The electrochemical quartz crystal microbalance (EQCM) and density functional theory (DFT) have been combined to study the special reaction between thiourea (TU) and metal cluster and the mechanism of the replacement of Cu by Sn in the presence of TU for the first time. The natural bond orbital (NBO) charge of the top copper atom obviously shifts toward positive values compared to the interaction behavior of single and double (SdC) regions with Cu4 cluster via the DFT method. This can explain the reason for the accelerating corrosion process at higher TU concentrations since the copper atoms can change to cuprous ions in this process. It is proven that the thermodynamically impossible replacement of Cu by Sn can occur in the presence of TU by reducing the OCP of the copper electrode to a more negative value than the redox potential of Sn2+/Sn. The DFT investigation on the interactions between delocalization (SdC) and (NsC) regions in TU and Cu4 or Sn4 cluster indicates that the highest molecular occupied orbital (HOMO) of the SdC region has better than adequate to the lowest unoccupied molecular orbital (LUMO) of Cu4 cluster than that of Sn4 cluster. The replacement mechanism deduced based on the first-principles analysis is universally applicable to the alloy deposition, corrosion inhibition, and surface treatment.

In this work, the oxidation mechanism of hypophosphite anion (H2PO2-) in acidic and alkaline media in the presence of Ni(Ⅱ) specie was investigated by using electrochemical impedance spectroscopy (EIS) and density functional theory (DFT). In EIS, three major electrochemical processes in the electroless deposition process were found, when the solution pH ranged from 5.5 to 9.5. To understand the microscopic mechanisms involved, all participate species in the reaction pathways were calculated by the DFT method along with a natural bond orbital (NBO) analysis. Two emulating reactions were demonstrated: Path (Ⅰ) passes through a primary dehydrogenation (D-RP), and Path (Ⅱ) includes a primary addition of OH-(A-RP) on the hypophosphite anion. By comparison of the energy levels of all species, it can be concluded that Path (Ⅱ) is energetically favorable under both acidic and alkaline conditions. The DFT and NBO analysis can provide strong evidence for the loops detected in the EIS, especially especially for the inductive loop (IL-M) in the medium-frequency domain that is caused by the formation of [NiI-H3PO2(OH)] and the capacitive loop (CL-L) in the lowfrequency domain by [H2PO2(OH)]. The combination of electrochemical analysis (EIS) and first principle theory (DFT) analysis proves that it is helpful to explore the nature of the interaction between anodic and cathodic reactions in the electroless deposition process.

为了探索有机物在固定后光催化剂上的降解行为，将TiO2（锐钛型）粉末固定在多孔泡沫镍上，以一只6W主波长为365nm的紫外线杀菌灯为光源，研究了磺基水杨酸（SSal）在TiO22Ni体系上的光催化降解。结果表明，SSal的降解动力学可采用Langmuir-Hinshelwood（L2H）方程来描述。通过测定降解反应的半衰期和测定初始速率的方法确定了L2H方程的参数，两种方法的结果相吻合。还研究了SSal的光催化降解反应速率与pH值和温度的关系。结果表明，当pH值为7.5左右时，SSal的光催化降解最为有利;当温度从20℃升至50℃时，SSal的光催化降解加快。通过考察不同pH值时SSal在TiO2/Ni体系上的吸附能力探讨了反应初始速率与pH值的关系。

建立了以刮浆工艺制得的TiO2/Ni为工作电极、泡沫镍为对电极、饱和汞电极为参比电极的光电催化反应体系，研究了在磺基水杨酸（SSal）的光电催化降解过程中，外加电压和溶液pH值对降解速度的影响。实验发现，外加阳极偏压为700mV时，SSal能发生有效降解，降解速率受溶液pH值的影响；随着SSal降解的进行，阴极表面电阻出现较大的变化，另外还研究了SSal光电催化降解过程中的电流变化特征。

TiO2 treated in hydrogen atmosphere showed enhanced photocatalytic activity in degrading the sul-fosalicylic acid (SSal). The results of the electrochemical impedance spectroscopy (EIS) investigation showed that the diameters of the capacitive arcs for the H-TiO2 were much smaller than those of bare TiO2 and thermally treated TiO2 in air, indicating that the charge transfer of the H-TiO2 occurs more rapidly, thus inviting a higher photocatalytic activity. When an external bias was applied on the H-TiO2, the arc of the EIS Nyquist plot decreased obviously than without the bias, suggesting more efficient separation of the photo-generated carriers.