Insight towards Nucleation Mechanism and Change in Morphology for Nanostructured Platinum Thin Film Directly Grown on Carbon Substrate via Electrochemical Deposition

Room Temperature Electrochemical-Shock Synthesis of Solid-Solution Medium-Entropy Alloy Nanoparticles for Hydrogen Evolution

For millennia, humankind has discovered great benefits in alloying materials. Over the past 100 years, a renaissance in nanoscience has cemented the importance of nanoparticles in a variety of fields ranging from energy storage and conversion to cell biology. While many synthetic strategies exist for nanoparticle and alloy nanoparticle formation, new methods are necessary to create nanoparticles under unprecedented conditions. Here, we demonstrate a simple technique to electrodeposit solid-solution alloy nanoparticles at room temperature. When metal salts of platinum, gold, and palladium are confined to nanodroplets suspended in oil, and then a nanodroplet collides with a sufficiently negative-biased electrode to reduce the metal salts at the mass-transfer limitation, solid-solution alloy nanoparticles form. High-angle annular dark-field scanning transmission electron microscopy and single atom energy dispersive X-ray spectroscopy confirm the solid-solution microstructure of the nanoparticles. The results also confirm the nanodroplet's ability to tune alloy microstructures from amorphous to solid-solution. We further extend our technique by adding salts of silver, which lead to the synthesis of polycrystalline medium-entropy alloys. Finally, we go on to show the application of our midentropy alloys toward renewable and clean energy devices by highlighting their electrocatalytic activity toward hydrogen evolution reaction. Our method is unrivaled in its simplicity and will find applications across various fields of study.

Anion Exchange Membranes for Alkaline Polymer Electrolyte Fuel Cells-A Concise Review

Solid anion exchange membrane (AEM) electrolytes are an essential commodity considering their importance as separators in alkaline polymer electrolyte fuel cells (APEFC). Mechanical and thermal stability are distinguished by polymer matrix characteristics, whereas anion exchange capacity, transport number, and conductivities are governed by the anionic group. The physico-chemical stability is regulated mostly by the polymer matrix and, to a lesser extent, the cationic head framework. The quaternary ammonium (QA), phosphonium, guanidinium, benzimidazolium, pyrrolidinium, and spirocyclic cation-based AEMs are widely studied in the literature. In addition, ion solvating blends, hybrids, and interpenetrating networks still hold prominence in terms of membrane stability. To realize and enhance the performance of an alkaline polymer electrolyte fuel cell (APEFC), it is also necessary to understand the transport processes for the hydroxyl (OH^-) ion in anion exchange membranes. In the present review, the radiation grafting of the monomer and chemical modification to introduce cationic charges/moiety are emphasized. In follow-up, the recent advances in the synthesis of anion exchange membranes from poly(phenylene oxide) via chloromethylation and quaternization, and from aliphatic polymers such as poly(vinyl alcohol) and chitosan via direct quaternization are highlighted. Overall, this review concisely provides an in-depth analysis of recent advances in anion exchange membrane (AEM) and its viability in APEFC.

Pencil Graphite Electrodes Decorated with Platinum Nanoparticles as Efficient Electrocatalysts for Hydrogen Evolution Reaction

Platinum-based materials are widely known as the most utilized and advanced catalysts for hydrogen evolution reaction. For this reason, several studies have reported alternative methods of incorporating this metal into more economical electrodes with a carbon-based support material. Herein, we report on the performance of pencil graphite electrodes decorated with electrochemically deposited platinum nanoparticles as efficient electrocatalysts for hydrogen evolution reaction. The electrodeposition of platinum was performed via pulsed current electrodeposition and the effect of current density on the electrocatalytic activity was investigated. The obtained electrodes were characterized using cyclic voltammetry, while the electrocatalytic activity was assessed through linear sweep voltammetry. Field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy were utilised to gain an insight into surface morphology and chemical analysis of platinum nanoparticles. The best performing electrocatalyst, at both low and high current densities, was characterized by the highest exchange current density of 1.98 mA cm^-2 and an ultralow overpotential of 43 mV at a current density of 10 mA cm^-2. The results show that, at low current densities, performances closest to that of platinum can be achieved even with an ultralow loading of 50 µg cm^-2 Pt.