Octahedral Pd3Cu7 Catalysts on Diverse Support Materials for Efficient Hydrogen Evolution: Theoretical Investigation and Mechanistic Perspective.

This work showcases a novel strategy for the synthesis of shape-dependent alloy nanostructures with the incorporation of solid substrates, leading to remarkable enhancements in the electrocatalytic performance. Herein, an aqueous medium approach has been used to synthesize an octahedral PdXCuY alloy of different Pd:Cu ratios to better comprehend their electrocatalytic potential. With the aim to outperform high activity and efficient stability, zirconium oxide (ZrO2), graphene oxide nanosheets (GONs), and hexagonal boron nitride nanosheets (hBNNs) solid substrates are occupied to decorate the optimized Pd3Cu7 catalyst with a minimum 5 wt % metal loading. When compared to the counterparts and different ratios, the Pd3Cu7@hBNNs catalyst exhibited an optimal activity for hydrogen evolution reaction (HER). The lower overpotential and Tafel values observed are 64 and 51 mV/dec for Pd3Cu7@hBNNs followed by Pd3Cu7@ZrO2, which showed a 171 mV overpotential and a 98 mV/dec Tafel value, respectively. Meanwhile, the Pd3Cu7@GONs were found to have a 202 mV overpotential and a 110 mV/dec Tafel value. The density functional theory, which achieves a lower free energy (ΔGH*) value for Pd3Cu7@hBNNs than the other catalysts for HER, further supports its excellent performance in achieving the Volmer-Heyrovsky mechanism path. Moreover, the superior HER activity and sturdier resilience after 8 h of stability may be due to the synergy between the metal atoms, monodisperse decoration, and the coordination effect of the support material.

Modern Chemical Routes for the Controlled Synthesis of Anisotropic Bimetallic Nanostructures and Their Application in Catalysis.

Bimetallic nanoparticles (BNPs) have attracted greater attention compared to its monometallic counterpart because of their chemical/physical properties. The BNPs have a wide range of applications in the fields of health, energy, water, and environment. These properties could be tuned with a number of parameters such as compositions of the bimetallic systems, their preparation method, and morphology. Monodisperse and anisotropic BNPs have gained considerable interest and numerous efforts have been made for the controlled synthesis of bimetallic nanostructures (BNS) of different sizes and shapes. This review offers a brief summary of the various synthetic routes adopted for the synthesis of Palladium(Pd), Platinum(Pt), Nickel(Ni), Gold(Au), Silver(Ag), Iron(Fe), Cobalt(Co), Rhodium(Rh), and Copper(Cu) based transition metal bimetallic anisotropic nanostructures, growth mechanisms e.g., seed mediated co-reduction, hydrothermal, galvanic replacement reactions, and antigalvanic reaction, and their application in the field of catalysis. The effect of surfactant, reducing agent, metal precursors ratio, pH, and reaction temperature for the synthesis of anisotropic nanostructures has been explained with examples. This review further discusses how slight modifications in one of the parameters could alter the growth mechanism, resulting in different anisotropic nanostructures which highly influence the catalytic activity. The progress or modification implied in the synthesis techniques within recent years is focused on in this article. Furthermore, this article discussed the improved activity, stability, and catalytic performance of BNS compared to the monometallic performance. The synthetic strategies reported here established a deeper understanding of the mechanisms and development of sophisticated and controlled BNS for widespread application.

Controlled Synthesis of Palladium Nanocubes as an Efficient Nanocatalyst for Suzuki-Miyaura Cross-Coupling and Reduction of p-Nitrophenol.

Anisotropic nanocatalysts have attracted considerable attention in comparison to bulk/nanocatalysts for their enhanced activity and reactivity. The demand toward anisotropic palladium (Pd) nanostructures has increased rapidly in the field of catalysis. Pd is a well-known active catalyst for several carbon-carbon (C-C) cross-coupling reactions; among them, the Suzuki-Miyaura cross-coupling reaction is one of the most versatile and dominant methods for constructing the extraordinarily useful unsymmetrical biaryls and also for hydrogenation of organic contaminants like p-nitrophenol (p-NP). This paper provides a brief explanation about the controlled synthesis, characterization, and catalytic activity of well-defined palladium nanocubes (Pd NCs) prepared by a seed-mediated method. The synthesized monodispersed Pd NCs were characterized by spectroscopic and microscopic tools such as UV-visible, XRD, FESEM, HRTEM, and EDS analyses. Pd NCs proved as an efficient catalyst for Suzuki-Miyaura cross-coupling reactions and p-NP reduction. The catalyst shows enhanced activity, greater stability, and higher selectivity with remarkable recyclability up to 92% for five consecutive cycles. The catalytic performance of the synthesized Pd NCs was also studied in the reduction of the organic contaminant p-NP, which showed an excellent performance screening of 99% conversion in 6 min.