Sub‐3 nm Intermetallic Ordered Pt₃In Clusters for Oxygen Reduction Reaction

Abstract

Previous works have found that the surface atomic structure and composition of catalysts play critical roles in the electrocatalytic performance of Pt-based catalysts. [5][6][7] Accordingly, nanoalloys with various atomic arrangement style including controlled composition or shape, core-shell structure, heterostructure, hollow structure and ordered structure have been designed and proved to be effective ways to modify the catalytic performance of Pt-based catalyst. [8][9][10][11][12] Furthermore, well-designed alloyed particles with Pt-enriched surfaces should possess a suitable electronic structure for ORR and thus meet both high performance and lower cost. [13] Low-coordination metal atoms often function as the catalytically active sites, while the specific activity per metal atom usually increases with decreasing size of the metal particles. [14,15] Additionally, smaller size also indicates higher dispersion of Pt atoms and higher utilization efficiency. [16] However, the surface free energy of metals increases significantly with decreasing particle size, promoting aggregation of small clusters. [17] Monodispersed superfine alloyed clusters have many advantages, such as high Pt-utilization efficiency and synergistic effects arising from neighboring metal atoms. [18] More importantly, by forming ordered intermetallic PtM nanocrystals with some metal M, the higher mixing enthalpy and stronger atomic interactions between Pt and M atoms would make PtM highly stable under electrochemical tests in both acidic and alkaline solutions. [19][20][21][22] However, in general, forming Industrial applications of Pt-based oxygen-reduction-reaction (ORR) catalysts are limited by high cost and low stability. Here, facile large-scale synthesis of sub-3-nm ordered Pt 3 In clusters on commercial carbon black as ORR catalyst that alleviates both these shortcomings is reported. As-prepared Pt 3 In/C exhibits a mass activity of 0.71 mA mg −1 and a specific area activity of 0.91 mA cm −2 at 0.9 V vs reversible hydrogen electrode, which are 4.1 and 2.7 times the corresponding values of commercial Pt/C catalysts. The asprepared ordered Pt 3 In/C catalyst is also remarkably stable with negligible activity and structural decay after 20 000 accelerated electrochemical durability cycles, due to its ordered structure. Density-functional-theory calculations demonstrate that ordered-Pt 3 In is more energetically favorable for ORR than the commercial Pt/C catalysts because ∆G O is closer to the peak of the volcano plot after ordered incorporation of indium atoms.

Oxygen Reduction Electrocatalysts toward Practical Fuel Cells: Progress and Perspectives

“…[51][52][53][54] Contrary to the disordered alloys,t he ordered intermetallics have specific arrangements of Pt and transition metals with ap recise crystal lattice properties.O rdered alloy provides biaxial strain with tension in one particular direction and compression in the other, which endows remarkable changes in electrochemical behavior of PtM alloys. [39] Different kind of ordered alloys have been reported with significantly improved structural and electrocatalytic properties than their counter disordered alloys,e .g., binary PtCo, [55][56][57] PtCo 3 , [58] PtFe, [45] PtIn, [59] CoPt, [60] ternary PtNiCo. [61] Controlling particle size in intermetallics is highly desirable,a s most of the intermetallics are prepared by annealing at high temperature,where avoiding particle aggregation is challenging.…”

Pt-Based Intermetallic Nanocrystals in Cathode Catalysts for Proton Exchange Membrane Fuel Cells: From Precise Synthesis to Oxygen Reduction Reaction Strategy

“…After acid treatment, the alloying effect of PtIn core makes the catalyst possess excellent ORR performance, with negligible decay of structure and activity after the 20,000 cycles ADT. The DFT calculations demonstrate that the introduction of In atoms can also optimize the oxygen adsorption energy on the NP surface, which further enhances the ORR activity of the catalyst [168]. Its stability is even better than that of the conventional ORR catalysts such as PtFe, PtCo and PtNi NPs in terms of the MEA test.…”

An Overview on Pt3X Electrocatalysts for Oxygen Reduction Reaction

“…They found Pt 3 Cu to exhibit the highest mass activity amongst all other compositions attributed to the formation of Cu oxide species and redissolution/redeposition of the Cu species during the voltage cycling [44] . DFT calculations showed that ordered Pt 3 In is more favourable for ORR since ΔG 0 reaches more closer to the peak of the volcano plot after incorporation of ordered indium atoms [45] …”