Fig. 3.

High response and selectivity of a Cu–ZnO NW PENG as a self-powered/active H₂S sensor. a Schematic of a Cu–ZnO NW PENG as a self-powered/active H₂S sensor. b SEM image of 5 at% Cu–ZnO NWs in top view. c HRTEM image and the SAED pattern of the edge region of a 5 at% Cu–ZnO NW. d Working mechanism of Cu–ZnO NW PENG as a self-powered/active H₂S sensor. e A continuous responding-recovering process of the device against 500 ppm H₂S. f Piezoelectric output voltage of the device under compressive force at room temperature in dry air and various concentrations of H₂S. Figures adapted from [66]