Rationally Engineered Cu₃N/g-C3N4 Heterostructure for Multifunctional Photocatalysis, Hydrogen Evolution, and Electrochemical Sensing

Developing multifunctional catalytic materials that can operate efficiently across diverse energy and environmental applications remains a major scientific challenge. Herein, we present a rationally engineered Cu3N/g-C3N4 nanocomposite consisting of ultrafine Cu3N nanocubes uniformly anchored onto graphitic carbon nitride, synthesized via a two-step aminothermal process followed by thermal polycondensation. The intimate interfacial contact between Cu3N and g-C3N4 forms an efficient heterojunction that enhances charge separation, accelerates interfacial electron transfer, and increases the density of catalytically active sites. Under UV–visible irradiation, the Cu3N/g-C3N4 nanocomposite achieves complete degradation of Rhodamine B within 50 min, demonstrating superior photocatalytic performance attributed to suppressed electron–hole recombination and improved reactive species generation. As an electrocatalyst for the hydrogen evolution reaction (HER), the composite requires a low overpotential of 120 mV to deliver 10 mA cm-2, exhibits a favourable Tafel slope of 73 mV dec-1, and maintains excellent long-term electrochemical stability, highlighting its fast reaction kinetics and robust durability. Beyond photo- and electrocatalysis, the nanocomposite also functions as a sensitive electrochemical sensor for the detection of the anthelmintic drug mebendazole, showing a wide linear detection range (7.5 × 10-9 to 1.23 × 10-8 M), high sensitivity (29.47 μA nM-1 cm-2), and a low detection limit of 18 nM. This study establishes Cu3N/g-C3N4 as a cost-effective and structurally robust multifunctional catalytic platform, offering an integrated strategy for environmental remediation, sustainable hydrogen production, and pharmaceutical sensing.