Abstract
In this study, hydrogen (H2) and methane (CH4) were used as reactive gases, and chemical vapor deposition (CVD) was used to grow single-layer graphene on a copper foil substrate. The single-layer graphene obtained was transferred to a single-crystal silicon substrate by PMMA transfer technology for the subsequent growth of nano zinc oxide. The characteristics of CVD-deposited graphene were analyzed by a Raman spectrometer, an optical microscope, a four-point probe, and an ultraviolet/visible spectrometer. The sol–gel method was applied to prepare the zinc oxide seed layer film with the spin-coating method, with methanol, zinc acetate, and sodium hydroxide as the precursors for growing ZnO nanostructures. On top of the ZnO seed layer, a one-dimensional zinc oxide nanostructure was grown by a hydrothermal method at 95 °C, using a zinc nitrate and hexamethylenetetramine mixture solution. The characteristics of the nano zinc oxide were analyzed by scanning electron microscope(SEM),x-ray diffractometer(XRD), and Raman spectrometer. The obtained graphene/zinc oxide nano-heterostructure sensor has a sensitivity of 1.06 at a sensing temperature of 205 °C and a concentration of hydrogen as low as 5 ppm, with excellent sensing repeatability. The main reason for this is that the zinc oxide nanostructure has a large specific surface area, and many oxygen vacancy defects exist on its surface. In addition, the P–N heterojunction formed between the n-type zinc oxide and the p-type graphene also contributes to hydrogen sensing.
Highlights
IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
The graphene was prepared by chemical vapor deposition, and it was grown on a copper foil substrate at a flow ratio of 1:2 of hydrogen to methane at 950 ◦ C
Graphene was grown on copper foil by chemical vapor deposition
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Due to the improvement of industrial safety awareness, the detection of flammable gases has attracted more and more attention. H2 is considered a new type of high-efficiency, clean, and inexhaustible energy source. As long as its volume ratio in the air is between 4% and 75%, it burns due to its low ignition energy and large flame propagation speed [1]. Because the storage of H2 gas is quite dangerous, in order to reduce the risk of use, the development of a high-sensitivity H2 sensor is important. If H2 is to be one of the options for renewable energy, the development of low-cost and high-sensitivity H2 sensors is crucial
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