Pulsed Electrodeposition of Metastable Pd₃₁Bi₁₂ Nanoparticles for Oxygen Reduction Electrocatalysis

Abstract

Metastable alloys have recently emerged as high-performance catalysts, extending the toolbox of binary alloy materials that can be utilized to mediate electrocatalytic reactions. In particular, nanostructured metastable ordered intermetallic compounds are challenging to synthesize. Here we report a method for synthesizing sub-15 nm metastable ordered intermetallic Pd31Bi12 nanoparticles at room temperature, in a single step, by pulsed electrochemical deposition onto high surface area carbon supports. The resulting Pd31Bi12 nanoparticles displays a 7× enhancement of the mass activity relative to Pt/C and a 4× enhancement relative to Pd/C for the oxygen reduction reaction (ORR). The high performance of Pd31Bi12 nanoparticles is demonstrated to arise from reduced oxygen binding caused by alloying of Pd with Bi. We also demonstrate that the isolation of Pd sites from each other facilitates methanol-tolerant ORR behavior.

Unravelling charge-transfer in Pd to pyrrolic-N bond for superior electrocatalytic performance

“…7,8,19,20 Very recently, Bi was shown to form alloy NCs with Pd, exhibiting a very high ORR E 1/2 = 0.92 V vs. RHE due to the weakening of the surface Pd-O bonds. 9 However, the activity loss was >40% after 10000 cycles. Overall, the large body of work done to date suggests that a high mass-activity in alloys is accompanied by a rapid loss of performance.…”

“…[1][2][3][4] Recent investigations have shown that the electrocatalytic efficiency of the Pdbased catalysts can be improved systematically and significantly to match those of Pt by adopting innovative design strategies, tailoring their surfaces by means of facet engineering or alloy formation and tuning of substrate-catalyst interactions. [5][6][7][8][9][10][11] However, two outstanding challenges in AFCs while using Pd nanocrystals (NCs) remain to-date: i) overcoming the sluggish ORR kinetics to further reduce the Pd requirement to match a target set by U.S. Department of Energy, and ii) the absence of sustained highcatalytic activity for prolonged time-periods under the electrochemical operating environments. 6,8,12 Therefore in the existing device prototypes, a larger amount of noble metal is loaded on to the electrode surfaces to attain a sufficient durability.…”

“…has emerged as a preferred strategy to modulate the surface electronic structure for improved catalytic activity, and to reduce the noble metal load at the same time. [7][8][9][11][12][13][14][15] The electrons in the 'other' metals hybridize with the d electrons of Pd to lower the 'd-band center' effecting a favorable modulation of the bond-strengths of the ORR intermediates. 16,1718 Besides, the lattice strain invoked by smaller sizes of the alloying atoms also helps in attenuating the intermediate binding energies.…”

“…Overall, the large body of work done to date suggests that a high mass-activity in alloys is accompanied by a rapid loss of performance. 1,9,21 Another general disadvantage in using alloys may arise due to a continuous change of their compositions during catalysis due to the high chemical reactivity of the non-noble components. 11 On the other hand, extremely high stability up to 100000 cycles was achieved recently by using alloy thin-films, but even the initial activities were poorer than the deactivated performances of the nanoparticulate catalysts due to a larger catalyst load.…”

Ultrafast and surfactant-free synthesis of Sub-3 nm nanoalloys by shear-assisted liquid-metal reduction

“…[10][11][12][13][14][15][16][17] Previous studies have shown that Pt-based alloys present good catalytic activity as an ideal catalyst for the hydrogen evolution reaction, oxygen reduction reaction, and ethanol oxidation reaction. [18][19][20][21][22][23][24] At the same time, the alloying of low-cost transition metals and precious metals can effectively reduce the amount of precious metals and control costs. 25 However, current methods of manufacturing alloys are generally complicated and time consuming, and therefore it is very important to develop a convenient, efficient, and rapid method of manufacturing alloys.…”