铂族金属催化剂低温CO氧化研究近期进展（英文）

发布时间：2018-06-15 06:18

  本文选题：一氧化碳氧化 + 金　； 参考：《催化学报》2016年11期

【摘要】：CO氧化可能是多相催化领域最常见的反应,它不仅能作为探针反应研究催化剂结构、反应活性位等,而且在诸多实际过程如空气净化、汽车尾气污染物控制、燃料电池所用氢源净化等扮演重要角色.最早的CO氧化催化剂为霍加拉特剂,其组分主要为CuO与Mn O_2混合氧化物,然而在实际应用过程中存在低温活性低、吸湿易失活等缺点.1987年,Haruta等发现湿化学法制备的氧化物负载Au催化剂表现出非常高的低温CO氧化活性及耐水稳定性,其Au粒子以纳米尺度分散,进而引发了催化研究领域的"淘金热"及纳米催化研究热潮.而CO氧化通常作为考察Au催化剂结构性质的探针反应,也成为考核其它金属催化剂是否具有高活性的判据之一.Pt族金属上CO氧化反应从Langmuir等研究开始至今已有100多年,然而低温下该金属催化剂活性与Au催化剂相比要低一个数量级.本质原因为Pt族金属上CO吸附较强,O_2吸附与活化受到抑制,而该步骤被认为是CO氧化的速控步,因而表现出较低的催化活性.通常Pt族金属催化剂需要100 oC以上CO才能脱附,O_2进而得以吸附.目前研究人员采取多种策略,其基本原则为削弱Pt族金属上CO吸附强度或者提供其它活性位供O_2吸附与活化.本综述将概括近十年来Pt族金属催化剂CO氧化研究进展,主要总结室温甚至超低温条件下的研究成果.高活性CO氧化催化剂主要是通过采用可还原氧化物为载体或助剂,或者改变催化剂表面性质如使表面富OH基物种来形成.Au催化剂的研究发现,改变金属粒子尺寸极有可能获得不同寻常的催化性能,而常规的Pt族金属催化剂研究主要是在纳米尺度.近期人们发现逐渐减小Pt族金属粒子尺寸,从纳米到亚纳米甚至单原子时,其电荷状态逐渐呈正价形式,这有利于削弱其CO吸附强度.此外,可通过增强金属载体间的相互作用,改变金属载体接触方式,如从核壳到交叉结联结构,构筑出更多的金属载体界面,使得O_2更容易吸附与活化或稳定更多的OH基物种进而在此界面与吸附的CO反应.伴随着表征技术的发展,CO氧化机理的认识也更加深入,这给催化剂的设计带来更多新的思路.(1)改变CO吸附活化位,将CO吸附活化位从金属转移到载体上,从而大大降低CO吸附强度,活化的CO物种在反应过程中容易溢流到金属载体界面处,这甚至有利于超低温度下( 100℃左右)CO氧化.(2)改变O_2活化形式.O_2通常在Pt族金属上容易以解离氧原子形式存在,通过改变载体、金属载体界面性质使得O_2以分子氧形式活化,如形成超氧或过氧物种,这有利于降低CO氧化的活化能垒,进而提高其低温甚至超低温下CO氧化活性.今后,设计并合成出在超低温度下能够氧化CO的Pt族金属催化剂将成为CO氧化催化剂研究的重要方向之一.
[Abstract]:Co oxidation is probably the most common reaction in the field of heterogeneous catalysis. It can not only be used as a probe to study catalyst structure and reactive sites, but also in many practical processes such as air purification and vehicle exhaust pollutant control. Hydrogen purification used in fuel cells plays an important role. The earliest catalyst for CO oxidation was Hogarat, the main component of which was CuO and MNO _ 2 mixed oxides. However, the low temperature activity was found in the practical application of CuO and MNO _ 2 mixed oxides. In 1987, Haruta et al found that the oxide supported au catalysts prepared by wet chemical method showed very high CO oxidation activity at low temperature and water resistance stability, and their au particles were dispersed in nanometer scale. This led to the gold rush and nano-catalysis research in the field of catalytic research. Co oxidation is usually used as a probe reaction to investigate the structure and properties of au catalysts. Co oxidation on Pt group metals has been studied for more than 100 years since Langmuir and so on. However, the activity of the metal catalyst at low temperature is one order of magnitude lower than that of au catalyst. The essential reason is that the adsorption and activation of CO on Pt group metals are inhibited, and this step is considered to be the rapid control step of CO oxidation, so it shows low catalytic activity. Usually Pt group metal catalysts require more than 100oC of CO to desorb O _ s _ 2 and then to be adsorbed. At present, researchers have adopted a variety of strategies, the basic principle of which is to reduce the adsorption strength of CO on Pt group metals or to provide other active sites for adsorption and activation of O _ (2). This review will summarize the progress in CO oxidation of Pt group metal catalysts in recent ten years, especially at room temperature and even at very low temperature. High activity CO oxidation catalyst is mainly found by using reductive oxide as carrier or auxiliary, or changing the surface properties of catalyst such as making the surface of the catalyst rich in OH group species to form .au catalyst. It is very possible to obtain unusual catalytic properties by changing the size of metal particles, while conventional Pt group metal catalysts are mainly studied at nanometer scale. Recently, it has been found that when the size of Pt group metal particles is gradually reduced, the charge state of Pt group metal particles is gradually in the form of positive valence from nanometer-sized to sub-nanoscale or even monoatomic, which is beneficial to weaken the adsorption intensity of CO. In addition, more metal carrier interfaces can be constructed by enhancing the interaction between metal carriers and changing the contact modes of metal carriers, such as from core-shell to cross-junction structures. It makes it easier for O _ s _ 2 to adsorb and activate or stabilize more OH group species and then react with adsorbed CO at this interface. With the development of characterization technology, the mechanism of CO oxidation is more deeply understood, which brings more new ideas to the design of catalyst. As a result, the adsorption intensity of CO is greatly reduced, and the activated CO species can easily overflow to the interface of the metal carrier during the reaction. This even helps to change the activation form of O _ (2) at ultra-low temperature (about 100 鈩，

本文编号：2021007