Charge Separation Engineering via ZnCdS/CoNiPPc Schottky Heterojunction to Achieve Efficient Photocatalytic Hydrogen Evolution Coupled with Benzaldehyde Production.

Abstract

To address common challenges in photocatalytic water splitting for hydrogen (H2) production, such as slow hole consumption kinetics and uncontrolled oxidative side reactions, we have designed an innovative Zn0.5Cd0.5S/bimetallic cobalt/nickel polyphthalocyanine (denoted as ZCS/CoNiPPc) photocatalyst that forms a Schottky heterojunction. Notably, the ZCS/CoNiPPc-2 composite achieves highly efficient photocatalytic H2 evolution coupled with selective oxidation of benzyl alcohol to benzaldehyde (BAD), delivering high production rates of 40.3 mmol g-1 h-1 for H2 and 56.1 mmol g-1 h-1 for BAD, which are 3.7 and 1.6 times greater than that of pristine ZCS, respectively. Furthermore, experimental and density functional theory results confirm that the synergistic combination of the bimetallic polyphthalocyanine and the Schottky heterostructure enables directional spatial separation and rapid transport of photogenerated charge carriers while preserving the innate reduction capability of CoNiPPc and the oxidation selectivity of ZCS. This work offers a new route toward integrated photocatalytic systems capable of simultaneous hydrogen fuel generation and high-value-added organic synthesis.