离子液体阳离子特性对铂基氧还原电催化剂性能的影响

Effect of cationic properties of ionic liquids on the performance of platinum-based oxygen reduction electrocatalysts

离子液体(ILs)改性固体催化剂是一种构筑高效电催化界面的方法。为了研究ILs阳离子在催化剂中Pt表面对燃料电池中氧还原反应(ORR)性能的影响,本研究自主合成了两种疏水质子型ILs ([EIM][NTf_(2)],[BIM][NTf_(2)])和两种疏水非质子型ILs([EMIM][NTf_(2)],[BMIM][NTf_(2)]),并对商业化Pt/C进行改性。在本研究采用的咪唑类疏水ILs中,质子型ILs改性催化剂的ORR活性均高于非质子型ILs改性催化剂,其中,由1-丁基咪唑双(三氟甲磺酰)亚胺改性后的催化剂([BIM][NTf_(2)]@Pt/C)活性最高。在酸性半电池中ORR半波电位高达0.913 V (vs.RHE),质量活性提升至商业化Pt/C的1.73倍,比活性提升至商业化Pt/C的3倍,同时达到5000圈循环后半波电位仅下降12 mV,性能仍高于商业化Pt/C。进一步材料表征和电化学测试表明,[BIM][NTf_(2)]@Pt/C电催化活性的增强归因于该ILs可增多Pt表面参与反应活性位点、强化Pt表面质子及质量传递,并可有效抑制Pt纳米颗粒溶解,从而起到了增强ORR活性及稳定性的作用。本研究深化了对ILs@Pt界面协同电催化机理的认识,为设计下一代高效燃料电池催化剂提供了理论依据。

Ionic liquids(ILs) modified solid catalysts are considered to be an effective method for constructing efficient electrocatalytic interface.In order to investigate the cationic impacts of ILs on Pt surface towards the oxygen reduction reaction(ORR) performance,herein we selected and synthesized [NTf_2]-based two hydrophobic protonic ILs([EIM] [NTf_2],[BIM] [NTf_2]) and two hydrophobic non-protonic ILs([EMIM] [NTf_2],[BMIM][NTf_2]),and the synthesized ILs were used to modify the commercial Pt/C catalyst surface.Among the imidazoliumbased hydrophobic ILs used in this study,the ORR activities of the protonic ILs modified catalysts were all higher than those of the non-protonic ILs modified catalysts,with the catalyst modified by 1-butylimidazolium bis(trifluoromethanesulfonyl)imide([BIM] [NTf_2]@Pt/C) having the highest activity.The ORR half-wave potential in the acidic half-cell is as high as 0.913 V(vs.RHE),increasing the mass activity to 1.73 times than that of commercial Pt/C and the specific activity to 3 times than that of commercial Pt/C,while reaching a half-wave potential drop of only 12 mV after 5000 cycles,the performance is still higher than that of commercial Pt/C.Further material characterization and electrochemical tests were performed on the catalysts showed that the enhanced electrocatalytic activity of [BIM][NTf_2]@Pt/C was attributed to the increased number of active sites on the Pt surface from the ILs modification,which enhanced plasmon and mass transfer on the Pt surface,and effective inhibition of Pt nanoparticle solubilization,thus enhancing the ORR activity and stability.This study deepens the understanding of the synergistic electrocatalytic mechanism at the ILs@Pt interface and provides a theoretical basis for the design of next-generation high-efficiency fuel cell catalysts.