Facile Construction of NiO–TiO2/g-C3N4 Heterostructures for High-Performance Oxygen Evolution Electrocatalysis

Abstract

The development of highly active and durable electrocatalysts for the oxygen evolution reaction (OER) is crucial for efficient hydrogen production via alkaline water splitting. However, the sluggish OER kinetics and limited activity of single-component catalysts necessitate the design of heterostructured materials with enhanced active sites, improved charge transfer, and long-term stability. In this work, NiO–TiO₂/g-C₃N₄ heterostructures were successfully synthesized and evaluated as advanced OER electrocatalysts. NiO–TiO₂ composites were initially prepared using a sol–gel method and subsequently integrated onto g-C₃N₄ nanosheets to form a heterostructure catalyst. The synthesized materials were comprehensively characterized using structural, morphological, compositional, optical, and electrochemical techniques. For electrochemical evaluation, 7 µL of catalyst suspension (1 mg mL⁻¹) was drop-cast onto a glassy carbon electrode. Using linear sweep voltammetry (LSV) technique, NiO–TiO₂/g-C₃N₄/GCE exhibited higher OER performance compared with g-C₃N₄/GCE, TiO₂/g-C₃N₄/GCE, RuO₂/GCE and NiO/g-C₃N₄/GCE, delivering an ultralow overpotential of 101 ± 1 mV versus reversible hydrogen electrode at 10 mA cm⁻² and a Tafel slope of 40 mV dec⁻¹. This enhancement is attributed to the synergistic coupling of NiO, TiO₂, and g-C₃N₄, which increases the specific surface area, exposes abundant active sites, enhances electrochemical conductivity, lowers charge–transfer resistance, and promotes rapid interfacial electron transfer, thereby accelerating OER performance. Furthermore, the catalyst demonstrated good durability after 2000 cycles and 12 h of operation, while post-OER Raman analysis revealed no obvious changes in the characteristic vibrational bands, confirming the structural stability of the heterostructure.