Synthesis and characterization of nickel boride nanoparticles for energy conversion catalyst materials – the effect of annealing temperature

In the recent technology development, fuel cell has been widely used in many applications, including transportation and industry. Platinum catalysts are used to catalyst the reaction at the oxygen electrode, but they are expensive and has limited supply. A nickel-boron nanoparticle catalyst is proposed as a substitute for fuel cell catalyst material. The objectives are to evaluate the effect of the annealing process and to determine the characteristics of the annealed nanoparticles using scanning electron microscopy - energy dispersive X-ray (SEM-EDS), inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis, total organic carbon (TOC) analysis and X-ray diffraction (XRD). A wet chemical method was used to synthesize nickel-boron nanoparticles by chemical reduction (co-reduction) of nickel chloride and sodium borohydride. As-synthesized nickel-boron nanoparticles were annealed at temperatures of 200, 300, 400, 500, and 700 °C in an argon atmosphere for 2 h. From the experimental results, nickel-boron nanoparticles annealed at 300 °C with equal dispersion of crystalline Ni and crystalline Ni3B showed the highest catalyst performance. The yield of nickel-boron nanoparticles sized 1.1364 nm was smaller than in the literature (37 nm). The size of Ni-B nanoparticles was calculated by using the Scherrer equation with the values of full width half maximum (FWHM) obtained by peak fitting following the Gaussian model. Smaller Ni-B nanoparticles have a higher surface-area-to-volume ratio, which increases the exposure of the active sites (crystalline Ni and crystalline Ni3B phase) to the reactants (methanol) and improves catalytic activity

Corrosion behavior of Cu-Al-Ni-xCo shape memory alloys coupled with low-carbon steel for civil engineering applications

Due to the promising mechanical properties of Cu-based shape memory alloys (SMAs), their applications have become essential in many applications. In the present study, the galvanic behaviors of coupled and uncoupled steel bars with Cu–Al–Ni–xCo shape memory alloys were investigated in 3.5% NaCl solution. Thirteen measurement cells were considered for coupled and uncoupled steels and aged/unaged Cu–Al–Ni–xCo shape memory alloys. The electrochemical measurements were carried out three times to ensure the consistency of the corrosion behavior after the samples were immersed in 3.5% NaCl solution. The results revealed that the addition of 1 wt% Cobalt followed by an aging treatment led to an improvement in the corrosion resistance of coupled steel/Cu–Al–Ni–xCo shape memory alloys and a reduction in the corrosion rate by 50% for the steel bars

A Review of Transition Metal Sulfides as Counter Electrodes for Dye-Sensitized and Quantum Dot-Sensitized Solar Cells

Third-generation solar cells, including dye-sensitized solar cells (DSSCs) and quantum dot-sensitized solar cells (QDSSCs), have been associated with low-cost material requirements, simple fabrication processes, and mechanical robustness. Hence, counter electrodes (CEs) are a critical component for the functionality of these solar cells. Although platinum (Pt)-based CEs have been dominant in CE fabrication, they are costly and have limited market availability. Therefore, it is important to find alternative materials to overcome these issues. Transition metal chalcogenides (TMCs) and transition metal dichalcogenides (TMDs) have demonstrated capabilities as a more cost-effective alternative to Pt materials. This advantage has been attributed to their strong electrocatalytic activity, excellent thermal stability, tunability of bandgap energies, and variable crystalline morphologies. In this study, a comprehensive review of the major components and working principles of the DSSC and QDSSC are presented. In developing CEs for DSSCs and QDSSCs, various TMS materials synthesized through several techniques are thoroughly reviewed. The performance efficiencies of DSSCs and QDSSCs resulting from TMS-based CEs are subjected to in-depth comparative analysis with Pt-based CEs. Thus, the power conversion efficiency (PCE), fill factor (FF), short circuit current density (Jsc) and open circuit voltage (Voc) are investigated. Based on this review, the PCEs for DSSCs and QDSSCs are found to range from 5.37 to 9.80% (I−/I3− redox couple electrolyte) and 1.62 to 6.70% (S−2/Sx− electrolyte). This review seeks to navigate the future direction of TMS-based CEs towards the performance efficiency improvement of DSSCs and QDSSCs in the most cost-effective and environmentally friendly manner

Active faceted nanoporous ruthenium for electrocatalytic hydrogen evolution

Nanoporous ruthenium (np-Ru) comprising reaction active facets is synthesized from a ruthenium–cerium (Ru2Ce) alloy precursor. Spontaneous nanophase separation of Ru2Ce in an oxidative atmosphere results in a lamellar nanocomposite consisting of Ru metal and cerium oxide (CeO2). Selective leaching of the Ru–CeO2\ua0nanocomposite in sulfuric acid yields np-Ru with a high surface area of 48 m2\ua0g−1, predominantly surrounded by reaction active {100} facets. Active-faceted np-Ru efficiently catalyzed the hydrogen evolution reaction (HER) in acidic media at an overpotential of +74 mV\ua0vs.\ua0the reversible hydrogen electrode, which is 20 mV lower than that for carbon-supported Ru (Ru/C) and rather close to +58 mV for state-of-the-art Pt/C. Np–Ru has great potential in broad applications such as hydrogen battery electrodes because of its low HER overpotential and scalable synthetic protocol