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

Underpotential deposition(UPD) of Cu on an Au electrode followed by redox replacement reaction(RRR) of CuUPD with a Pt source(H2PtCl6 or K2PtCl4) yielded Au-supported Pt adlayers(for short,Pt(CuUPD-Pt4+)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 ?g?1 at Pt(CuUPD-Pt4+)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 with the experimental results deduced from the charge under the AuOx-reduction peaks.The EQCM is highly 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.