The photocatalytic degradation of aniline was studied in annular photoreactor, with 2 6W (EmaxD365 nm) UV lamp as light source, borosilicate glass as wave filter and titanium dioxide immobilized on porous nickel as catalysts. Parameters such as the initial concentration, flow rate, initial pH, dissolved oxygen, electrolyte, hydrogen peroxide addition, temperature and external potential bias affecting the degradation rate of aniline were studied. The results showed that photocatalysis is an effective process for the degradation of aniline. The activated energy for the photocatalytic degradation of aniline is 6.13 kJ mol-1. The initial quantum yield is 1.89% for aniline 1.10×10-4 mol l-1. Total mineralization requires a much longer illumination time than the disappearance of anilines. The external potential bias can largely improve the efficiency of photocatalytic degradation of aniline. The degradation kinetic of aniline can be described by Langmuir-Hinshelwood equation.

To well describe the electro-Fenton (E-Fenton) reaction in aqueous solution, a new kinetic model was established according to the generally accepted mechanism of E-Fenton reaction. The model has special consideration on the rates of hydrogen peroxide (H2O2) generation and consumption in the reaction solution. The model also embraces three key operating factors affecting the organic degradation in the E-Fenton reaction, including current density, dissolved oxygen concentration and initial ferrous ion concentration. This analytical model was then validated by the experiments of phenol degradation in aqueous solution. The experiments demonstrated that the H2O2 gradually built up with time and eventually approached its maximum value in the reaction solution. The experiments also showed that phenol was degraded at a slow rate at the early stage of the reaction, a faster rate during the middle stage, and a slow rate again at the final stage. It was confirmed in all experiments that the curves of phenol degradation (concentration vs. time) appeared to be an inverted ‘‘S’’ shape. The experimental data were fitted using both the normal first-order model and our new model, respectively. The goodness of fittings demonstrated that the new model could better fit the experimental data than the first-order model appreciably, which indicates that this analytical model can better describe the kinetics of the E-Fenton reaction mathematically and also chemically.

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.

Thiswork investigated the effect of co-existing organic matters on aqueous Cr(VI) reduction by electrodeposited zero-valent iron (ED Fe0) at neutral pH. The ED Fe0 prepared in a solution containing mixture of saccharin, l-ascorbic acid and sodium dodecyl sulfate showed higher activity in reducing the aqueous Cr(VI) at neutral pH than that prepared without any organic presence. XRD and SEM indicated that the structure of ED Fe0 was significantly improved to nano-scale by the presence of organic mixture in the preparation solution. Further, the ED Fe0 activity in the Cr(VI) reduction at neutral pH was increased by the co-existence of citric acid or oxalic acid in the chromate solution. Electrochemical impedance spectroscopy (EIS) demonstrated that the corrosive current increased with the concentration of organic matter in the reaction solution. With the co-existing organic matters in the preparation solution, the ED Fe0 corroded more rapidly due to its nano-size, thus the Cr(VI) reduction by the ferrous iron was accelerated. With the co-existing organic matters in the reaction solution, the Cr(VI) reduction was accelerated by a Fe(II) complex as the main electron donor, and a prevention of the passivation due to the Fe(III) and Cr(III) complexes also accelerated the Cr(VI) reduction.