Synthesis of low‐cost Co‐Sn‐Pd/rGO catalysts via ultrasonic irradiation and their electrocatalytic activities toward oxygen reduction reaction

Abstract

Reduced graphene supported Co-Sn-Pd nanoparticle catalysts(Co 0.2 Sn x Pd y / rGO, x + y = 0.4) were successfully synthesized by reducing the trace amounts of ions (Pd 2+ , Sn 2+ , and Co 2+ ) in the presence of reduced graphene via an ultrasonic irradiation method. Characterization of the Co 0.2 Sn x Pd y /rGO catalysts by X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicates that the Co 0.2 Sn 0.2 Pd 0.2 /rGO catalyst with a mean diameter of $3.8 nm is close to a single-phase solid solution. X-ray photoelectron spectroscopy (XPS) shows the binding energy of metallic Pd shifts to a higher angle in the Co 0.2 Sn x Pd y /rGO (x + y = 0.4) catalysts, indicating a shift of Pd electronic centre upon alloying with Co and Sn. Conventionally, ternary Co-Sn-Pd/rGO catalysts show greater oxygen reduction reaction (ORR) activities and durability than binary Pd-Co/rGO catalyst and 20 wt% Pt/C catalyst even at a very low Pd content. Among of the synthetic catalysts, the Co 0.2 Sn 0.2 Pd 0.2 /rGO catalyst exhibits the best ORR activity (E 1/2 = 0.91 V, k = −57 mV Á dec −1 ) and dominates a 4-electron pathway in the ORR process (n = 3.95 ± 0.09, H 2 O 2 <4%). Also, the Co 0.2 Sn x Pd y /rGO (x + y = 0.4) catalysts display a remarkable advantage of high methanol tolerance compared to that of the commercial 20 wt% Pt/C catalyst, which make them potential candidates for direct methanol fuel cells.

Electronic Modulation of Pd/C by Simultaneous Doping of Cu and Co Tendering a Highly Durable and Methanol-Tolerant Oxygen Reduction Electrocatalyst

“…Similarly, the Pd 2 CuCo/C hybrid exhibits a superior half-wave potential to most of the reported electrocatalysts such as Pd 1 Ni 1 Cu 0.8 /C, Au@Pd/rGO, G-Cu 3 Pd, and GN@Pd-GA . Moreover, the as-synthesized electrocatalysts displayed a much lower Tafel slope (58.7 mV dec –1 ) than the other enlisted electrocatalysts and very close to Co 0.2 Sn 0.2 Pd 0.2 /rGO . These results show that Pd 2 CuCo/C has the best intrinsic activity among these reported catalysts.…”

“…45 Similarly, the Pd 2 CuCo/C hybrid exhibits a superior half-wave potential to most of the reported electrocatalysts such as Pd 1 Ni 1 Cu 0.8 /C, 46 Au@Pd/rGO, 47 G-Cu 3 Pd, 49 and GN@Pd-GA. 54 Moreover, the as-synthesized electrocatalysts displayed a much lower Tafel slope (58.7 mV dec −1 ) than the other enlisted electrocatalysts and very close to Co 0.2 Sn 0.2 Pd 0.2 /rGO. 48 These results show that Pd 2 CuCo/C has the best intrinsic activity among these reported catalysts. Furthermore, we have compared the ECSA value, which would be responsible for a notable improvement in the electrocatalyst's performance, for a better understanding of the factors underlying the catalyst's high ORR performance.…”

“…Furthermore, we have compared the ECSA value, which would be responsible for a notable improvement in the electrocatalyst’s performance, for a better understanding of the factors underlying the catalyst’s high ORR performance. Pd 2 CuCo/C exhibits a higher ECSA value than many of the electrocatalysts, ,,,− indicating the presence of more catalytic active sites on the surface of Pd 2 CuCo/C. These superior catalytic performances make the Pd 2 CuCo/C hybrid nanostructure a potential electrocatalyst toward ORR.…”

Ultrasonic-assisted preparation of two-dimensional materials for electrocatalysts

“…Co-Sn-Pd supported on reduced graphene has been prepared through ultrasonic radiation [131] . Even at very low content of Pd, tribasic Co-Sn-Pd/rGO electro-catalysts exhibit higher ORR activity and stability than dibasic Pd-Co/rGO catalysts and 20 wt% Pt/C catalysts.…”