微分电化学质谱测定石墨在析氧反应中的结构腐蚀  

Characterization of Structural Corrosion of Graphite in Oxygen Evolution Reaction by Differential Electrochemical Mass Spectrometry

作　　者：刘洋[1] 卢珊珊[2] 史艳梅[2] 王雨婷 LIU Yang;LU Shan-shan;SHI Yan-mei;WANG Yu-ting(Analysis and Testing Center of Tianjin University,Tianjin 300072,China;Institute of Molecular Plus of Tianjin University,Tianjin 300072,China)

机构地区：[1]天津大学分析测试中心,天津300072 [2]天津大学分子+研究院,天津300072

出　　处：《质谱学报》2024年第4期465-471,I0001,共8页Journal of Chinese Mass Spectrometry Society

基　　金：国家自然科学基金面上项目(22275134)

摘　　要：电催化析氧反应(OER)不仅是电解水制氢的半反应,也是电催化二氧化碳还原、氮气还原、硝酸根还原、有机小分子还原、金属-空气电池的重要半反应。OER过程是通过四电子机制驱动的。由于OER自身缓慢而复杂的动力学及其自带的强氧化特性,研究电催化材料在OER中的氧化重构规律及其催化机制,对于提高析氧反应的效率意义重大。碳材料作为一类无金属电极材料广泛应用于电催化过程中,其价格低廉、储量丰富、活性、稳定性高,是一种有潜力的OER催化剂。碳材料表面的含氧官能团已被证明是OER的活性位点,但在更高的氧化电位下,由于缺乏对活性位点演化机制的认识,导致对碳材料OER性能的失活机制仍不清楚。正确识别出析氧条件下碳材料的活性位点已成为该领域的研究热点。然而,非原位的表征技术,如X射线衍射技术、扫描电子显微镜技术等难以反映碳材料在工作条件下的催化状态。因此,本文以石墨作为模型材料,利用微分电化学质谱(DEMS)探究石墨在OER过程中的结构变化,研究测试过程中外加电压和电解液pH值对石墨氧化的影响。结果表明,在酸性(pH 0)、中性(pH 7)和碱性(pH 14)条件下,高纯石墨片均是先发生自身的氧化并产生氧化官能团;随着电位的增加,酸性、中性和碱性环境中的石墨阳极均在1.6 V vs.可逆氢电极(RHE)产生CO_(2)和CO,且CO_(2)产量逐渐增大;在酸性条件下,O_(2)的生成电位高于CO_(2),而碱性条件则相反。因此,在碱性条件下,高纯石墨片在一定的电位区间下可以作为OER催化剂使用。本工作不仅揭示了碳材料在电化学氧化条件下全pH值范围内的结构转化规律和相应的演化产物,也提出了碳材料作为OER催化剂时可行的电位操作区间。Electrocatalytic oxygen evolution reaction(OER)is not only a half-reaction of water-splitting to produce hydrogen,but also an important half-reaction of electrocatalytic carbon dioxide reduction,nitrogen reduction,nitrate reduction,organic small molecule reduction,and metal-air batteries.The OER process is driven by a four-electron mechanism.Due to the slow and complex kinetics of the electrocatalytic OER and its strong oxidation characteristics,studying the oxidative reconstruction rules and catalytic mechanisms of electrode materials in the OER process is of great significance to improve the efficiency of the OER.As a kind of metal-free electrode materials,carbon materials are widely used in electrocatalysis,which has become a potential electrocatalyst for OER due to their low price,abundant reserves,and high activity stability.At present,oxygen-containing functional groups on the surface of carbon materials have been proven to be active sites for OER.However,the deactivation mechanism of carbon materials at higher oxidation potentials during the OER process remains unclear due to a lack of understanding of the active site evolution mechanism.Correctly identifying the active sites of carbon materials under oxygen evolution conditions has become a research hotspot in the field.However,ex-situ characterization techniques such as X-ray diffraction(XRD)and scanning electron microscopy(SEM)are difficult to reflect the catalytic behavior of carbon materials under working conditions.In this study,differential electrochemical mass spectrometry(DEMS)was used to monitor the structural changes of carbon material during the OER process with graphite as the model material.The effects of applied voltage and pH value of electrolyte on graphite oxidation were investigated respectively.By changing the applied potential and the pH value of the electrolyte,we found that graphite firstly oxidizes itself to form oxygen-containing functional groups under acidic(pH 0),neutral(pH 7),and alkaline(pH 14)conditions.As the potential incre

关 键 词：析氧反应(OER) 石墨 微分电化学质谱(DEMS) 结构变化 

分 类 号：O657.63[理学—分析化学]