Search Results (6)

Pulsed current has proven to be a promising alternative to direct current in electrochemical deposition, offering numerous advantages regarding deposit quality and properties. Concerning the electrodeposition of metal alloys, the role of pulsed current techniques may vary depending on the specific metals involved. We studied an innovative tin–ruthenium electroplating bath used as an anti-corrosive layer for decorative applications. The bath represents a more environmentally and economically viable alternative to nickel and palladium formulations. The samples obtained using both direct and pulsed currents were analyzed using various techniques to observe any differences in thickness, color, composition, and morphology of the deposits depending on the pulsed current waveform used for deposition. Full article

This review extensively discusses current developments in bimetallic nanoparticle–GO and bimetallic nanoparticle–MOF nanocomposites as potential catalysts for HER, along with their different synthesis methodologies, structural characteristics, and catalytic mechanisms. The photoelectrocatalytic performance of these catalysts was also compared based on parameters such as Tafel slope, current density, onset potential, turnover frequency, hydrogen yield, activation energy, stability, and durability. The review shows that the commonly used metal alloys in the bimetallic nanoparticle–GO-based catalysts for HERs include Pt-based alloys (e.g., PtNi, PtCo, PtCu, PtAu, PtSn), Pd-based alloys (e.g., PdAu, PdAg, PdPt) or other combinations, such as AuNi, AuRu, etc., while the most used electrolyte sources are H₂SO₄ and KOH. For the bimetallic nanoparticle MOF-based catalysts, Pt-based alloys (e.g., PtNi, PtCu), Pd-based alloys (e.g., PdAg, PdCu, PdCr), and Ni-based alloys (e.g., NiMo, NiTi, NiAg, NiCo) took the lead, with KOH being the most frequently used electrolyte source. Lastly, the review addresses challenges and prospects, highlighting opportunities for further optimization and technological integration of the catalysts as promising alternative photo/electrocatalysts for future hydrogen production and storage. Full article

This contribution provides an overview of platinum group elements (PGE) distribution and mineralogy in ophiolitic chromitites, which are unusually enriched in the low melting-point Rh, Pt and Pd (PPGE) compared with most chromite deposits associated with ophiolites, which are dominated by the refractory Os, Ir and Ru (IPGE). The PPGE-rich chromitites examined in this paper have a PPGE/IPGE ratio equal to or higher than 1 and represent about 7% of the ophiolitic chromitite population. These chromitites occur in the mantle unit, in the mantle-transition zone (MTZ), as well as in the supra-Moho cumulate sequence of ophiolite complexes. The age of their host ophiolites varies from Proterozoic to Eocene and, based on their composition, the chromitites can be classified into Cr-rich and Al-rich categories. Mineralogical assemblages observed in this investigation suggest that the PPGE enrichment was achieved in the magmatic stage thanks to the formation of an immiscible sulfide liquid segregating during or immediately after chromite precipitation. The sulfide liquid collected the available chalcophile PPGE that precipitated as specific phases together with Ni-Cu-Fe sulfides in the host chromitite and the silicate matrix. After their magmatic precipitation, the PPGM and associated sulfides were altered during low-temperature serpentinization and hydrothermal processes. Therefore, the original high-temperature assemblage underwent desulfurization, generating awaruite and alloys characterized by variable Pt-Pd-Rh-Cu-Ni-Fe assemblages. The occurrence of secondary PPGM containing Sb, As, Bi, Te, Sn, Hg, Pb and Au suggests that these elements might have been originally present in the differentiating magmatic sulfide liquid or, alternatively, they were introduced by an external source transported by hydrothermal and hydrous fluids during the low-temperature evolution of the host ophiolite. Although the PGE content may be as high as 81,867 ppb, as was found in one sample from Shetland chromite deposits, the ophiolitic chromitites are not presently considered as a potential resource because of the following circumstances: (1) enrichment of PPGE in podiform chromitites is a local event that occurs randomly in ophiolite sequences, (2) ore deposits are small and characterized by uneven distribution and high discontinuity, (3) physical characters of the mineralization only allow poor recovery of the precious metals mainly due to the minute grain size, and (4) for these reasons, the PPGE reserves in ophiolitic chromitites cannot compete, at the moment, with those in chromite deposits of the Bushveld type that will supply world demands for centuries using current mining techniques. Full article

Functional and robust catalyst supports are vital in the catalysis field, and the development of universal and efficient catalyst support is essential but challenging. Traditional catalyst fabrication methods include the carbonization of ordered templates and high−temperature dehydration. All these methods involve complicated meso−structural disordering and allow little control over morphology. To this end, a eutectic GaInSn alloy (EGaInSn) was proposed and employed as an intermediate to fabricate low−dimensional ordered catalyst support materials. Owing to the lower Gibbs free energy of Ga₂O₃ compared to certain types of metals (e.g., Al, Mn, Ce, etc.), we found that a skinny layer of metal oxides could be formed and exfoliated into a two−dimensional nanosheet at the interface of liquid metal (LM) and water. As such, EGaInSn was herein employed as a reaction matrix to synthesize a range of two−dimensional catalyst supports with large specific surface areas and structural stability. As a proof−of-concept, Al₂O₃ and MnO were fabricated with the assistance of LM and were used as catalyst supports for loading Ru, demonstrating enhanced structural stability and overall electrocatalytic performance in the oxygen evolution reaction. This work opens an avenue for the development of functional support materials mediated by LM, which would play a substantial role in electrocatalytic reactions and beyond. Full article

In view of a possible use as anode materials in acidic direct alcohol fuel cells, the electro-catalytic activity of Pt-Ni and Pt-M-Ni (M = Ru, Sn) catalysts for methanol and ethanol oxidation has been widely investigated. An overview of literature data regarding the effect of the addition of Ni to Pt and Pt-M on the methanol and ethanol oxidation activity in acid environment of the resulting binary and ternary Ni-containing Pt-based catalysts is presented, highlighting the effect of alloyed and non-alloyed nickel on the catalytic activity of these materials. Full article

We prepared monodisperse Pt₂Ru₃ nanoparticles supported on carbon black and Sb-doped SnO₂ (denoted as Pt₂Ru₃/CB and Pt₂Ru₃/Sb-SnO₂) with identical alloy composition and particle size distribution by the nanocapsule method. The activities for the hydrogen oxidation reaction (HOR) of these anode catalysts were examined in H₂-saturated 0.1 M HClO₄ solution in both the presence and absence of carbon monoxide by use of a channel flow electrode at 70 °C. It was found that the CO-tolerant HOR mass activity at 0.02 V versus a reversible hydrogen electrode (RHE) on the Pt₂Ru₃/Sb-SnO₂ electrode was higher than that at the Pt₂Ru₃/CB electrode in 0.1 M HClO₄ solution saturated with 1000 ppm CO (H₂-balance). The CO tolerance mechanism of these catalysts was investigated by in situ attenuated total reflection Fourier transform infrared reflection-adsorption spectroscopy (ATR-FTIRAS) in 1% CO/H₂-saturated 0.1 M HClO₄ solution at 60 °C. It was found, for the Pt₂Ru₃/Sb-SnO₂ catalyst, that the band intensity of CO linearly adsorbed (CO_L) at step/edge sites was suppressed, together with a blueshift of the CO_L peak at terrace sites. On this surface, the HOR active sites were concluded to be more available than those on the CB-supported catalyst surface. The observed changes in the adsorption states of CO can be ascribed to an electronic modification effect by the Sb-SnO₂ support. Full article