Maher Robert C, Shearing Paul R, Brightman Edward, Brett Dan J L, Brandon Nigel P, Cohen Lesley F
The Blackett Laboratory, Imperial College London Prince Consort Road London SW7 2BZ UK.
The Electrochemical Innovation Lab Department of Chemical Engineering University College London Torrington Place London WC1E 7JE UK.
Adv Sci (Weinh). 2015 Sep 25;3(1):1500146. doi: 10.1002/advs.201500146. eCollection 2016 Jan.
The redox properties of gadolinium doped ceria (CGO) and nickel oxide (NiO) composite cermets underpin the operation of solid oxide electrochemical cells. Although these systems have been widely studied, a full comprehension of the reaction dynamics at the interface of these materials is lacking. Here, in situ Raman spectroscopic monitoring of the redox cycle is used to investigate the interplay between the dynamic and competing processes of hydrogen spillover and water dissociation on the doped ceria surface. In order to elucidate these mechanisms, the redox process in pure CGO and NiO is studied when exposed to wet and dry hydrogen and is compared to the cermet behavior. In dry hydrogen, CGO reduces relatively rapidly via a series of intermediate phases, while NiO reduces via a single-step process. In wet reducing atmospheres, however, the oxidation state of pure CGO is initially stabilized due to the dissociation of water by reduced Ce(III) and subsequent incorporation of oxygen into the structure. In the reduction process involving the composite cermet, the close proximity of the NiO improves the efficiency and speed of the composite reduction process. Although NiO is already incorporated into working cells, these observations suggest direct routes to further improve cell performance.
钆掺杂二氧化铈（CGO）和氧化镍（NiO）复合金属陶瓷的氧化还原特性是固体氧化物电化学电池运行的基础。尽管这些体系已得到广泛研究，但仍缺乏对这些材料界面处反应动力学的全面理解。在此，利用原位拉曼光谱对氧化还原循环进行监测，以研究掺杂二氧化铈表面上氢溢流和水离解这两个动态且相互竞争的过程之间的相互作用。为了阐明这些机制，研究了纯CGO和NiO在暴露于湿氢和干氢时的氧化还原过程，并与复合金属陶瓷的行为进行比较。在干氢中，CGO通过一系列中间相相对快速地还原，而NiO通过单步过程还原。然而，在湿还原气氛中，由于还原的Ce(III)使水离解并随后将氧掺入结构中，纯CGO的氧化态最初得以稳定。在涉及复合金属陶瓷的还原过程中，NiO的紧密存在提高了复合还原过程的效率和速度。尽管NiO已被用于工作电池中，但这些观察结果为进一步提高电池性能指明了直接途径。
