A room-temperature methane sensor based on Pd-decorated ZnO/rGO hybrids enhanced by visible light photocatalysis

The development of metal oxide based high-performance methane (CH4) sensors working at room temperature remains a challenge. In this work, we present a novel visible light photocatalysis-enhanced sensor based on Pd nanoparticle-decorated ZnO/rGO hybrids, enabling high-performance detection of CH4 at room temperature under visible-light illumination. A systematical comparison study indicated that the sensor based on the ternary hybrids exhibited highest p-type responses and fastest response/recovery rates to CH4 at room temperature under 470 nm visible light illumination. The sensor responses varied from 6.3% to 63.4% toward CH4 concentrations of 25 ppm to 1%, and the response and recovery time at 1% CH4 were 74 and 78 s, respectively. Moreover, the sensor exhibited full reversibility, low detection limit, long-term stability as well as excellent selectivity at room temperature. Photocatalytic measurements revealed that the CH4 sensing performances of the hybrids could be well-correlated with their photocatalytic CH4 oxidation activities under visible-light illumination. The superior room temperature CH4 sensing performance of the ternary hybrids under visible light illumination was then attributed to the synergetic effects of visible light-active Pd nanoparticles as the catalytic promoter, the efficient charge transfer rendered by rGO nanosheets as well as the multiple heterojunctions formed within the hybrids. The presently developed ternary hybrid design and the visible light photocatalysis-enhancement strategy open facile pathways to the fabrication of high-performance CH4 sensors working at room temperature.