Fully Ordered and Trace Au‐Doped Intermetallic PdFe Catalyst with Extra High Activity and Durability toward Oxygen Reduction Reaction

Abstract

Developing Pt-free catalysts with high activity and durability is considered as an essential step for cost reduction and real commercialization of fuel cells. Previous Pt-free catalysts are either lack of activity and/or insufficient in durability. Here we report the first synthesis of a carbon-supported PdFe catalyst with a fully ordered intermetallic structure by controlling the atomic ratio of Pd and Fe and high-temperature annealing for structural ordering. This intermetallic catalyst is then doped with a trace amount of Au (atomic ratio of Au/Pd: 1/50) mainly in the surface region of the ordered lattice. Such an Au-doped intermetallic PdFe catalyst is finally demonstrated to possess a comparable catalytic activity and much better durability for oxygen reduction reaction than the commercial catalyst of Pt/ C. For example, the half-wave potential of the Au-PdFe catalyst decreases at a rate 9 times slower than that of Pt/C catalyst after potential cycling under harsh electrochemical conditions. The excellent activity and durability of this new catalyst is attributed to the ordered structure of PdFe particles and the protective effect of the surface Au doping. This study provides a new strategy to developing Pt-free catalysts, lowering the production cost, and accelerating the practical application of fuel cells.

Electrochemical Energy Conversion on Intermetallic Compounds: A Review

“…Based on elemental analysis and EELS results, the authors conclude that the Pt ratio in their study was too low (Pt/Pd = 1/70) to form a complete monolayer, which is also true for work on AuCu@Pt as well as disordered alloy nanoparticles. − A formula to calculate the Pt layer thickness based on Pt content and nanoparticle size was established . Ordered FePd nanoparticles with a gold decorated Pd shell were prepared by reducing iron- prior to palladium-precursors on a carbon support, followed by annealing at 900 °C . Au was introduced by chemically replacing surface iron atoms and consecutive reannealing at 500–900 °C.…”

“…118 Ordered FePd nanoparticles with a gold decorated Pd shell were prepared by reducing iron-prior to palladium-precursors on a carbon support, followed by annealing at 900 °C. 122 Au was introduced by chemically replacing surface iron atoms and consecutive reannealing at 500−900 °C. Higher reannealing temperatures lead to better durabilities in ADTs.…”

Ordered intermetallic compounds combining precious metals and transition metals for electrocatalysis

“…As mentioned earlier, ordered structures have unique advantages in achieving higher electrocatalytic activity and stability than disordered structures. (Xiao et al, 2018b;Wu et al, 2018;Kang et al, 2020;Luo et al, 2020;Gong et al, 2021) Inspired by the synthesis of ordered PtFe intermetallic compounds, more and more researchers strive to prepare cheaper ordered PdFe as an alternative to Pt-based electrocatalysts. Just like ordered PtFe, the successful synthesis of ordered PdFe is also demonstrated by the existence of "ordered peaks" in the XRD patterns.…”

“…As mentioned earlier, ordered structures have unique advantages in achieving higher electrocatalytic activity and stability than disordered structures. ( Xiao et al, 2018b ; Wu et al, 2018 ; Kang et al, 2020 ; Luo et al, 2020 ; Gong et al, 2021 )…”

“…Compared with traditional alloys/single metal nanoparticles, the ordered intermetallic compounds have two advantages: 1) Each crystal position of intermetallic compounds is occupied by a specific atom, so that the structure, geometric effects and electronic effects can be controlled; 2) The formation enthalpy between the noble metal and the second metal M is more negative in ordered intermetallic compounds, and this strong interaction can provide long-term stability and avoid catalyst deactivation. ( Xiao et al, 2018a ; Wu et al, 2018 ; Peera et al, 2019 ; Sun et al, 2019 ; Mondal et al, 2020 ; Yuan et al, 2021 ) The current ordered intermetallic compounds are divided into PtM and PdM, M is a transition metal (M = Cu, Fe, Ni, Co, etc.). Compared with Pd-based ordered intermetallic compounds, Pt-based ordered intermetallic compounds have more in-depth research, and are more accurate for the control of near-surface active sites.…”