Nanoarchitectonics of carbon nitride/NiO/Zn3N2 heterointerfaces for bifunctional applications in electrocatalytic water splitting and coin cell supercapacitors

Abstract

The advancement of effective and durable electrocatalysts for water splitting and high-performance supercapacitors is essential for sustainable energy conversion and storage. Integrating transition metal heteroatoms can be a pivotal technique to fabricate nanostructures for such bifunctional applications. In this regard, we report graphitic carbon nitride/NiO/Zn₃N₂ heterointerfaces through a single-step pyrolysis method for the oxygen evolution reaction (OER) and coin cell supercapacitor devices. The synergetic interaction between NiO and Zn₃N₂ advances charge transfer kinetics and augments the electronic structure, while g-C₃N₄ provides a conductive network and additional active sites. Optimized sample NZN400 showed exceptional OER performance with a low overpotential value of 350 mV at 50 mA cm⁻², besides a low Tafel slope and high turnover frequency value. In addition, NZN400 electrodes showed a high specific capacitance value of 124 mF cm⁻² at 2 mA cm⁻² for the half-cell and 19.92 mF cm⁻² at 0.2 mA cm⁻² for the coin cell device. The fabricated device exhibited excellent cycling stability over 10 000 GCD cycles with a capacitance retention of 95.7% and coulombic efficiency of 99.4% at 0.4 mA cm⁻² and was able to power up several commercial LEDs, a digital hygrometer, and a digital stopwatch for prolonged durations. The results highlight an effective approach for integrating transition metal oxide/nitride-based compounds with carbon-based materials, aimed at developing economical and high-performance nanostructured materials for electrochemical energy applications.