Multifunctional two-dimensional glassy graphene devices for vis-NIR photodetection and volatile organic compound sensing

Multifunctional devices are of great interest for integration and miniaturization on the same platform, but simple addition of functionalities would lead to excessively large devices. Here, the photodetection and chemical sensing device is developed based on two-dimensional(2D) glassygraphene that meets similar property requirements for the two functionalities. An appropriate bandgap arising from the distorted lattice structure enables glassy graphene to exhibit comparable or even improved photodetection and chemical sensing capability, compared with pristine graphene. Due to strong interactions between glassy graphene and the ambient atmosphere, the devices are less sensitive to photoinduced desorption than the ones based on graphene. Consequently,the few-layer glassy graphene device delivers positive photoresponse, with a responsivity of 0.22 A W^(-1) and specific detectivity reaching ~10^(10) Jones under 405 nm illumination.Moreover, the intrinsic defects and strain in glassy graphene can enhance the adsorption of analytes, leading to high chemical sensing performance. Specifically, the extracted signalto-noise-ratio of the glassy graphene device for detecting acetone is 48, representing more than 50% improvement over the device based on graphene. Additionally, bias-voltage-and thickness-dependent volatile organic compound(VOC) sensing features are identified, indicating the few-layer glassy graphene is more sensitive. This study successfully demonstrates the potential of glassy graphene for integrated photodetection and chemical sensing, providing a promising solution for multifunctional applications further beyond.

Thermodynamic and kinetics of hydrogen photoproduction enhancement by concentrated sunlight with CO_(2) photoreduction by heterojunction photocatalysts

For achieving water splitting into hydrogen under sunlight for practical applications,the high efficiencies of the photoreduction of CO_(2) over TiO_(2)/Fe3O4 photocatalysts combined with hydrogenation of water splitting over Pt/TiO_(2) were investigated by practical concentrated solar energy compared with Hg lamp and Xe lamp.Based on AI analysis on the influence factors,the key parameters for TOC concentration were photocatalysts,Na2CO3 concentration and radiation intensity while the key parameters for hydrogen production were photocatalysts,radiation intensity,and TOC concentration.Accordingly,the mechanism of concentrated sunlight effects has been discussed from the view of thermodynamics and kinetics.The concentrated sunlight provides a simultaneous supply of sufficient electron–hole pairs and thermal energy.Water to hydrogen and CO_(2) reduction are both enhanced in concentrated sunlight due to endothermal reactions.Doping changes the internal electric field of p-n junction of in different possible ways,and thus composite photocatalysts with favorable formation of p-n junctions would enhance the charge separation by internal electric field.Moreover,photocatalysts are beneficial for providing more excited electrons at a time for achieving CO_(2) photoreduction at the surface region of the particles with higher density of radiation by concentrated solar energy.Subsequently,products from CO_(2) photoreduction,acting as sacrificial electron donors,improved hydrogen evolution in solar-mediated water splitting for prohibiting reverse reactions.