Institut für Physikalische Chemie, Karlsruhe Institute of Technology and University of Karlsruhe, 76131 Karlsruhe, Germany.
Chemphyschem. 2010 May 17;11(7):1416-24. doi: 10.1002/cphc.200900981.
Heat effects upon Cu deposition on polycrystalline Au surfaces from sulphuric acid electrolytes were calorimetrically measured. By combination of pyroelectric temperature detection at the backside of a thin electrode foil with pulsed electrochemistry, sensitivities to electrochemical conversions of a few percent of a Cu monolayer (ML), corresponding to about 1 microJ cm(-2) were achieved. We compared the heat evolution upon Cu under potential deposition (UPD), Cu deposition onto a fully developed Cu UPD layer and bulk Cu deposition onto a 300 ML thick Cu layer on Au. The heat effects were measured dependent on the amplitudes of the applied potential steps, that is, the driving forces of the respective reactions. From the differences of the heat effects among the Cu deposition processes, we deduced implications on the reaction mechanisms. For Cu UPD, the heat effects were explicable by the deposition of 1.3 Cu atoms per two electrons flowing to the electrode accompanied by sulphate coadsorption, similar to Cu UPD from sulphuric acid solutions on Au(111). Upon Cu deposition on a Cu UPD layer the heat effects signal considerable anion coadsorption up to the deposition of about 0.5 ML of Cu. At higher conversions the deposition mechanism gradually changes towards bulk Cu deposition, accompanied by reduction of the sulphate coverage.
从硫酸电解液中对多晶金表面上铜沉积的热效应进行了量热法测量。通过在薄电极箔的背面进行热电温度检测与脉冲电化学的组合，实现了对几%的铜单层（ML）电化学转化的灵敏度，对应约 1 微焦耳每平方厘米（μJ cm(-2)）。我们比较了在铜欠电位沉积（UPD）、在完全发展的铜 UPD 层上沉积铜以及在 Au 上沉积 300 ML 厚的铜层上沉积铜时的热释放。热效应取决于施加的电势阶跃幅度，即各自反应的驱动力。从铜沉积过程中热效应的差异中，我们推断出对反应机制的影响。对于铜 UPD，热效应可以通过每两个流向电极的电子沉积 1.3 个铜原子来解释，同时伴随着硫酸盐共吸附，类似于 Au(111)上硫酸溶液中的铜 UPD。在铜 UPD 层上沉积铜时，热效应信号表明在沉积约 0.5 ML 的铜之前存在大量阴离子共吸附。在更高的转化率下，沉积机制逐渐向块状铜沉积转变，同时硫酸盐覆盖率降低。
