焙烧氧化PdCo非预期的乙二醇电催化氧化性能的研究

Oxidative calcination of PdCo with unexpected electrocatalytic performance for ethylene glycol oxidation

钯基金属催化剂在碱性燃料电池中已有广泛的应用。然而,迄今为止,钯基金属催化剂的氧化处理对其在碱性燃料电池中应用的影响却鲜有报道。本研究通过对PdCo纳米金属催化剂的焙烧氧化处理,发现生成的PdO-Co_(3)O_(4)纳米复合材料在碱性溶液中对乙二醇电催化氧化的质量比活性和面积比活性分别是商业Pt/C的3.8和2.4倍。与PdCo纳米金属相比,PdO-Co_(3)O_(4)纳米复合材料在碱性溶液中对乙二醇电催化氧化的质量比活性和面积比活性分别提高了1.6和1.2倍。实验和计算结果表明,焙烧氧化处理改变了催化剂的表面形态和活性中心,在Co掺杂PdO(101)表面上,O_(2)和OH吸附能降低,有利于稳定中间体C_(2)H_(4)OHO*和O−H解离,Co掺杂纳米级PdO(101)与乙二醇及其中间物种发生强烈的结合,导致形成不同的电化学动力学和反应路径,从而产生优良的电催化活性。PdO和Co_(3)O_(4)的协同作用明显增强了活性氧与催化剂表面之间的相互作用,不仅有利于超氧物种在催化剂表面上的形成,而且提高了催化剂的氧化还原性质,促进乙二醇的电催化氧化活性。本文提出的双/多金属氧化策略为构建其他催化剂提供了一个通用的方法。

Pd-based catalysts have been widely used in alkaline fuel cells.However,up to now,the effects of oxidation treatment of Pd-based catalysts on their application in alkaline fuel cells have been rarely reported.In this paper,PdCo nano-metal catalyst was prepared by calcination-oxidation treatment.It was found that the mass specific activity and area specific activity of the resulting PdO-Co_(3)O_(4)nano-composite for electrocatalytic oxidation of ethylene glycol in alkaline solution were 3.8 and 2.4 times that of commercial Pt/C,respectively.Compared with PdCo nanometals,the mass specific activity and area specific activity of the PdO-Co_(3)O_(4)nanocomposite for the electrocatalytic oxidation of ethylene glycol in the alkaline solution increased by 1.6 and 1.2 times,respectively.The experimental and calculated results showed that the surface morphology and active center of the catalyst changed after calcination and oxidation treatment.The adsorption energies of O_(2)and OH on the Co doped PdO(101)surface decreased,which was beneficial to stabilize the intermediate C_(2)H_(4)OHO*.As a result,the energy barrier for the O−H dissociation on the Co-doped surface was reduced.The strong binding of Co doped PdO(101)with ethylene glycol and its intermediate species led to different electrochemical kinetics and reaction path to produce excellent electric catalytic activity.The synergistic effect of PdO and Co_(3)O_(4)significantly enhanced the interaction between active oxygen and catalyst surface,which not only facilitates the formation of superoxide species on the catalyst surface,but also improves the redox properties of the catalyst and promotes the electrocatalytic oxidation activity of ethylene glycol.The strategy of bi/multi-metallic oxidation proposed in this paper provides a general methodology for the construction of other catalysts.