RESUMEN
Metal oxide semiconductor (MOS) thin films are of critical importance to both fundamental research and practical applications of gas sensors. Herein, a high-performance H2 sensor based on palladium (Pd) and rhodium (Rh) co-functionalized Fe2 O3 films with an ultrathin thickness of 8.9 nm deposited by using atomic layer deposition is reported. The sensor delivers an exceptional response of 105.9 toward 10 ppm H2 at 230 °C, as well as high selectivity, immunity to humidity, and low detection limit (43 ppb), which are superior to the reported MOS sensors. Importantly, the Fe2 O3 film sensor under dynamic H2 detection is for the first time observed by operando transmission electron microscopy, which provides deterministic evidence for structure evolution of MOS during sensing reactions. To further reveal the sensing mechanism, density functional theory calculations are performed to elucidate the sensitization effect of PdRh catalysts. Mechanistic studies suggest that Pd promotes the adsorption and dissociation of H2 to generate PdHx , while Rh promotes the dissociation of oxygen adsorbed on the surface, thereby jointly promoting the redox reactions on the films. A wireless H2 detection system is also successfully demonstrated using the thin film sensors, certifying a great potential of the strategy to practical sensors.
RESUMEN
Single-atom catalysts (SACs) hold great promise in highly sensitive and selective gas sensors due to their ultrahigh atomic efficiency and excellent catalytic activity. However, due to the extremely high surface energy of SACs, it is still a huge challenge to synthesize a stable single-atom metal on sensitive materials. Here, we report an atomic layer deposition (ALD) strategy for the elaborate synthesis of single-atom Pt on oxygen vacancy-rich Fe2O3 nanosheets (Pt-Fe2O3-Vo), which displayed ultrafast and sensitive detection to H2, achieving the stability of Pt single atoms. Gas-sensing investigation showed that the Pt-Fe2O3-Vo materials enabled a significantly enhanced response of 26.5-50 ppm of H2, which was 17-fold higher than that of pure Fe2O3, as well as ultrafast response time (2 s), extremely low detection limit (86 ppb), and improved stability. The experimental and density functional theory (DFT) studies revealed that the abundant oxygen vacancy sites of Fe2O3 contributed to stabilizing the Pt atoms via electron transfer. In addition, the stabilized Pt atoms also greatly promote the electron transfer of H2 molecules to Fe2O3, thereby achieving an excellent H2 sensing performance. This work provides a potential strategy for the development of highly selective and stable chemical sensors.