons from CdS to promote H₂ evolution, while simultaneously facilitates hole-dominated substrate oxidation for plastic degradation. This work provides a novel insights into the development of photocatalytic plastic wastes degradation using nickel-substituted POM catalysts, and establishes a practical pathway for the converting plastic waste into fuels and chemicals.