Photocatalytic H2 evolution over Ni3(PO4)2/twinned-Cd0.5Zn0.5S S-scheme homo-heterojunction using degradable plastics as electron donors

Abstract

The development of catalysts that can efficiently separate both bulk and interface charges is crucial for conversion and utilization of solar energy. In this study, a homo-heterojunction was fabricated by combining twinned-Cd_0.5Zn_0.5S (T-CZS) and Ni₃(PO₄)₂ with crystalline water (NiPO) using a solvent evaporation strategy for efficient photocatalytic H₂ evolution in water containing degradable plastics. The bulk phase of T-CZS consists of wurtzite Cd_0.5Zn_0.5S (WZ-CZS) and zinc blende Cd_0.5Zn_0.5S (ZB-CZS), they exhibit a slight difference in energy range and can form S-scheme homojunction, while NiPO and T-CZS constitute the S-scheme heterojunction, they work together to promote the separation of bulk and interface charges. This double S-scheme homo-heterojunction achieves a hydrogen evolution rate ($r_{{\mathrm{H}}_2}$) of 73.2 mmol h⁻¹ g⁻¹ over 8% NiPO/T-CZS in a solution mainly composed of polylactic acid (PLA), which exhibits an increase by factors of 243.0 and 4.5 compared to NiPO and T-CZS individually. Meanwhile, PLA plastics are degraded into organic chemicals including formic acid, acetic acid, and pyruvic acid. Moreover, NiPO exhibits (localized surface plasmon resonance) LSPR effect, which can broaden the light absorption range of the system, reduce the H₂ evolution overpotential, and enhance electron utilization efficiency. Based on electron capture experiments and band theory analysis, the introducing of plastic as an electron donor further accelerates the evolution process of H₂, while alkaline sodium hydroxide (NaOH) solution promotes the PLA dissociation and enhances oxidation driving force, indirectly promoting the H₂ evolution kinetics of this system. The present research offers prospective solutions for engineering solar-powered H₂ evolution to tackle energy challenges.