Coupling the oxyphilic metals and NbN to modulate the electronic structure of Pd and enhance the efficiency for alkaline MOR

It is essential to design and produce stable, high-activity, and low-cost anode catalysts for direct methanol fuel cells (DMFCs). To improve the efficiency of the methanol oxidation reaction (MOR) in alkaline media, a series of PdM-NbN/C (M=Co, Ni, Cu) bi-component catalysts were synthesized by introducing various oxyphilic metals. Electrochemical evaluations show that the presence of Ni and Co significantly enhances catalytic activity, charge transfer kinetics, CO tolerance, and long-term stability compared to Pd-NbN/C. Among these, PdNi-NbN/C exhibits the highest mass activity of 4806.67 A·g Pd −1 , the lowest onset potential and charge transfer resistance, as determined from electrochemical testing. The rate-determining step (RDS) is identified as the CO ads oxidation reaction. Characterization analysis confirms that the second oxyphilic metals primarily optimize the Pd electronic structure and modulate the interaction between Pd and NbN, making a favorable shift in the d-band centers. Additionally, Ni and Co elements tend to form hydroxides in higher proportions, which aids in the removal of CO ads and accelerates the RDS. The electronic interactions between Pd, Ni, and NbN species are key to the enhanced catalytic performance for MOR. Pd nanoparticles in the electron-deficient condition may aid in the activation of methanol and its intermediates, as indicated by the linear relationship between the mass activities and d-band centers. This work offers important information for the logical design of efficient anode catalysts for DMFCs.