Abstract:

As a novel method of process intensification, microwave technology has been widely used in material preparation. The selective heating characteristic of microwave-absorbing support can lead to the formation of local overheating domains, inducing the deposition of catalyst over the support surface, which is promising to construct highly dispersed Pd-based catalysts that are crucial to improve their electrocatalytic activity and therefore promote the performance of formic acid fuel cells. With the aim to explore the feasibility of facile fabrication of highly dispersed Pd-based catalysts induced by microwave, this study first prepared microwave-absorbing ferrous phosphide (FeP) particles in the shape of hollow sea urchin using a hydrothermal method to serve as catalyst support, where Pd was deposited through ethylene glycol reduction under conventional heating and microwave heating methods, respectively. XRD, TEM, and SEM technologies were used to characterize the morphology and microstructure of Pd/FeP products, and to explore the effect of microwave heating on the dispersion of metal palladium particles on the catalyst surface. The catalytic activity of the prepared catalyst was evaluated using cyclic voltammetry and linear voltammetry. By exploring the structure-activity relationship between the structure of catalysts and their electrocatalytic activity, the strengthening mechanism of microwave synthesis on the performance of Pd/FeP catalyst was revealed. The experimental results indicate that the microwave-absorbing hollow sea urchin shaped FeP can induce the in situ deposition of Pd due to the formation of local “hot spots”, inducing the generation of highly dispersed Pd-based catalysts. Compared to traditionally prepared catalysts, the electrochemical active area of these catalysts obtained from microwave synthesis has a 3.5-fold increase, while the electrocatalytic oxidation performance of formic acid increases by about 54 times.

Key words: microwave synthesis, nanostructure, electrochemistry, catalyst, size distribution

摘要：

微波技术作为一种新型过程强化手段，已被广泛应用于材料制备过程。利用微波对吸波型载体的选择性加热，使其产生局部高温诱导催化剂颗粒的沉积，有望构筑高分散钯（Pd）催化剂结构，而这一特殊结构对提高催化剂电催化氧化甲酸活性、提升甲酸燃料电池的性能至关重要。为探究微波诱导高分散钯催化剂便捷制备的可行性，本文首先通过水热法制备了强吸波的空心海胆状磷化铁（FeP）作为催化剂载体，而后分别在常规加热与微波加热条件下通过乙二醇还原法在FeP表面沉积Pd。使用XRD、TEM、SEM技术表征Pd/FeP产品的形貌和微观结构，探究微波加热对催化剂表面金属钯颗粒分散的影响作用。使用循环伏安法和线性伏安法评价所制备催化剂的催化活性，通过探讨催化剂结构与其电催化活性的构效关系，揭示微波合成对Pd/FeP催化剂性能的强化作用机制。研究结果表明，空心海胆状的FeP颗粒具有较强的微波吸收能力，因而在受到微波辐射时，其表面形成的局部过热诱导Pd的原位沉积，使得微波水热法制备的Pd催化剂具有良好的分散特性，然而溶剂主体温度的过高会增加Pd之间的团聚。相对于常规手段合成的催化剂，利用微波水热法在120°C下制备的催化剂电化学活性面积提升了约3.5倍，对甲酸电催化氧化活性提升了约54倍。

关键词: 微波合成, 纳米结构, 电化学, 催化剂, 粒度分布