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In this work, the hydrothermally synthesized SnS 2 nanosheets were calcined to form SnO 2 nanoparticle decorated SnS 2 nanosheets. The formed "raisin cake" SnS 2 /SnO 2 complex increases the specific surface area and provides more contact area for gas molecule adsorption. The SnS 2 /SnO 2 nanocomposite has a high sensing response to 50 ppm NH 3 (392) and an excellent response/recovery time (6/8 s) to 50 ppm at room temperature. Therefore, SnS 2 /SnO 2 nanocomposite has excellent repeatability, excellent NH 3 gas selectivity, and humidity stability. And it is discussed that the reason for the enhanced NH 3 sensing mechanism is the synergistic effect of SnS 2 /SnO 2 structures. The existence of heterojunction was proved by XPS. These results demonstrate that the sensing material can effectively detect NH 3 gas. • 2D SnS 2 / SnO 2 material is prepared to solve the SnO 2 agglomeration problem. • SnS 2 /SnO 2 showed rapid response and recovery times and excellent selectivity. • SnS 2 /SnO 2 sensors have potential applications in the NH3 gas-sensing field. • The formation of the SnS 2 /SnO 2 heterojunction was demonstrated by XPS. [ABSTRACT FROM AUTHOR]

[Display omitted] • Design and synthesis of (100) facet exposed SnS 2 /SnO 2 heterostructures. • Efficient hydrogen production on the (100) facet. • Experimental and theoretical clarification of boosted hydrogen generation. Tin disulfide (SnS 2), one transition metal dichalcogenide (TMD) is a cost-effective and promising electrocatalyst for hydrogen evolution reactions (HER) in the alkaline electrolytes. Its electrocatalytic HER performance is unfortunately limited, originating from its un-conspicuous inherent catalytic activities and non-favorable adsorption sites for hydrogen. Herein, a tin disulfide/stannic oxide (SnS 2 /SnO 2) heterostructure is designed and grown on the nickel foam (denoted as SnS 2 /SnO 2 -NF). The SnS 2 /SnO 2 heterostructure introduces more active (100) facets or a high density of active sites, accelerates the diffusion kinetic of electrons and ions, lowers the water dissociation energies, and optimizes adsorption energies of hydrogen atoms. On this catalyst, superior HER performance is realized in an alkaline medium. An overpotential of 108 mV at a current density of −10 mA cm–2 with a Tafel slope of 50.1 mV dec–1 and long-term durability are achieved for HER in 1 M KOH. This work paves a new way to design high-performance HER electrocatalyst through facet engineering of the designed heterostructures. [ABSTRACT FROM AUTHOR]