自由基参与纳米铂基金属表面氰化重构及其抗“甲醇渗透”电催化性能

Nanostructured Pt-based materials have been widely used as cathode electrocatalysts for oxygen reduction reactions (ORR) in direct methanol fuel cells (DMFCs). However, the poor durability of Pt-based electrocatalysts caused by methanol (MeOH) crossover from anode to cathode is currently one of the most crucial technical challenges that impedes the commercialization of DMFCs. In order to tailor the selectivity and stability of Pt-based electrocatalysts, molecular surface engineering procedures have emerged as powerful tools in recent years. In this proposal, we present a cyanide radical patterning strategy to modify Pt-based electrocatalysts using a simple and green Fenton reaction (normal Fenton and photo-Fenton processes) induced surface cyanation technique. By controlling the reaction time or reaction routes, it is easy to tune the surface cyanation level of Pt catalysts. More importantly, the resulting special topological structure constructed by the cyanide groups enables a stable ORR reactivity as well as enhanced methanol-tolerant ability of Pt electrocatalysts operated in alkaline media. We will employ DFT calculations and spectroscopic analysis to understand the hidden reaction mechanism behind the surface reconstructed Pt-based metal nanocatalysts with cyanide radicals. It is expected that the outcome of this proposal will have immediate practical implications and advantages for commercial applications of DMFCs where Pt-based electrocatalysts are used as cathode materials.

直接甲醇燃料电池（DMFC）有望成为未来便携式电子产品应用的主流，然而现阶段难以被其它催化材料替代的阴极Pt基催化剂仍存在着诸多问题。目前，如何提高纳米Pt基材料的反应活性和稳定性以及增强其抗“甲醇渗透”性能是DMFC工业应用取得突破的关键因素之一。在该项目中，申请人拟利用近期发展的绿色芬顿氰化法和光化学氰化法对预合成的负载型Pt基纳米金属进行自由基参与表面原位氰化重构改性。通过控制反应时间或反应路径，我们可以简单地调控纳米Pt的表面氰化程度，构造出所需的特殊表面拓扑结构，产生表面几何效应，从而对催化剂的选择性和反应活性进行有效调控。基于电催化测试结果，申请人将深入研究氰化重构Pt基纳米金属电极的氧还原活性增效机制，并结合光谱学和DFT理论计算从分子层面阐明表面氰基拓扑结构抑制甲醇等小分子中毒的微观机理。该项目的顺利开展有望为我们提供一条全新的技术路径来提高Pt基催化剂的活性和稳定性。

本项目按照计划制备了一系列基于纳米金属颗粒的负载型催化材料，并通过我们近期开发的绿色自由基氰化法，对材料表面进行光化学可控氰化改性，构建有机/无机杂化的特殊表面拓扑结构，在增进ORR电催化活性的同时，还能抑制甲醇和CO等小分子中毒现象。结合光谱学和DFT理论计算结果，我们阐明了光化学氰基改性机理、ORR催化活性增效机制以及表面氰基几何效应对抑制甲醇渗透和CO中毒的微观机理，为构筑新一代抗甲醇渗透DMFC产品积累了基础研究数据。此外，我们还将研究拓展到了非碱性介质中低温催化甲醛溶液重整制氢（HER）的新型催化体系。研究发现纳米金属负载MgO催化醛类分子的HER过程由氧气控制，这一现象打破了传统催化制氢理论，即氧气的存在会抑制产氢效率的观点，证实了氧气也可以作为一种催化剂实现快速产氢的目标。由此，我们发现了一类全新的表界面改性催化体系，不仅在电催化方面有一定的应用前景，在热催化和光催化方面也打开了一扇窗。