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Herein, we report the synthesis of carbon-supported palladium–nickel electrocatalysts (ECs) (Pd4–x Ni x /C ECs, x = 1–3) as an important class of non-platinum ECs, for both oxygen reduction reaction (ORR) and formic acid oxidation (FAO) reactions. Among various as-synthesized ECs, the Pd3Ni/C catalyst exhibited the best performance, which outperforms the benchmark Pt/C and Pd/C catalysts. For ORR, the onset potential of Pd3Ni/C EC (0.96 V) is 40 and 80 mV more positive than that of the benchmark Pt/C (0.92 V) and Pd/C (0.88 V) catalysts, suggesting its remarkable ORR behavior. All Pd4–x Ni x /C (x = 1–3) compositions favored the “4e” reduction pathway during ORR in alkaline media. Furthermore, the ECs are very efficient toward the FAO reaction, which proceeds via the “dehydrogenation” pathway. The electrochemically active surface area of Pd3Ni/C EC is found to be ∼2-, ∼4-, ∼5-, and ∼35-fold higher than that of PdNi/C, PdNi3/C, Pd/C, and standard Pd/C ECs, respectively. The remarkable ORR/FAO activity of the synthesized ECs can be ascribed to the homogeneous dispersion of smaller palladium–nickel alloy nanoparticles over the carbon support, downshift of Pd d-band center, as well as synergistic effect between the metals that makes electron transfer easier. Meanwhile, the downshift of the Pd d-band center after alloying with Ni was confirmed via density functional theory calculations, which unveiled the superiority of Pd3Ni/C over other ECs and the benchmarks. Thus, this work represents a cost-effective and ecofriendly approach for designing high-performance anode as well as cathode catalytic materials for practical applications.

Herein, we report the synthesis and bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities of a CuO x −CeO 2 /C electrocatalyst (EC) with rich oxide−oxide and oxide−carbon interfaces. It not only demonstrates a smaller Tafel slope (65 mV dec −1 ) and higher limiting current density (−5.03 mA cm −2 ) but also exhibits an onset potential (−0.10 V vs Ag/AgCl) comparable to that of benchmark Pt/C. Besides undergoing the favorable direct four-electron ORR pathway, it unveils a loss of 23% of its initial current after 6 h of a stability test and a negative shift of 4 mV in the half-wave potential after the accelerated durability test compared to the corresponding current loss of 28% and negative shift of 20 mV for Pt/C. It also reveals remarkable OER activity in an alkaline medium with a low onset potential (0.20 V) and a smaller Tafel slope (177 mV dec −1 ). The bifunctional ORR/OER activity of CuO x −CeO 2 /C EC can be ascribed to the synergistic effects, its unique structure with enriched oxygen vacancies owing to the presence of Ce 4+ /Ce 3+ , robust oxide−oxide and oxide−carbon heterointerfaces, and homogeneous dispersion of oxides over the carbon bed, which facilitates faster electronic conduction.

A unique and novel structural morphology with advantageous surface defects, lattice strain, and a preferentially exposed crystal plane are indispensable criteria for offering superior and durable electrocatalytic performance. However, the design of a single electrocatalyst (EC) with all such splendors is still a challenging task. Here, we successfully developed a one pot, surfactant and organic structure directing agent free alternative EC based on Pd2CuCo/C hybrid with nanoflower (NF) morphology. The efficacy of electrode is offered by highly open hierarchical nanostructures with a preferentially exposed (111) plane and multiple surface defects. Moreover, the half implanted Pd2CuCo on a carbon matrix offers high stability and the metal/carbon interface provides faster electron transfer during the fuel cell operation process. Remarkably, Pd2CuCo/C NF shows significant electrocatalytic activity toward the oxygen reduction reaction (ORR). A current density of 5.5 mA cm–2, an onset potential of −0.018 V (vs Ag/AgCl), and a half-wave potential of −0.138 V were noted for the ORR of Pd2CuCo/C NF. It delivered good methanol tolerance and enhanced stability with ∼80.3% of the retention current, even after 21,600 sec at 1600 rpm, unlike the benchmark Pt/C catalyst. Moreover, computational studies show that Co and Cu doping in Pd2CuCo/C alloy NF will inhibit the degradation of the electrocatalytic activity caused by strong CO adsorptions. The greater accessible active sites, the strong interfacial interaction between Pd2CuCo NF and the carbon matrix, and the excellent synergistic interaction between Pd and Cu, Co are the major marvels for such superior electrocatalytic performance. Therefore, the present investigation offers a promising approach of designing high-performance non-Pt ECs.