A multifunctional Ag/WO3@g-C3N4 ternary heterostructure for environmental sensing and green hydrogen production

A ternary Ag/WO 3 @g-C 3 N 4 nanocomposite was synthesized via a hydrothermal-assisted route to enhance photocatalytic, electrocatalytic, and sensing performance. Structural and morphological characterization confirmed the coexistence of g-C 3 N 4 , monoclinic WO 3 , and face-centered cubic Ag phases with uniform nanoparticle distribution. Photoluminescence analysis revealed suppressed electron-hole recombination, indicating efficient charge separation. The composite achieved 80 % degradation of methyl orange (MO) within 30 min under visible light, outperforming bare WO 3 (70 %). In hydrogen evolution reaction (HER) studies, Ag/WO 3 @g-C 3 N 4 exhibited a low onset potential of −0.12 V vs. SCE and a Tafel slope of 46.3 mV/dec, confirming improved charge transfer kinetics. Humidity sensing measurements demonstrated a significant impedance decrease from 4.0 × 10 7 Ω to 1.0 × 10 7 Ω between 70 and 85 % RH with excellent reversibility and low hysteresis at 100 Hz. These results establish Ag/WO 3 @g-C 3 N 4 as a multifunctional heterostructure capable of synergistically integrating photocatalytic pollutant degradation, sustainable hydrogen generation, and humidity sensing for environmental and energy applications. • A ternary Ag/WO 3 @g-C 3 N 4 nanocomposite was successfully synthesized through a hydrothermal-sonication-assisted route. • Photoluminescence (PL) spectra showed a strong reduction in emission intensity and a red shift from 434 nm to 443 nm, confirming suppressed electron-hole recombination and improved charge separation. • The composite achieved 80 % methyl orange (MO) degradation within 30 min under visible light, compared to 70 % for bare WO 3 , confirming its superior photocatalytic efficiency. • Demonstrated excellent humidity sensing response with broad impedance variation from 7 to 94 % RH, low hysteresis (<2 %), and stable reversibility at 100 Hz operation frequency. • Exhibited enhanced HER performance, with a low onset potential of −0.12 V vs SCE (equivalent to −0.36 V vs RHE) and a Tafel slope of 46.3 mV dec −1 , indicating efficient charge transfer kinetics.