Incorporating oxophilic metals into noble metal-based catalysts represents an emerging strategy to improve the catalytic performance of electrocatalysts in fuel cells. However, effects of the distance between the noble metal and oxophilic metal active sites on the catalytic performance have rarely been investigated. Herein, we report on ultrasmall (∼5 nm) Pd–Ni–P ternary nanoparticles for ethanol electrooxidation. The activity is improved up to 4.95 A per mgPd, which is 6.88 times higher than commercial Pd/C (0.72 A per mgPd), by shortening the distance between Pd and Ni active sites, achieved through shape transformation from Pd/Ni–P heterodimers into Pd–Ni–P nanoparticles and tuning the Ni/Pd atomic ratio to 1:1. Density functional theory calculations reveal that the improved activity and stability stems from the promoted production of free OH radicals (on Ni active sites) which facilitate the oxidative removal of carbonaceous poison and combination with CH3CO radicals on adjacent Pd active sites. Incorporating oxophilic metals into noble metal catalysts can improve electrocatalytic performance; however, the influence of the distance between noble metal and oxophilic metal active site is not well understood. Here the authors make Pd–Ni–P nanocatalysts for ethanol oxidation, with improved performance achieved by shortening the Pd–Ni distance.

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Improved ethanol electrooxidation performance by shortening Pd–Ni active site distance in Pd–Ni–P nanocatalysts

The ethanol oxidation reaction (EOR) has drawn increasing interest in electrocatalysis and fuel cells by considering that ethanol as a biomass fuel has advantages of low toxicity, renewability, and a high theoretical energy density compared to methanol. Since EOR is a complex multiple-electron process involving various intermediates and products, the mechanistic investigation as well as the rational design of electrocatalysts are challenging yet essential for the desired complete oxidation to CO2. This mini review is aimed at presenting an overview of the advances in the study of reaction mechanisms and electrocatalytic materials for EOR over the past two decades with a focus on Pt- and Pd-based catalysts. We start with discussion on the mechanistic understanding of EOR on Pt and Pd surfaces using selected publications as examples. Consensuses from the mechanistic studies are that sufficient active surface sites to facilitate the cleavage of the C–C bond and the adsorption of water or its residue are critical for obtaining a higher electro-oxidation activity. We then show how this understanding has been applied to achieve improved performance on various Pt- and Pd-based catalysts through optimizing electronic and bifunctional effects, as well as by tuning their surface composition and structure. Finally we point out the remaining key problems in the development of anode electrocatalysts for EOR.

Recent Advances on Electro-Oxidation of Ethanol on Pt- and Pd-Based Catalysts: From Reaction Mechanisms to Catalytic Materials

Metal-based electrocatalysts with different sizes (single atoms, nanoclusters, and nanoparticles) show different catalytic behaviors for various electrocatalytic reactions. Regulating the coordination environment of active sites with precision to rationally design an efficient electrocatalyst is of great significance for boosting electrocatalytic reactions. This review summarizes the recent process of heterogeneous supported single atoms, nanoclusters, and nanoparticles catalysts in electrocatalytic reactions, respectively, and figures out the construct strategies and design concepts based on their strengths and weaknesses. Specifically, four key factors for enhancing electrocatalytic performance, including electronic structure, coordination environment, support property, and interfacial interactions are proposed to provide an overall comprehension to readers in this field. Finally, some insights into the current challenges and future opportunities of the heterogeneous supported electrocatalysts are provided.

Design concept for electrocatalysts

Nonaqueous lithium–air batteries have garnered considerable research interest over the past decade due to their extremely high theoretical energy densities and potentially low cost. Significant adv...

Current challenges and routes forward for nonaqueous lithium–air batteries

Recent advances in palladium-based electrocatalysts for fuel cell reactions and hydrogen evolution reaction

Carbon supported Pd–Ni–P nanoalloy as an efficient catalyst for ethanol electro-oxidation in alkaline media

Carbon-supported well-dispersed PdeNieP ternary catalyst targeted for ethanol oxidation reaction (EOR) in alkaline media is synthesized in a simple aqueous bath containing Pd(II) and Ni(II) salts with sodium hypophosphite as the reducing agent and the source for P and sodium citrate as the complexing agent. XRD analysis on the as-prepared PdeNieP/C reveals that Ni shrinks while P expands the Pd lattice structure, and XPS measurement suggests different electronic effects of the two alloying elements on Pd. Cyclic voltammetry and chronoamperometry indicate that the PdeNieP/C presents a remarkably higher electrocatalytic activity than the state-of-the-art Pd/C, PdeP/C and PdeNi/C catalysts. This may be ascribed to the unique electronic, geometric and bifunctional effects involved in this ternary nanoalloy. 2013 Elsevier B.V. All rights reserved.

Carbon Supported Pd-Ni-P Nanoalloy As An Efficient Catalyst for Ethanol Electro-Oxidation in Alkaline Media

Fuel cells, Li-ion batteries, and supercapacitors are attracting extensive attention, and it is highly desired to integrate the advantages of these devices into one system. Herein, a multifunction Li–carbon system was designed by using an aqueous–nonaqueous dual electrolyte to combine a nitrogen-doped ordered mesoporous carbon cathode with a metallic lithium anode. It is demonstrated that the nitrogen-doped ordered mesoporous carbon exhibits high performance in various applications of O2 reduction reaction, supercapacitors, and H2 evolution reaction, which makes the Li–carbon system exhibit multifunctionality. When operated in the ambient with O2, the system can work as a Li–air fuel cell or/and rechargeable battery with high energy density. When operated in an environment without O2, the battery can be used as a Li-ion supercapacitor which exhibits long-term cycling stability and improved energy performance. Finally, this cell can also be applied as a Li–water fuel cell for H2 evolution.

http://pubs.acs.org/doi/pdf/10.1021/acsenergylett.6b00566

Ye Wang

Papers

Recent Advances on Electro-Oxidation of Ethanol on Pt- and Pd-Based Catalysts: From Reaction Mechanisms to Catalytic Materials

Carbon supported Pd–Ni–P nanoalloy as an efficient catalyst for ethanol electro-oxidation in alkaline media

Carbon Supported Pd-Ni-P Nanoalloy As An Efficient Catalyst for Ethanol Electro-Oxidation in Alkaline Media

A Multifunction Lithium–Carbon Battery System Using a Dual Electrolyte

Enhanced Electrocatalysis of Ethanol on Dealloyed Pd-Ni-P Film in Alkaline Media: an Infrared Spectroelectrochemical Investigation