Interfacial synergy in NiO-MnO2-g-C3N4 ternary heterostructure nanostructure for enhanced electrocatalytic water splitting

Developing affordable, highly stable, and efficient bifunctional electrocatalysts for overall water splitting and hydrogen production is essential for advancing clean and sustainable energy technologies. In this study, a ternary heterostructure nanocomposite consisting of NiO, MnO 2 , and graphitic carbon nitride (g-C 3 N 4 ) was successfully synthesized via an ultrasound-assisted hydrothermal approach. The formation of the ternary heterostructure was confirmed through comprehensive physicochemical characterization. Among the investigated electrocatalysts, the NiO-MnO 2 -g-C 3 N 4 composite exhibited the lowest operating potential of 1.80 V vs. RHE at a current density of 10 mA cm⁻ 2 , compared with pristine NiO (1.85 V), MnO 2 (1.86 V), and g-C 3 N 4 (1.87 V), as determined from linear sweep voltammetry measurements. For the OER, the measured potential of 1.80 V vs. RHE corresponds to an overpotential of 0.57 V (570 mV), calculated using η = E-1.23V. In addition, the composite demonstrated excellent electrochemical stability, maintaining a nearly constant operating potential during prolonged operation. The enhanced electrocatalytic activity was attributed to the synergistic coupling among the three components, which increased the density of electrochemically active sites, enlarged the electrochemically active surface area, and facilitated faster interfacial charge-transfer kinetics. These findings provide valuable insights into the rational design of multifunctional ternary heterostructures and highlight the potential of earth-abundant materials as efficient electrocatalysts for sustainable water splitting.