Electrocatalytic Activities towards the Electrochemical Oxidation of Formic Acid and Oxygen Reduction Reactions over Bimetallic, Trimetallic and Core–Shell-Structured Pd-Based Materials

Abstract

The structural design of nanosized electrocatalysts is extremely important for cathodic oxygen reduction reactions (ORR) and anodic oxidation reactions in small organic compounds in direct fuel cells. While Pt is still the most commonly used electrode material for ORR, the Pd electrocatalyst is a promising alternative to Pt, because it exhibits much higher electrocatalytic activity towards formic acid electrooxidation, and the electrocatalytic activity of ORR on the Pd electrode is the higher than that of all other precious metals, except for Pt. In addition, the mass activity of Pt in a core–shell structure for ORR can be improved significantly by using Pd and Pd-based materials as core materials. Herein, we review various nanoscale Pd-based bimetallic, trimetallic and core–shell electrocatalysts for formic acid oxidation and ORR of polymer electrolyte fuel cells (PEFCs). This review paper is separated into two major topics: the electrocatalytic activity towards formic acid oxidation over various Pd-based electrocatalysts, and the activity of ORR on Pd-based materials and Pd core–Pt shell structures.

Preparation of Various Pd-Based Alloys for Electrocatalytic CO2 Reduction Reaction—Selectivity Depending on Secondary Elements

“…In addition, Cai et al reported a B-doped Pd electrocatalyst that showed a higher activity for the electrooxidation of formic acid than Pd and a high FE toward the HCOOH formation through the CO 2 reduction reaction . Moreover, for the electrooxidation of HCOOH in an HCOOH-O 2 fuel cell, CO was shown to be formed on the pure Pd surface by the electrochemical reduction reaction of CO 2 produced by HCOOH oxidation rather than HCOOH dehydration. , Therefore, to realize a high FE for HCOOH formation, we believe that it is necessary to create Pd-based materials that can completely suppress the formation of CO from CO 2 reduction.…”

Helium Droplet Mass Spectrometry

“…The extensive research devoted to finding suitable catalysts for direct formic acid fuel cells, a key problem in their commercial application, has found palladium-based catalysts as the best-performing candidate so far [382,383]. Recent investigations have considered nanostructures such as hollow Pd-nanospheres [384], various core-shell nanoparticles [385] as well as Pd and La nanoparticles supported on modified C 60 [386][387][388], which show promise for the use in direct FA fuel cells. Interestingly, little research has been devoted to the study of pure complexes of FA and C 60 .…”

Recent advances in electrocatalysts, mechanism, and cell architecture for direct formic acid fuel cells

“…The above mentioned influences can be rationally promoted in the electrocatalyst by various strategies such as designing a specific morphology, architecture, or structural arrangement (M. Jin et al, 2012; Y. Kim et al, 2012; Maniam et al, 2016; Y. Xu, Yu, et al, 2020; Z. Y. Yu et al, 2020); alloying noble metals with earth‐abundant transition metals (Caglar et al, 2019; Gunji & Matsumoto, 2019); decorating the surface of corrosion‐tolerant cocatalysts with noble metals; and providing better support to disperse catalysts, thereby preventing aggregation using the support's high surface area and conductivity (Ren et al, 2020; X. Zhang, Zhu, et al, 2016). Various reports that have employed these strategies to improve the performance of catalysts toward FAEO are discussed in the subsequent sections.…”

“…Alloying is a common strategy employed to combine the merits of noble metal catalysts with other metals to introduce various effects that would promote FAEO. Three‐dimensional block transitional metals such as Fe, Co, Ni, and Cu are often used as alloying materials with Pt or Pd to modify the electronic properties, mainly by lowering the d‐band centers of Pt or Pd (Gunji & Matsumoto, 2019). The physical and catalytic properties of the metal alloy can be altered by tuning the composition, size, and morphology of the constituent metals.…”