导电共聚物衍化新策略制备硫、氮共掺杂碳纳米管及其对改善PtCu纳米晶分散性与甲醇电催化氧化的促进作用

有效调控碳纳米材料的几何和电子结构的协同效应和缺陷是获得优良电化学性能的关键.然而,如何设计一种具有优势结构的杂化材料及对其电催化机理的认识尚不清楚.本文提出了一种聚(3,4-乙撑二氧噻吩)/聚苯胺导电共聚物热解策略来制备S和N共掺杂多壁碳纳米管(MWCNTs),发现改变前驱体溶液中两种单体的比例可以调控掺杂MWCNTs中S和N原子的含量与表面活性位结构.S和N的共掺杂明显增大了碳纳米管表面的缺陷程度并暴露出更丰富的活性位点,从而有利于超细Pt和PtCu纳米颗粒的均匀分布和沉积.透射电镜和扫描透射电镜结果表明,所制备S和N共掺杂MWCNTs(SN-MWCNTs)负载的催化剂中Pt和PtCu纳米颗粒以及掺杂的S和N原子都均匀地分布在MWCNTs上,且沉积的Pt和PtCu纳米颗粒的平均尺寸仅分别为2.30和2.87 nm.X射线光电子能谱结果表明,S和N共掺杂MWCNTs与负载的Pt基纳米颗粒之间存在强烈的电荷转移相互作用,明显改变了贵金属Pt的表面电子结构.电化学测试结果表明,与Pt/SN-MWCNTs,Pt/N-MWCNTs,Pt/S-MWCNTs和商业Pt/C催化剂相比,Pt₁Cu₂/SN-MWCNTs表现出更大的电化学活性表面积(148.85 m² g^?1),更高的甲醇氧化质量活性(1589.9 mA mg_Pt^?1)、电化学稳定性和抗CO毒化能力.密度泛函理论研究表明,S和N共掺杂导致碳纳米管极大地变形,同时极化和激活了相邻的C原子.因此,增强了Pt₁Cu₂纳米颗粒在SN-MWCNTs上的吸附以及随后甲醇分子的吸附.此外,Pt₁Cu₂/SN-MWCNTs对甲醇氧化的电催化活性均在热力学和动力学上优于相应的CNTs和N-CNTs基材料.本文提供了一种新颖的在碳基材料上构建高度分散且稳定的Pt基纳米颗粒高性能燃料电池电催化剂的方法.

New strategy of S,N co-doping of conductive-copolymer-derived carbon nanotubes to effectively improve the dispersion of PtCu nanocrystals for boosting the electrocatalytic oxidation of methanol

Efficacious regulation of the geometric and electronic structures of carbon nanomaterials via the introduction of defects and their synergy is essential to achieving good electrochemical perfor-mance. However, the guidelines for designing hybrid materials with advantageous structures and the fundamental understanding of their electrocatalytic mechanisms remain unclear. Herein, super-fine Pt and PtCu nanoparticles supported by novel S,N-co-doped multi-walled CNT (MWCNTs) were prepared through the innovative pyrolysis of a poly(3,4-ethylenedioxythiophene)/polyaniline co-polymer as a source of S and N. The uniform wrapping of the copolymer around the MWCNTs pro-vides a high density of evenly distributed defects on the surface after the pyrolysis treatment, facili-tating the uniform distribution of ultrafine Pt and PtCu nanoparticles. Remarkably, the Pt1Cu2/SN-MWCNTs show an obviously larger electroactive surface area and higher mass activity, stability, and CO poisoning resistance in methanol oxidation compared to Pt/SN-MWCNTs, Pt/S-MWCNTs, Pt/N-MWCNTs, and commercial Pt/C. Density functional theory studies confirm that the co-doping of S and N considerably deforms the CNTs and polarizes the adjacent C atoms. Con-sequently, both the adsorption of Pt1Cu2 onto the SN-MWCNTs and the subsequent adsorption of methanol are enhanced; in addition, the catalytic activity of Pt1Cu2/SN-MWCNTs for methanol oxi-dation is thermodynamically and kinetically more favorable than that of its CNT and N-CNT coun-terparts. This work provides a novel method to fabricate high-performance fuel cell electrocatalysts with highly dispersed and stable Pt-based nanoparticles on a carbon substrate.