电化学石英晶体微天平研究碱性介质中单层级铂原子修饰的金电极上甲醇的电催化氧化

Electrochemical quartz crystal microbalance study on Au-supported Pt adlayers for electrocatalytic oxidation of methanol in alkaline solution

通过在Au电极表面欠电位沉积(UPD)Cu、再与Pt源(H2PtCl6或K2PtCl4)进行置换反应,制得单层级Pt原子修饰的金电极(对H2PtCl6或K2PtCl4,所制电极分别记为Pt(CuUPD-Pt4+)n/Au或Pt(CuUPD-Pt2+)n/Au,n表示欠电位沉积-置换过程的重复次数).用电化学石英晶体微天平(EQCM)技术定量研究了所制电极,评估了其在碱性环境中催化甲醇氧化的质量比活性(SECA).结果表明,以H2PtCl6为Pt源所制电极(Pt(CuUPD-Pt4+)3/Au)的活性更高,最大SECA高达35.7mAμg-1.根据EQCM结果计算了置换效率,籍此讨论了Pt原子在Au电极表面的层层组装结构,发现所制电极表面的裸Au位点分布百分数与实验结果(由AuOx还原峰电量测算)吻合.我们认为,EQCM技术是一种定量研究电极支撑的超薄催化剂的有效手段,这种高效的单层级贵金属催化剂有望在生物、能源、环境相关的电催化研究中进一步应用.

Underpotential deposition （UPD） of Cu on an Au electrode followed by redox replacement reaction of CuUPD with a Pt source （H2PtCl6 or K2PtCl4） yielded Au-supported Pt adlayers （for short,Pt（CuUPDPt4＋）n/Au for H2PtCl6,or Pt（CuUPD-Pt2＋）n/Au for K2PtCl4,where n denotes the number of UPD-redox replacement cycles）. The electrochemical quartz crystal microbalance （EQCM） technique was used for the first time to quantitatively study the fabricated electrodes and estimate their mass-normalized specific electrocatalytic activity （SECA） for methanol oxidation in alkaline solution. In comparison with Pt（CuUPD-Pt2＋）n/Au,Pt（CuUPD-Pt4＋）n/Au exhibited a higher electrocatalytic activity,and the maximum SECA was obtained to be as high as 35.7 mA μg-1 at Pt（CuUPDPt4＋）3/Au. The layer-by-layer architecture of Pt atoms on Au is briefly discussed based on the EQCM-revealed redox replacement efficiency,and the calculated distribution percentages of bare Au sites agree well with the experimental results deduced from the charge under the AuOx-reduction peaks. The EQCM is strongly recommended as an efficient technique to quantitatively examine various electrode-supported catalyst adlayers,and the highly efficient catalyst adlayers of noble metals are promising in electrocatalysis relevant to biological,energy and environmental sciences and technologies.