Palladium nanowires prepared using the lithographically patterned nanowire electrodeposition (LPNE) method are used to detect hydrogen gas (H2). These palladium nanowires are prepared by electrodepositing palladium from EDTA-containing solutions under conditions favoring the formation of β-phase PdHx. The Pd nanowires produced by this procedure are characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. These nanowires have a mean grain diameter of 15 nm and are composed of pure Pd with no XPS-detectable bulk carbon. The four-point resistance of 50-100 μm segments of individual nanowires is used to detect H2 in N2 and air at concentrations ranging from 2 ppm to 10%. For low [H2] < 1%, the response amplitude increases by a factor of 2-3 with a reduction in the lateral dimensions of the nanowire. Smaller nanowires show accelerated response and recovery rates at all H2 concentrations from, 5 ppm to 10%. For 12 devices, response and recovery times are correlated with the surface area/volume ratio of the palladium detection element. We conclude that the kinetics of hydrogen adsorption limits the observed response rate seen for the nanowire, and that hydrogen desorption from the nanowire limits the observed recovery rate; proton diffusion within PdHx does not limit the rates of either of these processes.

Nitrate is ar aw ingredient for the production of fertilizer,g unpowder,a nd explosives.D eveloping an alternative approach to activate the NNbond of naturally abundant nitrogen to form nitrate under ambient conditions will be of importance.Herein, pothole-rich WO 3 was used to catalyse the activation of N Nc ovalent triple bonds for the direct nitrate synthesis at room temperature.T he pothole-rich structure endues the WO 3 nanosheet more dangling bonds and more easily excited high momentum electrons,w hicho vercome the two major bottlenecks in NNb ond activation, that is,p oor binding of N 2 to catalytic materials and the high energy involved in this reaction. The average rate of nitrate production is as high as 1.92 mg g À1 h À1 under ambient conditions,without any sacrificial agent or precious-metal co-catalysts.M ore generally,t he concepts will initiate an ew pathwayf or triggering inert catalytic reactions.

Iron pyrite (cubic FeS 2 ) is a promising candidate absorber material for earth-abundant thin-fi lm solar cells. In this report, single-phase, large-grain, and uniform polycrystalline pyrite thin fi lms are fabricated on glass and molybdenum-coated glass substrates by atmospheric-pressure chemical vapor deposition (AP-CVD) using the reaction of iron(III) acetylacetonate and tert -butyl disulfi de in argon at 300 ° C, followed by sulfur annealing at 500-550 ° C to convert marcasite impurities to pyrite. The pyrite-marcasite phase composition depends strongly on the concentration of sodium in the growth substrate and the sulfur partial pressure during annealing. Phase and elemental composition of the fi lms are characterized by X-ray diffraction, Raman spectroscopy, Auger electron spectroscopy, secondary ion mass spectrometry, Rutherford backscattering spectrometry, and X-ray photoelectron spectroscopy. The in-plane electrical properties are surprisingly insensitive to phase and elemental impurities, with all fi lms showing p -type, thermally activated transport with a small activation energy ( ≈ 30 meV), a roomtemperature resistivity of ≈ 1 Ω cm, and low mobility. These ubiquitous electrical properties may result from robust surface effects. These CVD pyrite thin fi lms are well suited to fundamental electrical studies and the fabrication of pyrite photovoltaic device stacks.

Electrocatalytic water splitting, which underpins a series of sustainable energy conversion technologies, has become even more relevant as our energy needs have increased. Exploring efficient non-precious-metal electrocatalysts is necessary for the widespread application of this energy storage model. Twodimensional (2D) ultrathin solids with a special atomic and electronic structure are full of unlimited potential in the pursuit of high-efficiency electrocatalysts and have been identified as a perfect platform for establishing clear structureproperty relationships. Hence, in this review, we first clear up the fundamental relationship between intrinsic charge and spin ordering and electrocatalytic properties. Then, on this basis, we summarize recent attempts to regulate electrical behavior and spin ordering in 2D ultrathin solids to optimize electrocatalytic water-splitting performance. In addition, we highlight the coupling relationship among lattice, charge, and spin ordering in ultrathin electrocatalysts. Finally, we also present some personal perspectives on the challenges and future research directions in this promising area.