A Review on Recent Developments and Prospects for the Oxygen Reduction Reaction on Hollow Pt‐alloy Nanoparticles

Abstract

Due to their interesting electrocatalytic properties for the oxygen reduction reaction (ORR), hollow Pt-alloy nanoparticles (NPs) supported on high-surface-area carbon attract growing interest. However, the suitable synthesis methods and associated mechanisms of formation, the reasons for their enhanced specific activity for the ORR, and the nature of adequate alloying elements and carbon supports for this type of nanocatalysts remain open questions. This Review aims at shedding light on these topics with a special emphasis on hollow PtNi NPs supported onto Vulcan C (PtNi/C). We first show how hollow Pt-alloy/C NPs can be synthesized by a mechanism involving galvanic replacement and the nanoscale Kirkendall effect. Nickel, cobalt, copper, zinc, and iron (Ni, Co, Cu, Zn, and Fe, respectively) were tested for the formation of Pt-alloy/C hollow nanostructures. Our results indicate that metals with standard potential -0.4<E<0.4 V (vs. the normal hydrogen electrode) and propensity to spontaneously form metal borides in the presence of sodium borohydride are adequate sacrificial templates. As they lead to smaller hollow Pt-alloy/C NPs, mesoporous carbon supports are also best suited for this type of synthesis. A comparison of the electrocatalytic activity towards the ORR or the electrooxidation of a CO monolayer, methanol or ethanol of hollow and solid Pt-alloy/C NPs underlines the pivotal role of the structural disorder of the metal lattice, and is supported by ab initio calculations. As evidenced by accelerated stress tests simulating proton-exchange membrane fuel cell cathode operating conditions, the beneficial effect of structural disorder is maintained on the long term, thereby bringing promises for the synthesis of highly active and robust ORR electrocatalysts.

Small-angle scattering by supported nanoparticles: exact results and useful approximations

“…The catalyst consists of the Vulcan XC72 support doped with PtNi nanoparticles, the amount of Ni (a few at.%) being low compared to the amount of Pt. Electron microscopy indicates that the nanoparticles are hollow, with an external diameter of approximately 12 nm and shell thickness of the order of 3 nm (Asset et al, 2018). The overall metal loading of the catalyst is 20 wt% metal over carbon.…”

“…The catalyst was developed for the oxygen reduction reaction at the cathode of proton-exchange membrane fuel cells. Its synthesis and electron microscopy characterization are thoroughly described elsewhere (Asset et al, 2018(Asset et al, , 2019. Fig.…”

Platinum Group Nanowires for Efficient Electrocatalysis

“…Recent years have witnessed the huge success and wide application of PG catalysts in different kinds of electrochemical reactions since they generally exhibit high catalytic activity and excellent stability compared with the nonprecious metal catalysts . For example, Pt is regarded as the best oxygen reduction reaction (ORR) catalyst because of the optimized absorption and desorption binding to the intermediates . It also shows the lowest overpotential in hydrogen evolution reaction (HER) in acidic condition due to its optimal H atom binding energy .…”

“…[10][11][12] For example, Pt is regarded as the best oxygen reduction reaction (ORR) catalyst because of the optimized absorption and desorption binding to the intermediates. [13] It also shows the lowest overpotential in hydrogen evolution reaction (HER) in acidic condition due to its optimal H atom binding energy. [14] Ir and Ru and their oxides are regarded as "the Holy Grail" of 5) The nanowires are conducive to recycling.…”

Synthesis of Sn/Ag–Sn nanoparticles via room temperature galvanic reaction and diffusion

“…Sn nanoparticles (NPs) have been used as phase change materials, 1 for gas-sensing, 2 conductive inks for printed electronics, 3,4 lead-free solder in electronics and anode material in lithium and sodium-ion batteries. [5][6][7][8] Similar to various alloy NPs, [9][10][11][12] the catalytic properties, [13][14][15][16][17] conductivity, 18,19 and soldering properties 20,21 can be further modied and improved by introducing Ag into the Sn NPs to form Ag-Sn alloy NPs. [13][14][15][16][18][19][20][21] The catalytic properties of Ag-Sn NPs were superior compared with that of Sn.…”