One-pot synthesis of ultrafine trimetallic PtPdCu alloy nanoparticles decorated on carbon nanotubes for bifunctional catalysis of ethanol oxidation and oxygen reduction

A probable catalytic mechanism of EOR and ORR on PtPdCu/CNTs was summarized, where: (i) The highly dispersed ultrafine ternary alloy nanoparticles give rise to an excellent bifunctional catalytic activity. (ii) The introduction of Pd/Cu into Pt lowers the d-band center of Pt, leading to the accelerated desorption of carbonaceous species. (iii) The Pd/Cu dopant favors the generation of hydroxyl radicals, resulting in facilitated removal of intermediates on Pt sites. (iv) The introduction of the carboxyl (2%) modified CNT is beneficial for effectively anchoring the metal nanoparticles, promoting the mass transfer and regulating the electron transfer. [Display omitted] •PtPdCu/CNTs was fabricated via a surfactant-free one-pot solvothermal synthesis.•PtPdCu nanoparticles at ∼5 nm can be homogenously dispersed on CNTs.•PtPdCu/CNTs exhibit high activity and good stability for EOR and ORR.•XPS and DFT studies reveal the lowered d band center of Pt upon Pd-Cu alloying.•DFT calculations implies a favored C1-path on PtPdCu/CNTs during EOR. Bifunctional catalysts for ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR) with high noble-metal utilization are highly beneficial to direct ethanol fuel cells (DEFCs). This study developed a ternary bifunctional catalyst composed of ultrafine PtPdCu alloy nanoparticles and carbon nanotubes (CNTs) support through a facile surfactant-free solvothermal route. The carboxyl terminal groups on CNTs ensure the confined growth of PtPdCu alloys (∼5 nm) and suppress Ostwald ripening of metallic active sites during electrochemical cycling. Consequently, PtPdCu/CNTs exhibits high mass activity (1.95 A mg−1) and specific activity (4.08 mA cm−2) toward EOR, which are 7.8 and 8.9 times higher, respectively, than those of commercial Pt/C. Furthermore, PtPdCu/CNTs displays superior stability toward EOR compared with its bimetallic counterparts (PtPd/CNTs and PtCu/CNTs). In addition, PtPdCu/CNTs exhibits the highest half-wave potential of 0.888 V among all electrocatalysts, indicating high ORR activity. Density functional theory calculations reveal that Pd and Cu mediate the electronic structure of Pt, leading to enhanced catalytic activity of PtPdCu/CNTs. The excellent catalytic property of PtPdCu/CNTs can also be attributed to the bifunctional effects of Pd/Cu and the interaction between metal and the carbon support. The proposed material is a contribution to the family of efficient ternary-alloy electrocatalysts for fuel ce