. 2017 May 6;9(4):45. doi: 10.1007/s40820-017-0146-4

Table 1.

A summary of various NG-based self-powered gas sensors

Type	Materials	Morphology	Gas	Concentration	Sensitivity	References
Piezo	ZnO	NW	H₂S	100 ppm	13.1^A	[59]
Piezo	ZnO	NS	Humidity	10 ppm	2.96^A	[60]
Piezo	ZnO + UV	NW	Ethanol	700 ppm	85^A	[103]
Piezo	Cu/ZnO	NW	H₂S	1000 ppm	1045.76^B	[66]
Piezo	Pd/ZnO	Nanoarray	Ethanol	800 ppm	108^B	[67]
Piezo	Au/ZnO	NW Array	Ethanol	1200 ppm	72.1^A	[68]
Piezo	Cd/ZnO	NW	Humidity	70% RH	85.7^A	[70]
Piezo	Pt/ZnO	Nanoarray	Ethanol	1000 ppm	37.14^B	[69]
Piezo	SnO₂/ZnO	Nanoarray	H₂	800 ppm	471.4^B	[104]
Piezo	ZnSnO₃/ZnO	NW	Liquefied petroleum	8000 ppm	83.23^A	[105]
Piezo	α-Fe₂O₃/ZnO	NW Array	Ethanol	700 ppm	706.8^B	[106]
Piezo	NiO/ZnO	NW	H₂S	1000 ppm	84.3^B	[107]
Piezo	In₂O₃/ZnO	Nanoarray	H₂S	700 ppm	925^B	[108]
Piezo	CuO/ZnO	Nanoarray	H₂S	800 ppm	629.8^B	[71]
Piezo	CeO₂/ZnO	Nanoarray	Humidity	95% RH	82.1^A	[109]
Piezo	p-Si/n-ZnO	NR	NO₂	750 ppb(amine) 750 ppb(thiol)	23.5(amine)^A 12.8(thiol)^A	[72]
Piezo	CdS	NR	H₂S	600 ppm	62.5^A	[73]
Tribo	NiO-ZnO PDMS	NW Film	Ethanol	0.1%	37.5^A	[96]
Tribo	Pd/ZnO PDMS	NW Film	H₂	10,000 ppm	373^B	[97]
Tribo	PANI PTFE	Film Film	Ethanol	210 ppm	66.8^C	[98]
Tribo	PEDOT:PSS Ag-ZnO/nylon	Film Fiber film	C₂H₂	1000 ppm	70.9 (indoor)^A 89 (outdoor)^A	[99]
Tribo	Pd-ITO PET	Film film	H₂	1%	75^A	[93]
Tribo	Pd/ZnO PDMS	NW Film	H₂	3 vol%	1457.69^B	[94]
Tribo	Co₃O₄ Cu and PTFE	NR Film	Ethanol	100 ppm	34^D	[102]

A: S % = (V _a − V _g)/V _a × 100%; B: S % = (V _a − V _g)/V _g × 100%; C: S % = (I _a − I _g)/I _a × 100%; D: S = V _a/V _g, where V _a and V _g are the output voltages of the device under the same conditions in dry air and the test gas, respectively; I _a and I _g represent the output current in air and test gas, respectively