富氢气体中CO优先氧化催化剂研究进展

Recent advances in noble metals and metal oxide catalysts for preferential oxidation of CO in H_2-rich stream

以高纯氢为燃料的质子交换膜燃料电池广泛应用于电动汽车,但其阳极容易被富氢气体中含有的少量CO毒化,造成电池性能严重降低。富氢气体在进入燃料电池前,必须进行CO净化处理。优先氧化法是除去富氢气体中少量CO最简单经济有效的方法,常用催化剂主要有Pt系、Au系和Cu系催化剂。着重阐述负载Au催化剂的制备方法、载体调变、助剂改性以及其他因素(如反应气氛中CO与O2浓度比、水蒸汽和CO2等)对Au催化剂CO优先氧化反应催化性能的影响。介绍以CuO/CeO2催化剂为典型的非贵金属氧化物催化剂用于CO优先氧化反应的研究成果以及制备方法、载体和助剂改性等对催化性能的影响和反相结构CeO2/CuO的催化性能。考虑利用催化剂活性组分,尤其是Au与Cu之间的协同作用,选用合适的载体,进行催化剂组分的设计仍然是今后研究的热点。突破常规无定形金属氧化物作载体,通过设计合成具有特定形貌的载体,研究不同晶面和不同价态等因素对催化剂CO优先氧化催化性能的影响,也是一项很有意义的研究。

In past decades,proton exchange membrane fuel cells （PEMFCs） with highly pure hydrogen as the fuel have been widely applied in vehicle.However,the anode of PEMFCs is prone to be poisoned by the small amounts of CO in rich hydrogen stream,leading to rapid loss of fuel cell performance.The content of CO in H2-rich stream has to be reduced to an acceptable level before the hydrogen rich gas is sent into the fuel cell.The preferential oxidation of CO （CO-PROX） in the hydrogen rich gas is considered as the simplest,the most economic and effective method to remove a small amount of CO with a minimal loss of hydrogen.There are three main catalysts,the platinum and gold based catalysts and the non-noble copperbased catalysts for CO-PROX reaction reported in literature.In this paper,the latest progress in three catalyst systems for CO-PROX were reviewed.The effects of preparation methods,the modification of carriers and additives,and the reaction atmospheres （such as the concentration ratio of CO to O2,the presence of water vapor and CO2） on the catalytic performance of supported gold catalysts were expounded in detail.As the typical non-noble metal oxide catalysts,CuO/CeO2 catalysts for CO-PROX were reviewed.The influence of preparation methods,improvement of the carriers and additives on the catalyst properties as well as the performance of the inverted structure CeO2/CuO catalyst were introduced.On the basis of analyzing the advantages and disadvantages of the three types of catalysts,considering the synergistic effect between activity components of catalysts,especially the cooperation between Au and Cu,and selecting suitable supports,it is proposed that designing a preferable catalyst for CO-PROX reaction by optimizing the catalyst composition is the research direction in the future.In addition,to design some novel carriers with specific morphologies to replace the conventional amorphous metal oxides carriers is recommended.It is meaningful to study the effects of different crystal faces and different valence states of the catalysts on their catalytic performance for CO-PROX.