TL;DR: In this paper, the sulphur content of the deposited layers, which is dependent on the thiourea content of an electroplating bath, ranged between 10 and 20 wt%.
Abstract: Active layers for hydrogen evolution were prepared electrolytically from nickel-plating baths containing various amounts of thiourea. The sulphur content of the deposited layers, which is dependent on the thiourea content of the electroplating bath, ranged between 10 and 20 wt%. X-ray photoelectron spectroscopic (XPS) analysis revealed that sulphur was present in the layers not only in the form of sulphide, but also in the forms of thiourea and sulphate entrained from the nickel-plating bath. X-ray diffraction analysis showed that the coatings were poorly crystalline. Nickel sulphide, which produces an X-ray diffraction pattern, was present only in coatings deposited from baths with higher amounts of thiourea. The surface layers of such coatings contained a maximum of 10 at % nickel in the form of Ni3S2. When the Ni−Sx electrodes were under load in 1m KOH over a long period, the hydrogen overpotential was found to vary with time. On the basis of XPS measurements, the initial decrease in hydrogen overpotential was ascribed to the washing-out of adsorbed residues of thiourea. The subsequent increase in the overpotential was due to the deposition of iron on to the surface of the layers from the electrolyte used.
TL;DR: In this paper, a facile periodic potential reversal (PR) technique was used to supersede Pt counter electrodes (CEs) of dye-sensitized solar cells (DSCs).
Abstract: Nickel sulfides have been, for the first time, electrodeposited on transparent conductive glass by a facile periodic potential reversal (PR) technique to supersede Pt counter electrodes (CEs) of dye-sensitized solar cells (DSCs). The composition and electrochemical catalytic activity of the nickel sulfide films prepared by PR technique are different from those of the ones deposited by the commonly used potentiostatic (PS) technique. PR technique produces transparent single-component NiS, while co-deposition of Ni and NiS is found in the opaque films prepared by PS method. The nickel sulfide deposited by PR technique shows high catalytic activity for the reduction of I3− to I− in a DSC. DSC with the CE deposited by PR technique performs much better (6.82%) than that by PS method (3.22%), and is comparable to the device with conventional Pt coated CE (7.00%).
TL;DR: In this article, a hierarchically porous Ni 3 S 2 nanorod array foam was successfully prepared through a simple hydrothermal process assisted by the pretreatment with HCl. The resulting hierarchical porous nanostructures exhibits excellent catalytic activity and stability towards both HER and OER with low overpotential of 200mV and 217mV at current density of 10mA cm −2 for HER and oER, respectively, which are among the best nonnoble metal HER/OER electrocatalysts reported in literatures.
Abstract: It is highly challenging but imperative to develop highly efficient, low-cost and environmentally friendly bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, we successfully prepared hierarchically porous Ni 3 S 2 nanorod array foam through a simple hydrothermal process assisted by the pretreatment with HCl. The resulting hierarchically porous Ni 3 S 2 nanostructures exhibits excellent catalytic activity and stability towards both HER and OER with low overpotential of 200 mV and 217 mV at current density of 10 mA cm −2 for HER and OER, respectively, which are among the best non-noble metal HER/OER electrocatalysts reported in literatures. The as-prepared bifunctional electrocatalyst for both HER and OER could act as the promising electrode materials for water splitting.
TL;DR: In this article, the hydrogen evolution reaction was studied on electrolytically prepared amorphous smooth NiP(x) layers with a phosphorus content of 3 to 14 wt%.
Abstract: Hydrogen evolution reaction was studied on electrolytically prepared amorphous smooth NiP(x) layers with a phosphorus content of 3 to 14 wt%. NiP(x) electrodes with a low P content about 3 wt% are very active. At the potential E = − 0.2 V [rhe] in 1 N KOH at 23 °C the current density of the hydrogen evolution is ≈0.2 A cm−2, which is approximately 10 times higher than on platinum and 300 times higher than on nickel. The polarization curve NiP(3%) has a low slope b ≈ 0.058 V dec−1 in the range of current densities 0.001–1 A cm−2. This low slope is caused probably by a barrierless electron transfer reaction mechanism. High activity of amorphous NiP(3) electrodes is caused by the ability of these electrodes to adsorb and absorb great amounts of hydrogen, which changes the electron structure of the basic metal. The thermal treatment of layers at approximately 150 °C causes the crystallisation of layers and the loss both of the activity and the ability to sorb hydrogen.
TL;DR: In this article, a hierarchically structured multi-elements water splitting electrocatalysts consisting of Fe, Co, Ni, S, P, and O with a one-step electrodeposition method is presented.
Abstract: Economically producing hydrogen via electrocatalytic water splitting requires highly efficient and low-cost catalysts and scalable synthetic strategies. Herein, we present the preparation of hierarchically structured multi-elements water splitting electrocatalysts consisting of Fe, Co, Ni, S, P, and O with a one-step electrodeposition method. By tuning of the non-metal compositions of the catalysts, the electrochemical performances of the catalysts for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in 1 M KOH can be rationally modified, respectively. Under the optimum conditions, current densities of 100 and 1000 mA cm–2 were obtained at overpotentials of only 135 and 264 mV on the HER catalyst and 258 and 360 mV on the OER catalyst, respectively. When the best-performing HER and OER catalysts were assembled in a two-electrode system for overall water splitting, a current density of 10 mA cm–2 could be obtained under a cell voltage of 1.46 V with long-term durability. A...
TL;DR: In this article, a nickel-based electrodes were prepared using composite electrodeposition technique in a nickel sulphamate bath containing suspended micro- or nano-sized CeO2 particles.
Abstract: In this work, nickel-based electrodes were prepared using composite electrodeposition technique in a nickel sulphamate bath containing suspended micro- or nano-sized CeO2 particles. The prepared NieCeO2 composite electrodes exhibit an enhanced high catalytic activity toward hydrogen evolution reaction (HER) in alkaline solutions. X-ray diffraction patterns indicated that the CeO2 particles have been successfully incorporated into the Ni matrix and altered the texture coefficient (TC) of the Ni layer. The morphology of the obtained coatings was characterized by Scanning Electron Microscopy, and the CeO2 content was determined by coupled energy dispersive X-ray spectrometry. The thermal stability of the composite electrodes was analyzed by thermogravimetric and differential scanning calorimetry, showing a good thermal stability. The catalytic activity of the composite electrodes for HER was measured by steady-state polarization and electrochemical impedance spectroscopy techniques in 1.0 M NaOH solution at room temperature. The exchange current density of HER on the NieCeO2 composite electrodes was much higher than that on Ni electrode. EIS results suggested that a synergetic effect on HER may exist between CeO2 particles and Ni matrix. Compared to nano-CeO2, the micro-CeO2 derived composite electrodes showed higher electrochemical activity. The possible correlation among particle size, content and catalytic activity is discussed.