A comprehensive review on ZnO/layered double hydroxide heterostructure as photocatalysts and photoelectrocatalysts for environmental remediation and clean energy

Zinc oxide (ZnO), a wide band-gap semiconductor, has been extensively investigated for photocatalytic and photoelectrocatalytic applications due to its high redox potential, abundance, and non-toxicity. However, its practical performance is limited by rapid charge recombination, photocorrosion, and restricted visible-light response. To overcome these drawbacks, coupling ZnO with Layered Double Hydroxides (LDHs) has emerged as an effective strategy to engineer advanced heterostructures with superior catalytic properties. LDHs offer structural flexibility, tunable cation composition, interlayer anions, and abundant hydroxyl groups that facilitate charge transport and redox reactions. The construction of ZnO/LDH heterostructures not only improves light harvesting and electron–hole separation but also enhances surface active sites and stability during photocatalysis. This review critically summarizes the recent progress in ZnO/LDH composites, including their synthesis methods, structural characteristics, interfacial charge-transfer mechanisms, and environmental applications such as organic pollutant degradation, CO2 reduction, and photoelectrochemical water splitting. Furthermore, we discuss the existing limitations, such as ZnO photocorrosion and scalability issues, and highlight future research directions focusing on green synthesis routes, defect engineering, and multifunctional heterostructures. Collectively, ZnO/LDH heterostructures represent a promising platform for next-generation photocatalytic and energy-conversion technologies.