Depositing the PtNi nanoparticles on niobium oxide to enhance the activity and CO-tolerance for alkaline methanol electrooxidation

Abstract

Direct methanol fuel cells have the advantages of simple system, convenient operation, high conversion rate and low carbon emission, which are considered as the environmental and friendly energy conversion devices. However, the low activity, CO-tolerance and high cost of anode catalysts restrict the large-scale commercial applications. Therefore, it is of great practical significance to design and construct the anodic catalysts with high activity, stability and low cost for methanol oxidation reaction. In this work, the PtM/Nb2O5–C (M = Co, Sn, Ni) catalysts are synthesized by the ethylene glycol solvothermal method using transition metal oxide Nb2O5 as the support. The catalytic performance of different catalysts is further evaluated for alkaline MOR. The results show that the introduction of Ni (existing in Ni2+ and Ni3+) has the most obvious improvement for alkaline MOR performance. By adjusting the doped ratio of Pt:Ni, it is shown that PtNi/Nb2O5–C has the highest mass activity (3877.9 mA·mgPt−1), 12 times that of the commercial Pt/C catalyst. CV, LSV, Tafel and EIS analyses show that PtNi/Nb2O5–C has the lowest onset potential and charge transfer resistance, and the fastest electrocatalytic oxidation rate of methanol. CA tests show that the electrochemical stability is also significantly improved with the introduction of Nb2O5 and Ni. Combined with the structural characterization and electrochemical tests, it is found that the evident electronic effect among Pt and Ni, Nb2O5 and the hydroxyl brought from Ni species are mainly ascribed for enhancing the activity, CO resistance and stability of PtNi/Nb2O5–C.