PdCoIr四面体合金纳米催化剂的制备及其对乙醇氧化的电催化性能

钯(Pd)基催化剂是直接乙醇燃料电池研究中广泛使用的催化剂,进一步提升其性能是推动燃料电池发展的重要方向.本文用一步水热法制备出四面体结构PdCo(PdCo tetrahedron,记为PdCo-TH)和少量铱(Ir)掺杂的PdCo四面体合金纳米粒子(记为PdCoIr-TH).经TEM、ICP、XPS 及CV 等表征证...

Preparation of PdCoIr Tetrahedron Nanocatalysts and Its Performance toward Ethanol Oxidation Reaction

As a new energy conversion device, direct ethanol fuel cells (DEFCs) are widely concerned because of their remarkable advantages such as high theoretical energy density and wide fuel sources. However, the rapid development of DEFCs has been severely impeded due to the sluggish kinetic process and toxic intermediates especially in their anodic reactions. Palladium (Pd)-based materials are considered to be excellent anode catalysts for DEFCs, especially under alkaline conditions. And further improving their performance is an important direction to promote the development of DEFCs. Surface structure and composition are the key factors affecting the performance of catalysts which can be improved by reasonable regulation. It is reported that high-index faceted structures and element doping are beneficial to improve the performance of catalyst. In this work, the advantages of these two strategies were used comprehensively to prepare Pd-based catalysts with high efficiency. Palladium cobalt (PdCo) and Ir-doped PdCo tetrahedron alloy nanocatalysts (denoted by PdCo-TH and PdCoIr-TH, respectively) have been successfully prepared by one-step hydrothermal method. The characterization results of TEM, ICP, XPS and CV show that the PdCo-TH binary and PdCoIr-TH ternary alloys were formed, while Ir element was mainly distributed on the PdCoIr-TH surface. Compared with the commercial Pd/C, the PdCo-TH/C and PdCoIr-TH/C exhibited the enhanced catalytic properties toward ethanol oxidation reaction in alkaline solutions. Particularly, the Pd₉Co₁Ir_0.1-TH/C catalyst showed the best activity and stability toward EOR, especially at low potentials (< -0.25 V). And Ir sites not only resisted CO poison effectively, but also shifted the initial oxidation potential of ethanol negatively. Meanwhile, the selectivity of C1 products during the electrocatalytic oxidation of ethanol has been greatly improved with the increase of Ir content. The enhanced reactivities of PdCo-TH/C and PdCoIr-TH/C could be attributed to: (a) The coexistence of Co sites and Ir sites on the surfaces can generate OH_ad species which can promote the oxidation of intermediate adsorbed species on Pd sites and (b) the negative shift in electron binding energy of Pd due to the addition of Ir may make reaction intermediates desorb more difficultly, which might make the reactivity of PdCoIr-TH/C differ from that of PdCo-TH/C. This research work has demostrated a strategic approach for future development in high efficiency catalysts used for DEFCs.