Stabilizing metastable Cu+ species in atomically coherent WO3/CuWO4 heterojunctions for robust H2S sensing

A Cu 2+ -regulated one-step hydrothermal route simultaneously tailors the dimension and facet exposure of WO 3 nanostructures. • In-situ atomically coherent WO 3 /CuWO 4 p-n heterointerfaces stabilize Cu + as highly active oxygen-activation centers. • Cu + /Cu 2+ redox-coupled oxygen activation and H 2 S dissociation enable high response, fast kinetics, and robust selectivity. Precise control over crystal morphology and interfacial electronic structure is pivotal for advancing gas sensing performance, yet simultaneously optimizing these parameters remains a formidable challenge. Herein, we report a one-step hydrothermal strategy that orchestrates the dimensional evolution of WO 3 -based nanomaterials from high-aspect-ratio nanorods to ultrathin nanosheets by simply tuning Cu 2+ concentration. This morphological transformation is driven by a synergistic mechanism involving competitive citrate coordination and facet-selective adsorption of Cu 2+ ions. Crucially, this in-situ growth protocol constructs atomically coherent WO 3 /CuWO 4 p-n heterojunctions that uniquely stabilize a high density of metastable Cu + species. These Cu + centers act as potent electron donors, dramatically enriching surface-active superoxide radicals (O 2 − ) and lowering the activation energy for gas reactions. The optimized Cu-WO 3 -1 sensor exhibits exceptional performance toward hydrogen sulfide (H 2 S), the sensor exhibits a relatively high response (R a /R g  = 218.2 at 50 ppm, 150 °C), ultrafast response/recovery kinetics (13 s/101 s), and remarkable selectivity against interfering gases. Mechanistic studies reveal that the superior performance stems from a dual-function Cu + /Cu 2+ redox cycle: Cu + facilitates efficient H S bond dissociation and oxygen activation, while the reversible formation of conductive CuS and subsequent surface regeneration ensure rapid signal recovery. This work establishes a universal paradigm for synchronizing facet engineering with valence-state modulation to design next-generation high-performance chemiresistive sensors. Employing a one-step Cu 2+ -modulated hydrothermal strategy, we simultaneously achieved dimensional control of WO 3 -based nanostructures and constructed atomically coherent WO 3 /CuWO 4 p–n heterojunctions. This approach successfully stabilized a high density of metastable Cu + species, significantly enriched surface-active superoxide radicals (O 2 − ), and lowered the activation energy for gas reactions. The Cu-WO 3 -1 composite enabled ultrasensitive H 2 S detection, exhibiting a high response of 218.2 toward 50 ppm H₂S at 150 °C, along with rapid response (13 s) and recovery (101 s) kinetics. The outstanding performance originates from a bifunctional Cu + /Cu 2+ redox cycle: Cu + facilitates efficient H S bond cleavage and oxygen activation, while the reversible formation of conductive CuS and the subsequent surface regeneration ensure rapid signal recovery. Download: Download high-res image (259KB) Download: Download full-size image