关键词: 低掺杂合金, 电催化剂, 乙醇电氧化, 碱性介质, 性能增强

Among currently reported anodic nano-alloy electrocatlysts for direct alkaline ethanol fuel cells (DAEFCs), the mass fraction (w) of co-catalysts is generally larger than 20%. This could increase the thickness of the catalyst layer in Membrane Electrode Assembly (MEA), which not only decreases the discharge voltage of fuel cells, also reduces the utilization of the noble metals such as Pt and Pd. To solve this problem, here we synthesized a series of Pd-Ni-P alloy electrocatalysts with ultra-low doping amount of Ni and P, using ca. 1.5 mg NaH₂PO₂ as reducing agent. To obtain different doping amount of Ni and P, the pH value of the synthetic solution was adjusted from 8 to 12 by 0.1 mol/L NaOH. Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) results showed that the mass fraction of Ni and P were low to 0.2% and 0.05%, respectively, when the pH value of the synthetic solution is 10. Transmission Electron Microscopy (TEM) images showed that nanoparticles were distributed evenly on the carbon base, and their mean particle sizes increased from ca. 3.78 nm to ca. 5.4 nm with alkalinity of synthetic solutions increasing. Cyclic Voltammograms in 0.5 mol/L CH₃CH₂OH+1 mol/L NaOH solution revealed that the catalyst obtained under the pH 10 synthetic solution (hereafter denoted as Pd-Ni-P/C-pH10) gave a highest apparent current density of ca. 2466 mA•mg^-1 Pd, nearly 2.7 times in respect of that of the commercial Pd/C catalyst (JM). Meanwhile, the durability of Pd-Ni-P/C-pH10 for ethanol oxidation was improved by ca. 2.8 times compared to commercial catalyst. Relative to pure Pd, the binding energy of Pd 3d_5/2of as-prepared catalysts all positively shifted, suggesting an obvious electronic interaction between Pd, Ni and P component in as-prepared catalysts. This interaction could led to a shift of the d-band center of Pd component, which may play a pivotal and dominated role in improving the catalytic performance for the ethanol electrooxidation in alkaline media.

Key words: low-doping alloy, electrocatalysts, ethanol oxidation reaction, alkaline media, enhanced performance