Rational design of defect-engineered NiWO4 micro-flowers for chemiresistive gas detection: Synthesis, performance, and mechanistic understanding

The simultaneous optimization of sensitivity and humidity tolerance in metal oxide semiconductor (MOS)-based gas sensors remains a critical challenge for practical volatile compound (VOC) detection. This work demonstrates a defect engineering strategy to modulate the electronic and surface properties of NiWO 4 microstructures through controlled hydrogen reduction. Systematic annealing protocols induced a high density of oxygen vacancy (O V ) via selective oxygen removal, as confirmed by structural and spectroscopic characterization. The engineered oxygen vacancies exhibited dual functionality: (1) enhanced bulk electron transport through improved conductivity and (2) boosted surface reactivity via optimized adsorption sites. The optimized NiWO 4 sensor achieved exceptional performance for 1-octen-3-ol detection at 40 ppm, including a high response value (R a /R g  = 20.6), fast response time (22 s), and remarkable relative humidity resilience (19.7 % response drift across 20–80 % RH). The mechanism underlying enhanced sensing performance is elucidated through an oxygen adsorption model and molecular dynamics (MD) simulation. This study establishes hydrogen reduction as an effective approach for developing durable NiWO 4 sensors with combined high sensitivity and environmental stability, advancing their applicability in real-world atmospheric monitoring systems.