Acta Physico-Chimica Sinica ›› 2020, Vol. 36 ›› Issue (9): 1912049.doi: 10.3866/PKU.WHXB201912049

Special Issue: Precise Nanosynthesis

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Rh-Doped PdCu Ordered Intermetallics for Enhanced Oxygen Reduction Electrocatalysis with Superior Methanol Tolerance

Menggang Li1,2, Zhonghong Xia2, Yarong Huang1, Lu Tao2, Yuguang Chao2, Kun Yin2, Wenxiu Yang2, Weiwei Yang1,*(), Yongsheng Yu1,*(), Shaojun Guo2,3,*()   

  1. 1 MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
    2 Department of Materials Science & Engineering, College of Engineering, Peking University, Beijing 100871, P. R. China
    3 BIC-ESAT, College of Engineering, Peking University, Beijing 100871, P. R. China
  • Received:2019-12-19 Accepted:2020-02-26 Published:2020-03-06
  • Contact: Weiwei Yang,Yongsheng Yu,Shaojun Guo E-mail:yangww@hit.edu.cn;ysyu@hit.edu.cn;guosj@pku.edu.cn
  • Supported by:
    the Beijing Natural Science Foundation, China(JQ18005);the National Key R & D Program of China(2016YFB0100201);the National Natural Science Foundation of China(51671003);the National Natural Science Foundation of China(21802003);the National Natural Science Foundation of China(51571072);the National Natural Science Foundation of China(51871078);the China Postdoctoral Science Foundation(2018M631239)

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Abstract:

Direct methanol fuel cells (DMFCs), as one of the important energy conversion devices, are of great interest in the fields of energy, catalysis and materials. However, the application of DMFCs is presently challenged because of the limited activity and durability of cathode catalysts as well as the poisoning issues caused by methanol permeation to the cathode during operation. Herein, we report a new class of Rh-doped PdCu nanoparticles (NPs) with ordered intermetallic structure for enhancing the activity and durability of the cathode for oxygen reduction reaction (ORR) and achieving superior methanol tolerance. The disordered Rh-doped PdCu NPs can be prepared via a simple wet-chemical method, followed by annealing to convert it to ordered phases. The results of transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), power X-ray diffraction (PXRD) analysis and high resolution TEM (HRTEM) successfully demonstrate the formation of near-spherical NPs with an average size of 6.5 ± 0.5 nm and the conversion of the phase structure. The complete phase transition temperatures of Rh-doped PdCu NPs and PdCu are 500 and 400 ℃, respectively. The molar ratio of Rh/Pd/Cu in the as-synthesized Rh-doped PdCu NPs is 5/48/47. Benefitting from Rh doping and the presence of the ordered intermetallic structure, the Rh-doped PdCu intermetallic electrocatalyst achieves the maximum ORR mass activity of 0.96 A·mg-1 at 0.9 V versus reversible hydrogen electrode (RHE) under alkaline conditions—a 7.4-fold enhancement compared to the commercial Pt/C catalyst. For different electrocatalysts, the ORR activities follow the sequence, ordered Rh-doped PdCu intermetallics > ordered PdCu intermetallics > disordered Rh-doped PdCu NPs > disordered PdCu NPs > commercial Pt/C catalyst. In addition, the distinct structure endows the Rh-doped PdCu intermetallics with highly stable ORR durability with unaltered half-wave potential (E1/2) and mass activity after continuous 20000 cycles, which are higher than those of other electrocatalysts. Furthermore, the E1/2 of the Rh-doped PdCu intermetallics decreases by only 5 mV after adding 0.5 mol·L-1 methanol to the electrolyte, while the commercial Pt/C catalyst negatively shifts by 235 mV and a distinct oxidation peak can be observed. The results indicate that the ORR activity of the Rh-doped PdCu intermetallic electrocatalyst can be well maintained even in the presence of poisoning environment. Our results have demonstrated that Rh-doped PdCu NPs with ordered intermetallic structures is a potential electrocatalyst toward the next-generation high-performance DMFCs.

Key words: Rh doping, Ordered intermetallics, Nanoparticle, Oxygen reduction, Methanol tolerance