Sharp-edged pencil-like ZnO nanostructures decorated with Co3O4 nanoparticles and integrated with g-C3N4 for enhanced photoelectrochemical water oxidation

Abstract

The rational design of hierarchical semiconductor heterostructures with engineered junctions is crucial for improving photoelectrochemical (PEC) performance. Herein, sharp-edged pencil-like ZnO nanostructures uniformly decorated with Co3O4 nanoparticles and further integrated with g-C3N4, forming a heterojunction photoelectrode for PEC water oxidation, have been reported. The synergistic combination of 1D ZnO, p-type Co3O4, and 2D g-C3N4 promotes interfacial charge separation, suppresses charge-carrier recombination, and enhances visible-light absorption. The optimized ZnO-Co3O4@ g-C3N4 photoelectrode exhibited a maximum photocurrent density of approximately 1.57 mA cm− 2 at 2.0 V vs. RHE under simulated solar illumination. Moreover, the photoelectrode retained approximately 80% of its initial photocurrent after 10,000 s of continuous illumination, indicating good short-term operational stability. Electrochemical impedance spectroscopy (EIS) confirmed reduced charge-transfer resistance, while photoluminescence quenching and transient photocurrent response supported improved charge separation and suppressed electron–hole recombination. This study demonstrates that ZnO-Co3O4@g-C3N4 heterostructures can serve as promising photoelectrodes for solar-driven PEC water oxidation.