本文研究了金电极上吸附对氨基苯硫酚（PATP）的电化学行为。在0.05 mol·L^-1的硫酸溶液（pH = 1）中,从循环伏安图中可观察到PATP的不可逆电氧化峰。基于吸附PATP电化学氧化为4′-巯基-N-苯基醌二亚胺（NPQD）的反应机理,计算了电极表面PATP的覆盖度, 并在低激光功率下通过电化学表面增强拉曼光谱进行了氧化产物表征。通过电化学线性扫描伏安法及理论模拟计算,确定了PATP电化学氧化的动力学参数,即表观反应速率常数k及传递系数α,确定了生成阳离子自由基的步骤为速率控制步骤。

Electrochemical reactions on nanostructured noble electrodes have received much attention, however, the reaction mechanism and reaction kinetics are still difficult to be studied. Probe molecule can give an insight to the investigation of electrochemical reactions on noble electrodes with nanostructures. In this paper, the electrochemical process of p-aminothiophenol (PATP) adsorbed on the gold electrode was studied by electrochemical cyclic voltammetry and surface-enhanced Raman spectroscopy (SERS). Here, we used one-step sodium citrate reduction method (Frens method) to synthesize gold nanoparticles, which are used to construct the nanostructured gold electrode. The Raman electrolytic cell used was based on the traditional three-electrode electrolytic cell. The gold electrode was used as the working electrode (WE), the saturated calomel electrode (SCE) as the reference electrode (RE), and the platinum wire (Pt) as the counter electrode (CE). After the careful pretreatment of the gold electrode surface, the cell was assembled and placed on the platform of the XploRa instrument to get started. With the assistance of potentiostat, the SERS spectra at different potentials were acquired and combined together, a so-call electrochemical surface-enhanced Raman spectroscopic (EC-SERS) experiment. In a 0.05 mol·L^-1 sulfuric acid solution (pH = 1), an irreversible oxidation peak was found in the cyclic voltammogram, which is considered to correspond to the oxidation of the PATP molecule. The oxidation mechanism is proposed by combination of previous work in literature, and it is pointed out that the PATP molecule was initially transformed into cationic radical. Then, this cationic radical coupled with the PATP molecule to an intermediate NPQDH₂ , and finally electrochemically oxidized to 4'-mercapto-N-phenylquinone diamine (NPQD). On the basis of this mechanism, the surface coverage of PATP on the electrode surface was calculated and the coverage value was found to be larger at the nanostructured electrode due to the modification of gold nanoparticles than that of general gold electrodes. In the following, the electrochemical oxidation product was characterized by the EC-SERS spectra. Finally, we experimentally and theoretically studied the electrochemical oxidation kinetics of PATP on the gold nanoparticle-modified gold electrode (Au NPs@Au). The apparent reaction rate constant k and transfer coefficient α of PATP were calculated by electrochemical linear sweeping voltammetry and theoretical simulation, respectively, finding that the cationic radical formation step is the rate-limiting step. We believe that this work will no doubt stimulate the basic research of PATP on gold electrodes consisting of nanostructures and provide a guide to electrochemical kinetic research in other metal-adsorbate systems.