Ag2-xO with highly exposed{111}crystal facets for efficient electrochemical oxygen evolution:Activity and mechanism  

高暴露{111}晶面Ag2-xO用于高效电化学析氧反应及其活性和机理

作　　者：Xiao-Feng Zhang Jian-Sheng Li Wan-Sheng You Zai-Ming Zhu 张晓枫;李健生;由万胜;朱再明(辽宁师范大学化学化工学院,辽宁大连116029)

机构地区：[1]School of Chemistry and Chemical Engineering,Liaoning Normal University,Dalian 116029,Liaoning,China

出　　处：《Chinese Journal of Catalysis》2020年第11期1706-1714,共9页催化学报（英文）

基　　金：国家自然科学基金(21573099,21601077);多酸科学教育部重点实验室开放项目.

摘　　要：A series of Ag2–xO/FTO-i electrodes(where i denotes the current density during the electrodeposition, and i = 0.5, 1, 2, 3, 4, or 7) was fabricated in 0.1 M K2B4O7 electrolyte containing Ag+ ions by galvanostatic electrocrystallization. The electrode composition and morphology were characterized using X-ray powder diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The results reveal that the electrode films consist of Ag2O, but some of the Ag+ ions on the {111} crystal facets are oxidized into Ag2+ ions. Furthermore, the Ag2–xO/FTO-1 electrode shows a triangular slice shape of a parallel matrix with a larger exposed area of {111} crystal facets than other Ag2–xO/FTO-i(i = 0.5, 2, 3, 4, or 7) electrodes. Electrocatalytic experiments prove that the Ag2–xO/FTO-1 electrode produces the highest oxidative current density, has an overpotential of 417 m V at 10 m A cm–2, and has a Tafel slope of 47 m V dec–1 in 0.1 M K2B4O7. Electrochemical impedance spectra indicate that Ag2–xO/FTO-1 electrodes have the best ability for charge transfer. In addition, in the I-t test over 10 h, the current density decreased 4%. Fortunately, both O–O and Ag2+ species were detected after electrocatalysis and a possible mechanism for the oxygen evolution reaction is proposed in which the formation of Ag2+ and O–O species on {111} facets plays a critical role.析氧反应(OER)是工业上制约水裂解制氢和CO2综合利用的瓶颈,涉及四电子、四质子耦合以及O-O键的形成,是一个复杂的、高活化能(高过电位)的动力学过程.模拟自然界光系统PS Ⅱ,发展高效、稳定、经济的析氧催化剂(OEC)是一个具有挑战性的研究课题.Ag基催化剂因具有以下优势而成为候选:(1)Ag与Ru同属第五周期性质相近,且有经济性且储量丰富;(2) Ag比第三周期过渡金属具有更高的电子密度和更多可调节配位数;(3) Ag存在Ⅰ, Ⅱ, Ⅲ多种氧化态.本课题组前期工作证明, Ag基配合物[H3AgI(H2O)PW11O39]3–在酸性水溶液体系中能够形成高氧化态AgⅡ和AgⅢ配合物,用于OER时展现出高活性和稳定性.受此启发,我们选择简单银基氧化物用于研究电催化OER活性并探究其催化机理.本文通过恒电流沉积法在含有Ag+离子的0.1 M K2B4O7电解质溶液中设计合成了系列Ag2–xO/FTO-i (i=0.5, 1, 2, 3, 4, 7m Acm–2)电极,并通过XRD, SEM和TEM方法对其组成和形貌进行了表征.XRD结果表明,电极膜由Ag2O组成,随着沉积电流密度增加,其{111}晶面衍射峰向高角度移动,推测是由部分Ag+离子氧化成Ag2+离子所致.SEM显示, Ag2–xO/FTO-1电极膜上Ag2–xO主体呈现三角薄片状,拥有比其它电极Ag2–xO/FTO-i(i=0.5,2,3,4,7)暴露更多的{111}晶面.同时,高倍TEM显示晶面间距为0.267 nm,进一步证明存在较多暴露{111}晶面.线性扫描伏安曲线(LSV)显示, Ag2–xO/FTO-1电极具有最高的OER电流密度,通过对Tafel区域进行拟合,得到Tafel方程η=0.37+0.047 log|j|,计算得出在10 m A cm–2电流密度下Ag2–xO/FTO-1电极具有较低的Tafel斜率47 m Vdec–1和过电位417 m Vvs.RHE,可用作高效的OEC.电化学阻抗谱(EIS)表明,相比其它电极, Ag2–xO/FTO-1具有最佳的电荷转移能力.电流–时间(I–t)曲线显示10h内其电流密度仅下降4%,表明电极稳定性良好.通过XPS和拉曼光谱发现, Ag2–xO/FTO-1经过循�

关 键 词：AG2O Crystal facet Ag2+ions ELECTROCATALYSIS Water oxidation Oxygen evolution reaction 

分 类 号：TQ116.2[化学工程—无机化工] TQ426