A metal-rich form of Ni-selenide, nickel subselenide, Ni3Se2 has been investigated as a potential oxygen evolution electrocatalyst under alkaline conditions for the first time. The Ni3Se2 phase has a structure similar to the sulfur mineral heazlewoodite, which contains metal–metal bonding. The electrocatalytic activities of Ni3Se2 towards OER were seen to be at par with or even superior to the transition metal oxide based electrocatalyst in terms of onset overpotential for O2 evolution as well as overpotential to reach a current density of 10 mA cm−2 (observed at 290 mV). The electrocatalytic Ni3Se2 films were grown by electrodeposition on conducting substrates and the deposition parameters including the pH of the electrolytic bath, deposition potential, and substrate composition were seen to have some influence on the catalytic activity. So far, Ni3Se2 films deposited on the Au-coated Si substrate was seen to have the lowest overpotential. Annealing of the as-deposited electrocatalytic films in an inert atmosphere, enhanced their catalytic efficiencies by decreasing the overpotential (@10 mA cm−2) as well as increasing the current density. The structure and morphology of these films has been characterized by powder X-ray diffraction, scanning and transmission electron microscopy, Raman, and X-ray photoelectron spectroscopy. Catalytic activities were investigated through detailed electrochemical studies under alkaline conditions, including linear sweep voltammetry, chronoamperometric studies at constant potential, electrochemical surface area determination and calculation of the Tafel slope. The Faradaic efficiency of this catalyst has been estimated by reducing the evolved O2 in a RRDE set-up which also confirmed that the evolved gas was indeed O2. In addition to low overpotentials, these Ni3Se2 electrodeposited films were seen to be exceptionally stable under conditions of continuous O2 evolution for an extended period (42 h).

Nickel selenide as a high-efficiency catalyst for oxygen evolution reaction

The porous three-dimensional (3-D) flower structures assembled by numerous ultrathin flakes were favor for strengthen electromagnetic absorption capability. However, it still remains a big challenge to fabricate such kind of materials. In this study, an easy and flexible two-step method consisting of hydrothermal and subsequent annealing process have been developed to synthesize the porous 3-D flower-like Co/CoO. Interestingly, we found that the suitable heat treatment temperature played a vital role on the flower-like structure, composition, and electromagnetic absorption properties. In detail, only in the composite treated with 400 °C can we gain the porous 3-D flower structure. If the annealing temperature were heated to 300 °C, the Co element was unable to generate. Moreover, when the annealing temperature increased from 400 to 500 °C, these flower-like structures were unable to be kept because the enlarged porous diameter would wreck the flower frame. Moreover, these 3-D porous flower-like structures...

Porous Three-Dimensional Flower-like Co/CoO and Its Excellent Electromagnetic Absorption Properties

Earth-abundant, low-cost electrocatalysts with outstanding catalytic activity in the electrochemical hydrogen evolution reaction (HER) are critical in realizing the hydrogen economy to lift our future welfare and civilization. Here we report that excellent HER activity has been achieved with three-dimensional core/shell Co/Co3O4 nanosheets composed of a metallic cobalt core and an amorphous cobalt oxide shell. A benchmark HER current density of 10 mA cm(-2) has been achieved at an overpotential of ∼90 mV in 1 M KOH. The excellent activity is enabled with the unique metal/oxide core/shell structure, which allows high electrical conductivity in the core and high catalytic activity on the shell. This finding may open a door to the design and fabrication of earth-abundant, low-cost metal oxide electrocatalysts with satisfactory hydrogen evolution reaction activities.

Three-Dimensional Crystalline/Amorphous Co/Co3O4 Core/Shell Nanosheets as Efficient Electrocatalysts for the Hydrogen Evolution Reaction

Transparent electrodes attract intense attention in many technological fields, including optoelectronic devices, transparent film heaters and electromagnetic applications. New generation transparent electrodes are expected to have three main physical properties: high electrical conductivity, high transparency and mechanical flexibility. The most efficient and widely used transparent conducting material is currently indium tin oxide (ITO). However the scarcity of indium associated with ITO's lack of flexibility and the relatively high manufacturing costs have a prompted search into alternative materials. With their outstanding physical properties, metallic nanowire (MNW)-based percolating networks appear to be one of the most promising alternatives to ITO. They also have several other advantages, such as solution-based processing, and are compatible with large area deposition techniques. Estimations of cost of the technology are lower, in particular thanks to the small quantities of nanomaterials needed to reach industrial performance criteria. The present review investigates recent progress on the main applications reported for MNW networks of any sort (silver, copper, gold, core-shell nanowires) and points out some of the most impressive outcomes. Insights into processing MNW into high-performance transparent conducting thin films are also discussed according to each specific application. Finally, strategies for improving both their stability and integration into real devices are presented.

Metallic Nanowire-Based Transparent Electrodes for Next Generation Flexible Devices: a Review

The exploitation of a low-cost catalyst is desirable for hydrogen generation from electrolysis or photoelectrolysis. In this study we have demonstrated that nickel phosphide (Ni12P5) nanoparticles have efficient and stable catalytic activity for the hydrogen evolution reaction. The catalytic performance of Ni12P5 nanoparticles is favorably comparable to those of recently reported efficient nonprecious catalysts. The optimal overpotential required for 20 mA/cm(2) current density is 143 ± 3 mV in acidic solution (H2SO4, 0.5 M). The catalytic activity of Ni12P5 is likely to be correlated with the charged natures of Ni and P. Ni12P5 nanoparticles were introduced to silicon nanowires, and the power conversion efficiency of the resulting composite is larger than that of silicon nanowires decorated with platinum particles. This result demonstrates the promising application potential of metal phosphide in photoelectrochemical hydrogen generation.

Ni12P5 Nanoparticles as an Efficient Catalyst for Hydrogen Generation via Electrolysis and Photoelectrolysis

Photoelectron-spectroscopic study of nickel, manganese and cobalt selenides

High-temperature oxidation of SnSe in the temperature interval 25 to 650‡ C has been studied by X-ray photoelectron spectroscopy, X-ray diffraction and thermal analysis techniques. Exposure to dry oxygen (760 torr pressure) at up to 200‡ C leads to the formation of SnO2 on the surface. The high-temperature bulk oxidation between 250 and 650‡ C goes through distinct steps of formation of intermediate tin oxoselenides, presumably SnOSe or SnSeO2 and its subsequent conversion to SnO2.

Mechanism of high-temperature oxidation of tin selenide

Photoelectron spectroscopy study of surface oxidation of SnTe PbTe and PbSnTe

Source of instability in solid state polymeric electrochromic cells : the deterioration of indium tin oxide electrodes

It has been found possible to prepare excellent solar selective molybdenum black films by a modified catholic electrodeposition technique. These films have been characterized using XPS, AES depth profiling, SEM, chemical analysis, X-ray diffraction and VIS-IR reflectance spectroscopy. The study shows that the film is composite of MoO3 matrix containing fine nickel and copper particles. It is also observed that the copper concentration increases from the surface of the film towards the substrate. Reported solar selectivity can be explained using the Maxwell Gannett theory along with the stacked layer treatment developed by Anderson.

A.B. Mandale

Papers

Photoelectron-spectroscopic study of nickel, manganese and cobalt selenides

Mechanism of high-temperature oxidation of tin selenide

Photoelectron spectroscopy study of surface oxidation of SnTe PbTe and PbSnTe

Source of instability in solid state polymeric electrochromic cells : the deterioration of indium tin oxide electrodes

Characterization of solar selective molybdenum black films