Ammonia (NH₃) plays an essential role in agriculture and modern industries. Electrochemical fixation of nitrogen (N₂) to ammonia (NRR) under ambient conditions with renewable electricity is a promising strategy to replace the industrial Haber-Bosch method. However, it usually suffers from extremely poor ammonia yield and low Faraday efficiency due to the poor electrocatalysts. Therefore, intensive studies have been devoted to developing efficient NRR catalysts till now. Among them, palladium (Pd) can capture protons in the aqueous phase to form stable α-PdH, which balances the competitive adsorption between nitrogen and protons as well as reduces the NRR reaction energy barrier. In addition, carbon-based materials have the characteristics of weak hydrogen adsorption capacity, wide potential window and abundant valence electrons. In this work, graphene composite powder supported palladium particles (PdNPs@GCP) were prepared by chemical reduction under ambient condition via adopting commercial hy-drophobic GCP as carbon carrier for nitrogen reduction reaction. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations results showed that the well-crystallized palladium particles were successfully loaded on the GCP surface, and GCP was conducive to exposure of more active sites. Raman and XPS spectra confirmed the existence of metal-carrier interaction. Benefitting from the specific structure-activity relationship of the PdNPs@GCP, the ammonia yield was 5.2 μg·h^-1·mg^-1 at -0.2 V vs. RHE and Faraday efficiency of 9.77% was achieved at -0.1 V vs. RHE in 0.1 mol·L^-1 Na₂SO₄ under natural conditions. Compared with pure palladium phase and GCP, the NRR activity of PdNPs@GCP was enhanced remarkably. The two-dimensional structure of GCP improved the mass transport efficiency and the hydrophobic surface could inhibit hydrogen evolution reaction through weakening the proton aggregation near the catalyst. Meanwhile, Pd particles on GCP would be favorable for nitrogen adsorption and activation, and the metal-carrier interaction of the catalyst could fine-tune the electronic structure of Pd, optimizing the adsorption and desorption of reaction intermediates to accelerate NRR. Strictly controlled experiments were carried out to eliminate any possible existing internal and external contaminations to confirm the source of the product NH₃. The morphology and component of the catalyst were almost unchanged after suffering a long-term (10 hours) electrochemical test, indicating good stability of PdNPs@GCP. In addition, no byproduct hydrazine (N₂H₄) was detected, proving the excellent NRR selectivity of the catalyst. This work provides a facile strategy for the fabrication of carbon-based composite catalysts, which has a promising prospect in electrochemical ammonia synthesis and other energy transformation field.

The sulfur mustard (bis(2-chloroethyl) sulphide, HD), one of highly toxic chemical weapon agents, can damage the alive tissue cells (such as skin, lung, respiratory mucosa and so on), and cause carcinogenic and mutagenic effects for a long time exposure, which imposes a great threat not only to the human health, but also to the sustainable development of the society. With its convenience, high sensitivity and rapid response, electrochemical technology exhibits considerable potential in the field-deployed detection toward HD, but the related reports are rare. Herein, the electrochemical behavior of HD on the bare Pt electrode was investigated by electrochemical measurements, and cyclic voltammetric (CV) results exhibited two well-defined oxidation peaks. According to the CV curves at different scan rates, the calculated the amount of transfer electron (n) and transfer coefficient value (α) reveal that the oxidation of HD followed absorption-controlled kinetics. To investigate the electrochemical behavior of HD on the bare Pt electrode, FT-IR and comparative experiments were carried out. The HD oxidation processes corresponding to the two oxidation peaks in CV plots were explained. The results show that the oxidation peaks at 1.02 V and 1.27 V attributed to the oxidation formations of bis(2-chloroethyl) sulfoxide and bis(2-chloroethyl) sulfone, respectively. The difference of HD oxidation peaks potential provides a new strategy to identify bis(2-chloroethyl) sulfoxide and bis(2-chloroethyl) sulfone. Square wave voltammetry (SWV) was used to quantitatively analyze HD with bare Pt electrode as the working electrode, a linear dependence of anodic oxidation peak current versus HD concentration was obtained in the range of 2.5 × 10^-5 ~ 6.0 × 10^-4 mol·L^-1, with a detection limit of 2.15 × 10^-5 mol·L^-1. Bare Pt, as the working electrode, which may not be modified furtherly, may distinguish the two oxidation peaks well. Additionally, the bare Pt working electrode demonstrated excellent anti-interfering ability in the presences of various inorganic ions and C₆H₁₂O₆, as well as excellent stability. The investigation in the electrochemical behavior of HD will provide a foundation for the electrochemical sensor and degradation toward HD. The next work should focus on the improvements of linear range and limit detection with loaded Pt nanoparticle and multidimensional supports.

Acetylpyrazine is naturally presented in hazelnuts, peanuts, and sesame seeds. As an important food additive, it is widely used in baked foods, meat, sesame and tobacco. At the same time, acetylpyrazine is also an important pharmaceutical intermediate, which is used in the syntheses of anti-tuberculosis drugs, anti-tumor, anti-malaria, anti-viral, antibacterial and treatments of epilepsy, pain and Parkinson’s drugs. At present, the synthesis methods of acetylpyrazine include oxidation method, multi-step method and Grignard reagent method, which have the disadvantages of low yield, cumbersome process, severe reaction conditions and high cost. In this study, acetylation of pyrazine was used to synthesize acetylpyrazine by electrochemical method for the first time. In this reaction, ammonium persulfate was electrolyzed on lead electrode to generate sulfate radicals, which react with pyruvic acid to generate acetyl groups, and followed by reacting with protonated pyrazines to synthesize acetylpyrazines under acidic conditions. Firstly, the effects of various electrolysis conditions on the yield of acetylpyrazine were investigated, and the optimal electrolysis conditions were obtained. A volume ration of 1:1 between ammonium persulfate saturated aqueous solution and methylene chloride solution containing 1 mol·L^-1 of pyrazine and 0.33 mol·L^-1 of pyruvic acid were used as the catholyte. A lead plate was used as the cathode. The electrolysis was carried out at the current density of 100 A·m^-2 under normal temperature and pressure. When the charge was 2.5 F·mol^-1, the yield of acetylpyrazine reached 44.12%. In addition, iron electrodes and added ferrous sulfate were used to investigate the influence of electrochemical-transition metal composite activation method on the yield of acetylpyrazine. However, the composite activation method has little effect on the improvement of the yield of acetylpyrazine. In general, the electrochemical synthesis of acetylpyrazine is simple and easy to control. Moreover, the reaction is gentler, the product purity is high, thus, the separation steps are simplified, and the production cost is reduced. The use of “clean energy” electrons instead of transition metal salts as the reducing agent is an environmentally friendly preparation method with broad prospects. At the same time, ammonium sulfate can be oxidized at the anode to generate ammonium persulfate, while acetylpyrazine is synthesized at the cathode. Therefore, pyrazine acetylation is a direct and effective method for preparing acetylpyrazine and electrochemical synthesis of acetylpyrazine has broad industrial application prospects.

The silicon-based anode materials have the potential to meet the ever-increasing demand for energy density in lithium-ion batteries market owing to their high theoretical specific capacity. Unfortunately, their commercialization was hindered by the continuous volume expansion. Herein, the expansion characteristics and corresponding mechanism of the silicon oxide and graphite-silicon oxide composites were investigated by in-situ displacement detection systematically. The results showed that the expansion property was improved by material process modifications. During the de/lithiation processes of graphite, the expansion ratio in 30% ~ 50% SOC changed little because of the small interlayer spacing variation of the intercalated graphite. Unlike the graphite anode, there was no obvious platform in the expansion ratio curve of silicon oxide except for the first lithiation process. As for the graphite-silicon oxide composite, the expansion ratio was influenced by two-component materials. In order to figure out how the expansion ratio of the composite changed, the capacity contributions of graphite and silicon oxide at various states of charge were calculated. It was found that the graphite dominated the initial stage of the first and second delithiation processes, while delithiation of silicon oxide started from 36% SOC, leading to the steep decline of the expansion ratio curves. During the second lithiation process, the capacity of the first 20% SOC mainly came from silicon oxide, after which the capacity proportion of graphite increased gradually. In 40% ~ 50% SOC region, the capacity contribution of silicon oxide was negligible, resulting in the reduction of expansion increase rate. The calculated capacity contribution of the component materials corresponded to the evaluation of expansion ratio, indicating the reliability of the calculation method, which could be applied in other graphite-silicon oxide composites with different proportions. The irreversible expansion of graphite mainly occurred at the first three charges processes, while the irreversible expansion of silicon oxide increased significantly over all cycling processes. The reversible expansion of silicon oxide decreased gradually as the capacity fading. And the total expansion of silicon oxide tended to be decreased from the third cycle because the decrement of reversible expansion surpassed the increment of irreversible expansion. Finally, the expansion ratio especially the irreversible expansion of silicon oxide was effectively reduced by optimizing the surface coating, prelithiation and particle size. These results could provide favorable guidance for developing high-performance silicon-based anode materials with stable structure and low expansion ratio.

Titanium (Ti) and its alloys are commonly used as engineering materials. Although they have been widely used in marine environments, they are also facing serious threats of biofouling. Therefore, it is necessary to investigate the relationship between electrochemical behavior and bioaffinity of titanium oxide film in seawater to explore effective surface treatment technology to reduce biofouling. In this work, the cathodic potential of -0.8 V_SCE and the passivation potential of 0.5 V_SCE were directly applied to the TA2 Ti in artificial seawater for potentionstatic polarization treatment to prepare two kinds of surface films with different states and then to monitor the electrochemical behaviors of the samples in different solutions, including culture medium with Nitzschia closterium f.minutissima or Navicula, natural seawater and sterilized natural seawater. Nitzschia closterium f.minutissima and barnacle cyprid were selected to explore the adhesion performance of the pure Ti polarized at different potentials. The results showed that the surface film of Ti sample polarized at 0.5 V_SCE was very stable in all the solutions, but the surface film of Ti sample polarized at -0.8 V_SCE was not stable in the early stage, and it would continue to grow under open circuit potential and gradually become stable after a long time immersion. Corrosion did not occur in all samples after 143 days of immersion. Biological adhesion test showed that lots of microalgae bodies and their metabolites covered life activity, and adhered to the two kinds of Ti sample surface after 143 days of immersion. These biological fouling attachments on the surface of Ti sample could be easily removed by washing with deionized water, implying that the adhesion strength of these attachments was relatively weak. No obvious damage was observed on the surface of Ti samples. This indicated that the two different titanium surface states have limited influence on the fouling of microalgae after a long time. However, the Ti sample polarized at 0.5 V_SCE had a lower Nitzschia closterium f.minutissima adhesion density and barnacle cyprids adhesion rate in the first three days, due to the differences in the composition and hydrophilicity of the two surface films. These results indicating that the antifouling property of Ti may be affected by different polarization treatments at the initial stage, while this effect was limited in a long-term immersion.

The relationship between the electrochemical activity of fuel cell catalysts and Pt particle size, as well as the catalyst support and co-catalyst is still unclear. In this work, FESEM, XRD, BET, TEM and CV techniques were adopted to investigate the effects of TiO₂ anatase (A)/rutile (R) phases content on the electrochemical activity of Pt electrocatalyst. The results showed that the anatase-rutile phase transformation occurred during the heat treatment of TiO₂ at 700 ~ 900 ^oC accompanied by the growth of two-phase crystalline size, and anatase was completely transformed into rutile at 900 ^oC. TEM results revealed that the ultrafine Pt electrocatalysts with the particle size of 1.8 ~ 2.8 nm were successfully prepared over the TiO₂-CN_x supports. The content of TiO₂ (A)/(R) phases had a “volcano-type” effect on both the BET surface area of TiO₂-CN_x supports and the real “effective” electrochemical active surface area (ECSA) of Pt/TiO₂-CN_x catalysts. When the rutile content was 25%, the TiO₂(25%R)-CN_x support and Pt/TiO₂(25%R)-CN_x catalyst had the largest specific surface area and the most electrochemical active sites, respectively. It is speculated that raising the rutile content, there might be a strong metal-support interaction between Pt nanoparticles and TiO₂(25%R)-CN_x support with the rutile content of 25%, which could anchor the ultrafine Pt nanoparticles, resulting in the highest ECSA of Pt/TiO₂(25%R)-CN_x catalyst. Therefore, the Pt/TiO₂(25%R)-CN_x became more suitable as a catalyst for fuel cells.

Metallic silver coating has been widely used in the fields of microelectronics industry, catalyst, sensor and preparation of magnetoresistive materials because of its excellent corrosion resistance, good lubricity, high conductivity, excellent decoration and high catalysis. Compared with the traditional aqueous solution system, the research on metal electrodeposition in ionic liquid system is developing rapidly. In addition, additives are the key factors in the silver plating process. Adding a small amount of organic or inorganic additives to the plating solution will significantly change the coating properties, such as improving brightness, hardness and ductility. In this paper, using choline chloride urea (ChCl-Urea) low eutectic solvents (DESs) as the base solution, cyclic voltammetry (CV), chronoamperometry (CA), Tafel polarization and other electrochemical methods were used. The effect of chloride ion on the electrochemical behavior of silver electrodeposition was deeply studied. The phase composition and micro morphology of the silver coating were also studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The existing forms and main discharge complexes in the presence of NH₄Cl in the plating solution were studied by the classical gerisher exchange current density method. The results showed that the addition of chloride ion in ChCl-Urea system changed the reduction potential of Ag⁺ (vs. Ag|AgCl), and Ag⁺ in the plating solution formed complex [AgCl_n]^1-n, which makes the reduction potential shift negatively from -0.85 V to -0.98 V. The increase of overpotential was conducive to the formation of silver coating with good performance. By comparing the fitting CA curve with the theoretical curve, it is found that the nucleation mode of Ag(I) in ChCl-Urea DES was related to the concentration of chloride ion. The nucleation mode at low concentration had the mixed nucleation characteristics of three-dimensional instantaneous nucleation and three-dimensional continuous nucleation, and the nucleation mode at high concentration conformed to three-dimensional instantaneous nucleation. The results of gerisher exchange current density analysis revealed that the main discharge complex ion in the plating solution was [AgCl₂]^-. The addition of chloride ion inhibited the formation of dendritic silver coating. At the same time, this paper provides a method for preparing compact spherical pure silver coating. As means of preparing nanospherical silver, electroplating is the main direction of future research. Basic research on relevant additives is also essential. In the process of silver plating, the action mechanism of additives needs to be further studied. This plays an important guiding role in the development of electroplating additives and electroplating process.

It is preferred to simultaneously recover resource and energy from waster. Sulfur dioxide, SO₂, a common air pollutant, a potential energy resource, is a key link to sulfur nature circulation. SO₂ can be conversed to NH₄HSO₃ and (NH₄)₂SO₃ during the ammonia desulfurization process, which can be used to produce (NH₄)₂SO₄ fertilizer. For high quality (NH₄)₂SO₄ fertilizer and high heat transfer efficiency of the evaporative crystallization, HSO₃^- or SO₃^2- needs to be oxidized to form SO₄^2- before evaporative crystallization. Anodic oxidation of HSO₃^- or SO₃^2- coupled with hydrogen evolution can significantly reduce cost of hydrogen evolution due to a low reaction potential. This work uses a filter-press membrane electrode assembly electrochemical reactor to recover commercially valuable (NH₄)₂SO₄ fertilizer and produce hydrogen. It can simultaneously achieve waster recycle and energy storage, which is conformed to the domestic circulation and dual carbon goals. The electrooxidation mechanisms and dynamic parameters of (NH₄)₂SO₃ and NH₄HSO₃ on homemade PtPd_2.75/C catalyst were investigated, particularly by cyclic voltammetry and rotating disk electrode system. According to Randles-Sevĉik equation and Levich equation, the number of the electron transfer during the electro-oxidation of SO₃^2- or HSO₃^- is 1.86. The diffusion coefficients of SO₃^2- and HSO₃^- are 2.29 × 10^-6 cm²·s^-1 and 1.18 × 10^-5 cm²·s^-1, respectively. A 1 cm × 1 cm electrolyser was homemade by graphite. The desulfurization wastewater was used as the anolyte, while water as the catholyte. The anolyte and catholyte were separated by a proton exchange membrane. The homemade PtPd_2.75/C catalyst was used as both sulfite oxidation catalyst and hydrogen evolution catalyst. The catalyst was loaded to carbon clothes firstly, and then hot-pressed to the proton exchange membrane to fabricate the membrane electrode assembly. The influences of operation conditions on the electrolyser performances have been studied by potentiodynamic scans and electrochemical impedance spectroscopy. The optimal conditions were chosen as follow: pH = 7.5 of the ammonium sulfite wastewater as the anolyte, pure water as the catholyte, 50 ^oC. The electrolyser exhibited excellent SO₃^2- electro-oxidation performance and stability. Under the optimal experimental conditions, the electrolyser could achieve 294.63 mA·cm^-2 at 1.5 V. At a current density of 200 mA·cm^-2, the SO₃^2- conversion rate could reach 94% without exceeding the applied cell voltage of 2 V. It could produce 0.70 t ammonium sulfate and 2.98 kg hydrogen when 1 m³ ammonium sulfite wastewater was electrolyzed for 20 h. The electricity consumption was 137.24 kWh per m³ wastewater, which can create a profit of 1302.70 yuans. Such a strategy has shed a light on further development towards industrial application.