Simultaneous Laser Ablation and Carbon Coating of ZnO Nanospheres for High-Performance Photoelectrocatalysis

Zinc oxide has been extensively studied for its photocatalytic and photoelectrocatalytic applications due to its wide-bandgap (3.37 eV) and strong response to ultraviolet (UV) light. However, its practical application is hindered by intrinsic limitations such as poor visible light absorption, poor electrical conductivity, rapid charge carrier recombination, and environmental photocorrosion. The synthesis of these carbon-coated ZnO nanospheres via laser ablation of ZnO nanorods presents an approach for enhancing photoelectrocatalytic performance. In this study, ZnO nanorods were first synthesized via a reflux method and subsequently subjected to laser ablation mixed with a carbon precursor, leading to the formation of these carbon-coated ZnO nanospheres. The structural, morphological, and compositional characteristics of the synthesized (ZnO@C) nanospheres were analyzed using X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy. The optical response in the UV–vis shows an appreciable increase in the absorbance for the sample after carbon coating on ZnO. To validate the observation, an finite-difference time-domain (FDTD) simulation was carried out, showing a notable increase in absorption intensity (∼84%) compared to pristine ZnO. In electrochemical tests, the thin carbon coating reduces the overpotential for the hydrogen evolution reaction (HER) and leads to a 5-fold increase in photocurrent under illumination, highlighting enhanced photoresponse through improved charge separation and transport. The Faradaic efficiency of hydrogen production of the composite increased to 69.4% under light irradiation compared to 41.6% in dark conditions, demonstrating the superior catalytic efficiency of the ZnO@C composite in light. The carbon coating improves electrical conductivity, effectively reducing charge recombination losses, provides structural stability, protects the ZnO from environmental degradation, and enhances electrode longevity. This work demonstrates that laser ablation provides a facile and effective strategy for advanced nanostructures, opening possibilities for advanced energy and environmental applications.