Nickel-substituted polyoxometalate-CdS single-cluster photocatalysts for efficient plastic waste degradation coupled with H₂ production

The photocatalytic degradation of plastic waste represents a pivotal strategy for mitigating the global plastic pollution and fostering resource-efficient utilization. Herein, a facile impregnation method was used to uniformly load various Ni-substituted polyoxometalates (Ni-POMs) onto CdS nanospheres and thus obtain a series of single-cluster Ni-POM@CdS photocatalysts. During visible-light irradiation for 10 h, the catalyst with the highest synergistic photoredox performance (Ni₉@CdS-10) achieved an exceptional extent of polylactic acid degradation and H₂ productivity (22.29 mmol·g_cat⁻¹) exceeding that of pristine CdS ~ 160-fold. The generation of pyruvate—a versatile and valuable chemical—as a degradation product (19.01 mmol·g_cat⁻¹) rendered the process highly economically viable. Systematic control experiments and comprehensive characterization analyses indicate that the photocatalytic degradation of plastic waste by Ni₉@CdS-10 proceeds via a charge transfer–mediated mechanism, with the Ni₉ clusters acting as electron sponges and efficiently extracting photogenerated electrons from CdS to promote H₂ evolution while facilitating hole-dominated plastic oxidation. This work provides valuable insights into the development of plastic waste degradation processes promoted by Ni-POM photocatalysts and establishes a practical strategy for converting plastic waste into fuels and chemicals.