摘要
The development of highly efficient and cost-effective electrode materials for catalyzing the oxygen evolution reaction(OER)is crucial for water splitting technology.The increase in the number of active sites by tuning the morphology and structure and the enhancement of the reactivity of active sites by the incorporation of other components are the two main strategies for the enhancement of their catalytic performance.In this study,by combining these two strategies,a unique three-dimensional nanoporous Fe-Co oxyhydroxide layer coated on the carbon cloth(3D-FeCoOOH/CC)was successfully synthesized by in situ electro-oxidation methods,and directly used as a working electrode.The electrode,3D-FeCoOOH/CC,was obtained by the Fe doping process in(NH4)2Fe(SO4)2,followed by continuous in situ electro-oxidization in alkaline medium of“micro go chess piece”arrays on the carbon cloth(MCPAs/CC).Micro characterizations illustrated that the go pieces of MCPAs/CC were completely converted into a thin conformal coating on the carbon cloth fibers.The electrochemical test results showed that the as-synthesized 3D-FeCoOOH/CC exhibited enhanced activity for OER with a low overpotential of 259 mV,at a current density of 10 mA cm^–2,and a small Tafel slope of 34.9 mV dec^–1,as well as superior stability in 1.0 mol L^–1 KOH solution.The extensive analysis revealed that the improved electrochemical surface area,conductivity,Fe-Co bimetallic composition,and the unique 3D porous structure together contributed to the enhanced OER activity of 3D-FeCoOOH/CC.Furthermore,the synthetic strategy applied in this study could be extended to fabricate a series of Co-based electrode materials with the dopant of other transition elements.
开发高效、廉价的电极材料应用于电催化氧析出反应(OER)在水分解技术中起着至关重要的作用.提高催化剂催化活性的策略主要有两种,一是通过调整催化剂形貌和结构来增加催化活性位点数量,二是通过掺入其它组分来增强催化活性位点的反应活性.本工作结合这两种策略,通过原位电氧化方法成功合成了生长在碳布上具有独特三维结构的纳米多孔铁钴羟基氧化物(3D-FeCoOOH/CC),合成的电极材料直接用作电催化析氧反应的工作电极.以生长在碳布上的“微型棋子”阵列(MCPAs/CC)作为前驱体,先后通过在(NH4)2Fe(SO4)2溶液中进行Fe掺杂工艺和在碱性介质中原位电化学氧化制备了3D-FeCoOOH/CC.微观表征表明,MCPAs/CC上的“微型棋子”阵列完全转化为一层薄形涂层包覆在碳布纤维上.电化学测试结果表明,合成的3D-FeCoOOH/CC在1.0 mol L^-1 KOH溶液中表现出优异的OER催化活性,在电流密度为10 mA cm^-2时所需的过电势仅为259 mV,塔菲尔斜率为34.9 mV dec^-1,并且具有优异的稳定性.详细的表征表明,电化学表面积的增加、电导率的增高、FeCo双金属组成和独特的3D多孔结构共同使得3D-FeCoOOH/CC的催化OER活性增强.此外,本实验所应用的合成策略可以扩展到制备一系列其他过渡元素掺杂的Co基电极材料.利用选区电子衍射、红外光谱和XPS等技术证明了双金属羟基氧化物的合成.从扫描电子显微镜图和透射电子显微镜图可以看出,本实验所合成的3D-FeCoOOH/CC具有多孔结构,相应的元素分布图表明Fe和Co元素在催化剂中均匀分布.N2吸脱附测试进一步证明了多孔结构的生成.XPS测试结果表明,前驱体中Co元素为+2价,3D-CoOOH/CC中的Co元素为+3价,Co 2p电子结合能分别为780.5和795.7 eV,当将Fe引入其中时,3D-FeCoOOH/CC中的Co元素也为+3价,但Co 2p电子结合能变为780.9和796.1 eV.相比于3D-CoOOH/CC,3D-FeCoOOH/CC中Co元素的电子结合能增加了0.4 eV,这表明Fe的引入调节了Co原子的电子结构,并且Fe原子和Co原子之间存在强烈的相互作用.3D-FeCoOOH/CC在~785 eV处增强的Co的伴随峰表明Co原子的简并轨道被破坏引起Co 3d电子群重排,而Co 3d电子群的重排导致Co原子电子密度增加,有利于催化活性的增强.此外Fe元素的加入可以调节OH在催化剂上的吸附,从而增强催化活性.3D-FeCoOOH/CC表现出优异的电催化析氧性能,可以归因于以下几方面:首先,Fe元素掺入提高电极材料的电化学活性面积(ECSA)、电导率和质量传递;其次,Co与掺杂Fe之间的强烈相互作用调节了电子密度和OH在催化剂表面吸附;第三,3D-FeCoOOH/CC独特的3D多孔结构具有较大的表面积,有利于催化活性位点的暴露、电解质与催化剂的接触和产生氧气的释放;第四,独特的3D多孔电极材料具有良好的结构稳定性,从而使3D-FeCoOOH/CC具有更好的稳定性.得益于上述优势,本实验所合成的3D-FeCoOOH/CC电极表现出优异的电催化析氧性能.
基金
supported by the Taishan Scholar Program of Shandong (ts201511027)
the Natural Science Foundation of Shandong Province (2018GGX102030)
support from the “Hundred Talent Program” of Chinese academy of Sciences (CAS) (RENZI[2015] 70HAO, Y5100619AM),DICP and QIBEBT (UN201804),Dalian National Laboratory For Clean Energy (DNL),CAS
Research Innovation Fund (QIBEBT SZ201801)~~
