B-N共掺杂石墨烯负载Pd基合金纳米催化剂的制备及其对甲酸电催化氧化性能的研究

Direct formic acid fuel cells (DFAFCs) system is considered to be one of the developing direction of fuel cells and is hot in recent research, because it has multiple advantages such as formic acid is non-toxic, inflammable and storage and transportation is safe, and it has higher electromotive force, lower crossover effect through the Nafion membrane, comparing with direct methanol fuel cells (DMFCs). Recently, Pd catalyst, as the most popular catalyst in direct formic acid fuel cells, has been found to show uniquely excellent catalytic activity. However, one of the disadvantages of Pd as an anodic catalyst is its instability, which is an important problem to be solved in DFAFCs. Our project aims: 1) To prepare B-N-codoped graphene (a type of new material) supported Pd alloy nanocatalyst by the improved microwave-assisted polyol method. There are two key factors: one is the role of B-N-codoped graphene as support, and the other is the role of alloy of Pd nanoparticles.The properties of Graphene will be tuned by B-N-codoping and can increase the electronic conductivity, tolerance to CO poisoning and corrosion stability of the graphene, and is designed to better disperse the Pd nanoparticles. Also, the alloyed palladium will increase the tolerance to CO poisoning and help to exhibit excellent catalytic activities for formic acid electro-oxidation; 2) To further study the effect of the preparation of the catalyst on the electro-oxidation of formic acid and to investigate the relation between the catalyst surface morphology, microstructure and electrocatalytic properties, and to reveal the catalytic mechanism for this kind of catalyst. Thus, the results can provide the theory basis for the commercial application, and then the investigation of the project will help to give an enormous impetus to the research and development of the fuel cells.

直接甲酸燃料电池（DFAFC）由于其燃料甲酸具有无毒、储运方便，理论开路电位高和Nafion膜透过率较低等优点，因而是目前燃料电池的发展方向和研究热点之一。目前最普遍的Pd催化剂具有独特优异的催化活性，但其稳定性差，是DFAFC中亟待解决的关键问题。本课题拟以新型材料B-N共掺杂石墨烯为载体，采用改进的微波多元醇法制备B-N共掺杂石墨烯负载Pd基合金纳米催化剂：通过B-N共掺杂对石墨烯进行改性，提供强导电性、抗CO毒化能力、抗酸腐蚀性和有利于附着金属Pd的载体作用；再通过金属的合金化作用提高催化剂对CO抗毒能力，以期获得成本较低、稳定性好且高催化活性的DFAFC阳极催化剂。研究催化剂表面形貌及微观结构与电催化性能的关系，揭示该催化剂的催化作用机制，并进一步阐明甲酸电催化氧化反应机理，最终为燃料电池高性能阳极催化剂的研制开发提供理论依据，有望为我国燃料电池技术的研究和开发带来一定的推动作用。

直接甲酸燃料电池(DFAFC)由于其燃料甲酸具有无毒、储运方便，比能量高和Nafion 膜透过率较低等优点，因而是目前燃料电池的研究热点之一。目前在甲酸电氧化反应体系中最普遍的 Pd 催化剂，具有独特优异的催化活性，但其稳定性差，是 DFAFC中亟待解决的关键问题。.本项目采用了水热合成法制备 B-N共掺杂石墨烯，并以其为载体制备负载 Pd及Pd金属合金纳米催化剂，应用到甲酸电催化氧化反应体系。以Pd/B-G和Pd/N-G催化剂为对比，重点考察Pd/B-N-G催化剂表面B物种、N物种的类型、比例与含量对催化剂上Pd粒子分散性和粒径大小的影响的差异，以及它们的催化剂电催化性能差异，最终揭示催化剂的催化作用机制。考察B和N元素浸渍顺序、载体的焙烧温度、不同硼源等对Pd/B-N-G催化剂的电催化性能与稳定性的影响。制备了xPdySn/B-N-G，xPdyNi/B-N-G和xPdyFe/B-N-G催化剂，以Pd/B-N-G催化剂为对比，研究金属组分对催化剂的电催化性能影响，研究了金属原子比及合金化程度对催化剂的电催化性能影响。并深入系统地探究载体和金属作用机制、催化剂作用机制和反应机理等关键科学问题。.结果发现，Pd/B-N-G催化剂的催化性能的提高，一方面由于B-N共掺杂提高了石墨烯表面吡啶N物质的比例，从而更有利于Pd分散以及Pd利用率。另一方面是B物种和N物种之间电子协同作用，对Pd产生了很强的电子作用，更多的金属态Pd提供更多的反应活性位，更低的Pd3d电子结合能，降低了Pd对CO等物种的吸附，提高催化剂抗CO中毒能力，最终提高了催化剂的催化性能。.此外，元素Ni通过形成Pd-Ni合金调变了Pd的电子结构，从而产生了协同电子效应，降低了Pd表面COOH等吸附物种的吸附能，促进HCOOH反应进行，最终提高了催化剂的催化性能。.因此我们开发获得的一系列Pd/B-N-G和PdM/B-N-G（M=Sn，Ni，Fe等）催化剂其催化活性好、抗中毒能力强、稳定性高，是一类新型阳极催化剂，其研究对于制备高性能的燃料电池催化剂和其他相关应用的催化剂都具有重要的科学意义和应用价值。也有望为我国燃料电池技术的研究和开发带来一定的推动作用。