Sonochemically derived ZnO/MoS2/N-CNT heterostructures for photoelectrocatalytic oxygen evolution under neutral conditions

The development of efficient ternary heterostructures combining metal oxides, transition metal dichalcogenides, and conductive carbon nanomaterials has emerged as a promising strategy for photoelectrochemical water splitting, a key technology for green hydrogen production. However, the oxygen evolution reaction (OER) remains the main bottleneck of this process due to its sluggish kinetics. In this work, we present a facile synthesis of ternary ZnO/MoS 2 /N-CNTs heterostructures as active OER photoelectrocatalysts. MoS 2 /N-CNTs hybrids were prepared using an impinging jet reactor, a simple and scalable continuous method, while ZnO nanoparticles were obtained via microwave-assisted solvothermal synthesis. Two deposition strategies for ZnO on the MoS₂/N-CNTs surface were investigated: (I) sonochemical integration of pre-synthesized ZnO, and (II) direct deposition in a microwave reactor. To evaluate the properties of the obtained materials, a thorough analysis was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis spectrometry, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). These results, combined with comprehensive photoelectrochemical testing, allowed the most effective synthesis route to be identified. Importantly, the ternary ZnO/MoS 2 /N-CNTs material outperforms all three binary reference systems (ZnO/N-CNTs, ZnO/MoS 2 , and MoS 2 /N-CNTs), confirming a synergistic effect arising from the controlled assembly of the three components. The findings show that the sonochemical approach yields the most active photoelectrocatalysts, achieving a low onset potential of 0.178 V vs. reversible hydrogen electrode (RHE), a photocurrent of 0.465 mA·cm - 2 at 0.622 V vs. RHE, and a photovoltage of 0.402 V under open-circuit potential (OCP) conditions.