Chemical Design of Palladium‐Based Nanoarchitectures for Catalytic Applications

Abstract

Palladium (Pd) plays an important role in numerous catalytic reactions, such as methanol and ethanol oxidation, oxygen reduction, hydrogenation, coupling reactions, and carbon monoxide oxidation. Creating Pd‐based nanoarchitectures with increased active surface sites, higher density of low‐coordinated atoms, and maximized surface coverage for the reactants is important. To address the limitations of pure Pd, various Pd‐based nanoarchitectures, including alloys, intermetallics, and supported Pd nanomaterials, have been fabricated by combining Pd with other elements with similar or higher catalytic activity for many catalytic reactions. Herein, recent advances in the preparation of Pd‐based nanoarchitectures through solution‐phase chemical reduction and electrochemical deposition methods are summarized. Finally, the trend and future outlook in the development of Pd nanocatalysts toward practical catalytic applications are discussed.

Recent Progress of Ultrathin 2D Pd‐Based Nanomaterials for Fuel Cell Electrocatalysis

“…This indicates that the ORR presents a complex mechanism and undesirable side reactions, which results in a high activation energy and overpotential, and ultimately, a low electrocatalytic performance of working devices. [ 111–114 ] Therefore, a deeper understanding of the ORR mechanism is very important. The complete electrochemical ORR involves four coupled proton and electron transfers, which result in several reaction pathways: 1)the direct four‐electron electroreduction of OH − ions or H 2 O (in basic or acidic solution, respectively), 2)a two‐electron reaction pathway for the electroreduction of O 2 to H 2 O 2 , 3)a combination of four and two‐electron transfer reduction reactions, 4)an associative mechanism involving the adsorption of O 2 and direct proton/electron transfer to O 2 and OOH group, which leads to the formation of atomic O and OH groups, 5)a dissociative mechanism, which includes the cleavage of OO bonds of O 2 and the hydrogenation of atomic O and OH groups to H 2 O. …”

“…As illustrated in Scheme , 2D nanostructures, particularly 2D Pd‐based metallic nanosheets with single or a few atoms thickness, have attracted increasing interest owing to their multiple inherent advantages compared to their bulk counterparts. [ 55,98,114 ] Among various structural merits, the numerous surface active sites could be the most important parameter that affects the electrocatalytic performance of 2D Pd‐based nanosheets. This has been ascribed to 2D ultrathin Pd‐based nanosheets possessing abundant edge sites, steps, kinks, and low‐coordinated atoms, which could serve as active sites for improving electrochemical performance.…”

Hydrogen Evolution and Oxygen Reduction Reactions in Acidic Media Catalyzed by Pd4S Decorated N/S Doped Carbon Derived from Pd Coordination Polymer

“…[ 6,7 ] However, the low earth‐abundance, high costs, and easy to be poisoned by reaction intermediates result in unsuitable for large scale application in energy techniques. In this case, Pd is much more abundant than platinum, which might have a considerable benefit as electrocatalytic material candidates encompassing a wide variety of applications, such as energy conversion, [ 8 ] specific organic reactions, [ 9 ] and electrochemical sensors. [ 10,11 ] Thus, it is necessary to explore a new kind of non or less noble metal catalysts with the superior catalytic performance to or comparable with Pt/C catalysts.…”

In Search of Excellence: Convex versus Concave Noble Metal Nanostructures for Electrocatalytic Applications

“…[ 1 ] In particular, noble metals play an important role in the electrooxidation of hydrogen and liquid fuels, the electroreduction of oxygen and carbon dioxide, and the hydrogen and oxygen evolution reactions. [ 2–4 ] For instance, in direct alcohol fuel cells (DAFCs), a noble metal catalyst is the most important constituent of the membrane electrode assembly where the catalytic reaction occurs. Because these metals are expensive, it is necessary to maximize their activity per mass unit to ensure the economic viability of DAFCs.…”