III–VI and IV–VI van der Waals Semiconductors InSe, GaSe and GeSe: A Suitable Platform for Efficient Electrochemical Water Splitting, Photocatalysis and Chemical Sensing

Abstract

Here, we discuss the physicochemical properties of both bulk and nanosheets of III-VI and IV-VI metal chalcogenides and their application capabilities in electrocatalysis, photocatalysis, and gas sensing by combining density function theory with surface-science experiments. In particular, GaSe, InSe, and GeSe are van der Waals semiconductors stable in water media and robust against CO poisoning, which make them suitable candidates for application as low-cost (photo)catalysts in liquid media. Both bulk and exfoliated III-VI and IV-VI metal chalcogenides are prone to oxidation, with the formation of an oxide skin in oxidative environments. The self-assembled heterostructure formed by the oxide skin and the underlying bulk of metal chalcogenides makes the Heyrovsky step of HER energeti-cally favourable. Both metal and Se vacancies are necessary to decrease the energy barrier for HER in acid media. The oxidation modified the band gap, enabling the activation of photocatalytic process with different wavelengths. Moreover, the self-assembled metal-oxide/metal-chalcogenide heterostructure also enables sensing of NO 2 , NH 3 and CO for an operational temperature up to 600 °C. Thus, III-VI and IV-VI semiconductors represent a suitable platform for electrochemistry, photocatalysis, and chemical sensing, owing to their low costs as raw materials and the superior application capabilities activated just exploiting the natural interaction with air, which is beneficial for improving the (photo)electrocatalyst activity and the gas-sensing performances.

Quaternary Rare-Earth Oxyselenides RE4Ga2Se7O2 (RE = Pr, Nd) with Trigonal Bipyramidal GaSe5 Units: Evaluation of Optical, Thermoelectric, and Electrocatalytic Properties

“…73−76 However, given the XPS results, it is unlikely that it originates from involvement of a Pr 4+ /Pr 3+ couple, but perhaps through mechanisms like those in GaSe, which undergoes similar changes in its Ga 3d and Se 3d XPS spectra. 77,78…”

“…For Nd 4 Ga 2 Se 7 O 2 , the spectra were much less significantly affected, suggesting only mild surface oxidation. The superior electrocatalytic performance of the Pr member is an interesting result that appears to be observed in other RE -containing catalysts for water splitting, including perovskites and alloys. − However, given the XPS results, it is unlikely that it originates from involvement of a Pr 4+ /Pr 3+ couple, but perhaps through mechanisms like those in GaSe, which undergoes similar changes in its Ga 3d and Se 3d XPS spectra. , …”

Improved Charge Transfer for NO2 Gas Sensors by Using 0D SnS Quantum Dot/2D WSe2 Heterostructures

“…Furthermore, it has been found that introducing QDs to the surface of 2D nanomaterials increases the number of activation sites in 2D materials. As a result, most of the researchers are trying to make ultrasensitive detectors by using such heterojunctions. , There are several articles based on innovative 2D semiconductors, and their heterostructure sensor has been reported in the last few years. − The research may have used a specific research design or methodology that has limitations. For example, the research may have relied on self-report measures, which could be subject to biases or may not fully capture the complexity of the phenomenon under investigation.…”

Regioselective Friedel–Crafts Acylation Reaction Using Single Crystalline and Ultrathin Nanosheet Assembly of Scrutinyite-SnO2

“… 1 − 15 These compelling physical/chemical properties of 2D nanomaterials compared to bulk counterparts improve their applicability in various fields of catalysis, nanomechanics, gas sensors, and so on. 2 − 20 Particularly, the ultrathin nanosheets are most versatile one as nearly all the active atoms of the material lie at the surface of nanosheets maximizing the utility of such atoms. 2 − 25 Hence, the interaction between the weakly coordinated active surface atoms of the nanosheets and reactant species and the distinctive electronic property arising from 2D effects of nanosheets can tremendously change the activity of ultrathin nanosheets compared to conventional nanosheets/nanostructures.…”

“…Ultrathin two-dimensional (2D) nanomaterials are a class of material endowed with sheetlike nanostructure of atomic thicknesses and high area/thickness aspect ratios. − Owing to the geometric confinement in one of the dimensions, they have been attracting a lot of attention as a new generation advanced material with distinctive physical/chemical properties. − These compelling physical/chemical properties of 2D nanomaterials compared to bulk counterparts improve their applicability in various fields of catalysis, nanomechanics, gas sensors, and so on. − Particularly, the ultrathin nanosheets are most versatile one as nearly all the active atoms of the material lie at the surface of nanosheets maximizing the utility of such atoms. − Hence, the interaction between the weakly coordinated active surface atoms of the nanosheets and reactant species and the distinctive electronic property arising from 2D effects of nanosheets can tremendously change the activity of ultrathin nanosheets compared to conventional nanosheets/nanostructures. − The synthesis of ultrathin nanosheets from 2D graphene and graphene-type materials with layered structures that are bonded by weak van der Waals force are easy to prepare from their bulk structure. − However, achieving ultrathin nanosheets and their assembly of a s...…”