Ascorbic-acid-assisted hydrothermal synthesis of Pd-decorated WSe2 nanoflowers for high-performance NO2 gas sensing

Green hydrothermal synthesis of flower-like WSe 2 using biodegradable ascorbic acid as the reducing agent. • Vacuum sintering at 450 ∘ ${}^{\circ }$ C improved the crystallinity, surface activity, and charge transport of WSe 2 enhancing NO 2 sensing. • Optimal 3% Pd decoration enabled catalytic/interfacial sensitization, achieving a response of 2.26 toward 16 ppm NO 2 with good selectivity and stability. Although WSe 2 has shown great potential for NO 2 sensing, its development remains challenging because conventional hydrothermal synthesis often relies on hazardous reducing agents such as NaBH 4 and N 2 H 4 ⋅ ${}_4\cdot$ H 2 O, which may cause rapid H 2 release, toxicity, and environmentally harmful byproducts. In addition, the sensing performance of WSe 2 is often limited by insufficient active sites and inefficient charge transfer. Herein, flower-like WSe 2 nanostructures were synthesized via a one-step hydrothermal route using benign, biodegradable, eco-friendly, and cost-effective C 6 H 8 O 6 as the reducing agent. The obtained WSe 2 was vacuum-sintered at the optimized temperature of 450 ∘ ${}^{\circ }$ C and further decorated with Pd nanoparticles to enhance NO 2 sensing performance. The optimized 3% Pd-WSe 2 -450 ∘ ${}^{\circ }$ C sensor exhibited a response ( R a / R g $R_a/R_g$ ) of 2.26 toward 16 ppm NO 2 at an operating temperature of 114 ∘ ${}^{\circ }$ C, with response and recovery times of 20 and 190 s, respectively. The enhanced sensing performance is attributed to the synergistic effects of Pd decoration, improved crystallinity, abundant surface oxygen species, and efficient interfacial charge modulation. This work demonstrates a Pd-modified WSe 2 -based NO 2 gas sensor, where green synthesis, vacuum sintering, and interfacial Pd engineering synergistically enhance the sensing performance. Download: Download high-res image (368KB) Download: Download full-size image