Table 1.

Summary on comparision of metal-doped ZnO with several synthetic methods for H₂ sensing.

Authors	Method	Doping level	Range (H2)	Sensitivity
Xu et al. [6]	Chemical precipitation	0.5 wt% Pt	0.2% in air	2 at 330 °C
		0.5 wt% Ru	0.2% in air	6 at 230 °C and 2 at 400 °C
		0.5 wt% Rh	0.2% in air	115 at 300 °C
		0.5 wt% Ag	0.2% in air	9 at 400 °C
Rout et al. [8]	ZnO nanowires and ZnO nanotubes by electrochemical deposition	0 at.% Pt	1,000 ppm in air	43 at 150 °C
			1,000 ppm in air
		1 at.% Pt	1,000 ppm in air	825 at 150 °C
			1,000 ppm in air
		0 at.% Pt		18 at 150 °C
		1 at.% Pt		740 at 150 °C
Wang et al. [9]	ZnO nanorods deposited by Molecular Beam Epitaxy (MBE)	Pt-coated	500 ppm in N2	Relative response of up to 8% H2 at room temp.
Tien et al. [10]	ZnO nanorods / thin films deposited by Molecular Beam Epitaxy (MBE)	Pt-coated	500 ppm in N2	Response of Pt-coated nanorods was 3 times of thin films as prepared ZnO
Phanichphant et al. [this work]	Flame spray pyrolysis	0 at.%	1% (10,000 ppm in air)	0.2 at.%Pt showed the highest sensitivity of 164 at 350 °C
		0.2 at.%
		1 at.%
		2 at.%		0.2 at.%Pt showed the highest sensitivity of 8.2 at 350 °C
			0.1% (1,000 ppm in air)