CNTs孔结构中SnO2表面晶核诱导电沉积制备DAFCs高Pt利用率阳极催化剂

The lower utilization, activity and stability of noble metal catalysts are the common issues faced by direct alcohol fuel cells. Due to the fact that porous structure favors mass transfer and catalyst utilization, and SnO2 is a corrosion-resistant and co-catalytic support, and electro-deposition can improve catalyst utilization, porous CNT-based structure is formed using pore-forming agents and on CNTs are loaded SnO2 as supports. On SnO2 there lie nuclei of Pt, Au or Pd that can induce electro-deposition of Pt and Au on SnO2, resulting with porous catalysts layer of Pt/SnO2/CNTs and Au/SnO2/CNTs. Au@Pt/SnO2/CNTs and Au@PtRh/SnO2/CNTs are prepared employing electro-deposition on Au/SnO2/CNTs. To achieve the facile regulation of electro-deposition, the effects of electro-deposition conditions are investigated on sizes, morphologies, composition and electrochemical active specific surface area of Pt catalysts. Catalysts series are prepared for structural characterization and the electrochemical methods are used to study the utilization, activity and stability of catalysts and the mass transfer properties of catalysts layer, the structure-performance relationship being analyzed based upon the above results. Finally the direct ethanol fuel cells are assembled for comprehensive performance evaluation. This study is meaningful for improving catalysts performance and expediting DMFC commercialization,and can boost theoretical development in electrodeposition regulation and application guidance.

直接醇燃料电池(DAFCs)存在贵金属催化剂利用率低、活性及稳定性不高问题。鉴于孔结构利于催化层传质和催化剂利用，SnO2有耐蚀性和助催化作用，电沉积可提高催化剂利用率，故用载有SnO2的碳纳米管CNTs和造孔剂构筑孔结构，利用SnO2表面Pt、Au和Pd核诱导，将Pt和Au选择性电沉积在SnO2表面，制得Pt/SnO2/CNTs和Au/SnO2/CNTs，在Au/SnO2/CNTs基础上继续电沉积可制备Au@Pt/SnO2/CNTs和Au@PtRh/SnO2/CNTs。通过考察电沉积条件对催化剂粒径、形貌、组成、电化学活性面积等影响，掌握电沉积调控规律；对系列催化剂进行结构表征，并考察催化剂利用率、活性、稳定性和催化层传质特性，分析催化剂结构与性能关系并组装电池评价性能。该研究对提高催化剂性能和加快DMFC市场化进程有实际价值，对探索电沉积调控规律和拓展电沉积应用有积极理论意义。

直接液体燃料电池阳极催化剂以贵金属Pt和Pd为主要催化组分，尚存在贵金属利用率、活性及稳定性有待提高等问题。因电沉积可提高催化剂利用率，本项目首先探索了在Au基底表面电沉积Pt及Pd以提高利用率及催化活性等，进一步探索了催化剂结构与性能关系，并初步研究了载体特性对催化剂抗毒性影响。(1)利用SnO2表面Au核诱导，将催化剂选择性电沉积在SnO2表面Au核上，制得复合催化剂Pt-on-Au/SnO2/CNTs。催化剂对碱性体系甲醇电氧化具有优异催化性能(最高质量活性约220 A mgPt-1)，解释了Au与Pt之间的协调催化作用，为催化剂设计提供了新思路。进一步制备了Pd-on-Au和Pt-on-Pd-on-Au催化剂，改善了Pt的稳定性。(2)通过考察甲醇和乙醇在不同表面组成Pt-on-Pd系列催化剂上电氧化活性及稳定性，发现Pt对甲醇及乙醇电氧化催化活性均优于Pd但乙醇在Pt上活性衰减较快。分析原因认为，乙醇电氧化中间产物在Pt上缩聚引起Pt活性降低，因此乙醇电氧化宜选择Pd基催化剂而甲醇电氧化宜选择Pt基催化剂。(3)利用原子层沉积技术制备了Pd-on-Ag系列催化剂，发现其Pd利用率及对甲酸盐电氧化抗毒性均优于Pd催化剂。这归因于Ag基底对Pd组分的电子调节作用，为甲酸盐电氧化催化剂结构设计提供研究基础。(4)将Pt分别载于碳纳米管与石墨烯上制得催化剂Pt/CNTs和Pt/GNs用于甲酸盐电氧化，多种评价指标一致表明Pt/GNs抗毒性显著优于Pt/CNTs，这可归因于石墨烯表面较多缺陷位与Pt的强相互作用。进一步以CNTs为基础制得缺陷程度/官能团特性不同的系列载体负载Pt用于甲酸盐电氧化。抗毒性分析表明，缺陷程度越大，则Pt与载体间相互作用越大，Pt抗毒性越好。该结果为从载体角度改善催化剂抗毒性提供了新思路。总之，该项目为改善催化剂利用率、活性、稳定性及抗毒性等，创新了制备方法，揭示了构效关系，初步探索了载体特性对催化剂抗毒性影响规律。实现了预期研究目标，拓展了研究内容，具有较强创新性。