Antimony is a chemically stable metal that has been widely used in industry, military and other fields. The use of electrodeposition to prepare antimony coating has the advantages of simple operation and low cost. The deep eutectic solvent (DES) is a eutectic mixture composed of a hydrogen bond donor and a hydrogen bond acceptor at a fixed molar ratio. It has the advantages of wide electrochemical window, high thermal stability, easy preparation, and low cost. Selecting DES as the electrolyte for electrodeposition can avoid the hydrogen evolution reaction of the aqueous system and the toxicity of ionic liquids. In recent years, there have been more and more researches on the preparation of metal coatings by electrodeposition in DES. In this work, choline chloride (ChCl) and ethylene glycol (EG) were heated and mixed at a molar ratio of 2:1 to form DES, while antimony(III) chloride (SbCl₃) was added to form an electrolyte. At room temperature, Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy were used to analyze the structure of the electrolyte. The results show that there were a large number of hydrogen bonds in DES, and that the existence of hydrogen bonds played an important role in the formation of DES. Sb(III) existed in the eutectic solvent in the form of [SbCl₄]^-. Using a three-electrode system, cyclic voltammetry was used to study the electrochemical behaviors in DES at different sweep speeds (25 ~ 55 mV·s^-1), different temperatures (333 ~ 363 K), and different concentrations (0.01 ~ 0.10 mol·L^-1) of Sb(III). The results indicate that at 343 K, the reduction of Sb(III) in ChCl-EG became a quasi-reversible reaction controlled by diffusion through one-step three-electron transfer. The diffusion coefficient at 343 K was 3.06×10^-9 cm²·s^-1. As the temperature and concentration of the electrolyte increased, the overpotential required for the reduction of Sb(III) decreased. The nucleation mode of electrochemical reduction of Sb(III) in ChCl-EG was studied by chronoamperometry. According to the Scharifker-Hills nucleation model, at 343 K, the nucleation of Sb on the tungsten electrode follows three-dimensional instantaneous nucleation. In addition, the electrodeposition products were characterized by SEM and XRD. SEM observations reveal that the applied deposition potential is the main driving force for the reduction of Sb(III). As the deposition potential increased from -0.33 V to -0.41 V, the morphology of the electrodeposition product gradually changed from granular crystals to dendrites. XRD data shows that there was Sb phase in the deposited product obtained at -0.41 V. In addition, the Cu₂Sb phase was presented due to the interfacial reaction between the newly deposited Sb and the substrate Cu to form intermetallic compounds. Future research can continually study the influences of such inorganic additives as boric acid (BA), ammonium chloride (NH₄Cl), and organic additives includingethylene-diaminetetraacetic acid (EDTA), N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) and Idranal VII (HEDTANa₃) on Sb electrodeposition.

This paper studies the influence of electrode shape on the lithiation process of lithium ion batteries. Both experimental observation and numerical simulation are employed to investigate the competitive interaction between the diffusion of lithium ions in both solid and liquid phases and the lithium intercalation reaction at the electrode surface. Experimental cells were prepared with the anode and cathode being placed parallel, leaving the latter embracing the former. An experimental device based on CCD camera was set up for in situ observation of electrode lithiation. The lithiation levels of the graphite anodes were estimated according to the observed color profile. Three shapes of electrodes, namely, circular, square and triangular shapes, were investigated. It is found that the lithiation levels were not uniform for all cases. The edge areas of all anodes were lithiated to approach saturation quickly, meanwhile the core areas of the anodes remained in very low lithiation level. The sharp tips of the electrode with high curvature were more likely to have more lithium ions intercalated, leading to quick saturation and even lithium dendrite deposition. Compared with the electrode voltage-capacity curves, although the recorded reacted capacity was equal to the theoretical capacity of the anode at the end of charge operation, the color profiles show that the anodes were far from full saturation. In addition, large clusters of lithium dendrite depositions were found at the electrode edges. It indicates that quite a portion of lithium ions were consumed in side reactions instead of being intercalated into the anode. Numerical simulations reveal that the non-uniform lithiation is induced due to the combination effects of the electric field distribution, the lithium flow in the electrolyte and the lithium concentration distribution in the active material. The electrode edges lead to a singular distribution of the electric field in the electrolyte, resulting in a concentrated flow of lithium ions in an electrolyte. Therefore, the electrode edges are subjected to excessive supply of lithium ions in an electrolyte, leading to quick saturation and even dendrite deposition in the edge areas. At the same time, the core area of electrode cannot capture enough lithium ions from an electrolyte and, therefore, remain in low lithiation level. This effect is more significant in the electrodes with sharper tips. For example, the square and triangular anodes show more heterogeneous distribution of lithiation level than the circular anodes. In addition, more lithium dendrites are found around the electrode tips. Therefore, electrode designs with irregular shapes should be avoided to minimize the edge effects. The electrode surface should also be prepared smoothly to reduce the edge effects due to rough surfaces. This work sheds some lights on the understanding the lithiation process of lithium-ion batteries. It would be helpful in the design of lithium-ion batteries.

Lithium metal is considered as an ideal anode material for next-generation high energy density batteries with its high specific capacity and low electrode potential. However, the high activity of lithium metal can lead to a series of safety issues. For example, lithium metal will continuously react chemically with the electrolyte, forming unstable the solid electrolyte (SEI) films. In addition, lithium dendrites can be formed during cycling, which can puncture the SEI film and cause short circuits in the battery. These drawbacks greatly hinder the commercial application of lithium metal. To solve the above problems, it is important to understand the structure of SEI and the underlying mechanism of its formation as a guide for rational design. Quantum mechanics (QM) has been demonstrated as an effective tool to investigate the chemical reactions and microscopic atomic structures of SEI. However, QM is computationally too expensive to be used for large-scale and long-term theoretical simulations. Instead, the molecular mechanics (MM) method has much orders higher computational efficiency than QM, and can be used for large-scale and long-time theoretical simulations. However, the accuracy of MM is usually not guaranteed, especially for complex SEI. Therefore, a practical solution is to combine the advantages of both. In this work, we use the hybrid ab initio and reactive molecule dynamics (HAIRs) approach to describe chemical reactions with the accuracy of quantum chemistry and improve the computational efficiency by more than 10 times with mixing QM and MM. Using this method, we have investigated the interfacial reaction mechanism of two electrolyte solutions, 1 mol·L^-1 LiTFSI-DME (dimethoxyethane) and 1 mol·L^-1 LiTFSI-EC (ethylene carbonate) with the lithium metal anode. The simulation results show that TFSI anion prefers to be decomposed, while DME does not, thus, TFSI plays the vital role of protecting DME. However, in the LiTFSI-EC system, both TFSI anion and EC are decomposed, indicating that EC is less stable and not suitable to the formation of stable SEI. Thanks to the computational efficiency of the HAIRs method, we have completed the 1 ns simulation in a few days. Using the hardware, the above calculation would take at least one to two months if only the QM method was employed. Meanwhile the long HAIRs calculation shows that for the simulation of chemical reactions in SEI, at least 1 ns is essential. Instead, previous molecular dynamics (MD) simulations with a few ps, or tens of ps, are insufficient to fully capture the critical chemical reactions. The above simulation results provide reliable experience for the computational simulation study of SEI formation, and lay the theoretical foundation for the rational design of electrolytes and the development of high-performance electrolyte solution systems.

Proton exchange membrane fuel cell (PEMFC) is a new type of energy device, a relatively excellent way to achieve carbon neutrality. However, due to the relatively slow reaction rate of oxygen reduction reaction (ORR) at the cathode, platinum (Pt) is the key material of the cathode catalyst. However, Pt is a kind of noble metal, and its high cost restricts the PEMFC commercialization process. At present, the main approach is to combine transition metals with Pt to prepare Pt-based alloys and to reduce the use of Pt. Pt-based alloys are excellent catalysts for ORR, improving both the activity and stability, and increasing the Pt utilization rate and the number of active sites of the catalyst. In this paper, by employing nitrogen-doped carbon material derived from a metal organic framework as a support, Pt/NC, Pt₃Zn/NC-L and Pt₃Zn/NC-H catalysts were successfully synthesized by impregnation, freeze-drying and simple heat treatment. The particle sizes were around 2 nm and uniformly supported on the carbon. Raman data shows that the defect degree was slightly reduced after loading metal, mainly because the nanoparticles would be anchored in the defect position, and the metal would help the graphitization of carbon at high temperature. The introduction of Zn into Pt caused the Pt lattice to be shrunk, which shortens the Pt-Pt bond length, and optimizes the combination of Pt and oxygen-containing intermediates, ultimately enhances the ORR activity. On the highly alloyed Pt₃Zn/NC-H catalyst, the half-wave potential was 0.903 V, which is a positive shift of 57 mV compared with commercial Pt/C, moreover, the mass activity and area specific activity at 0.9 V were 4.50 times and 3.33 times to those of commercial Pt/C, respectively. The 10000-cycle stability test was carried out in an O₂-saturated 0.1 mol·L^-1 HClO₄ solution at 0.6 ~ 1.0 V (vs. RHE). The mass activity and area specific activity of commercial Pt/C decreased by 25.00% and 23.80%, respectively, while Pt₃Zn/NC-H catalyst revealed excellent stability. Transmission electron microscopic (TEM) observation shows that after the stability test, the nanoparticles were well dispersed on the nitrogen-doped carbon support, however, the commercial Pt/C became a slight agglomeration. Small particle sized Pt-based catalysts, constructed with a metal-organic framework-derived nitrogen-doped carbon material as a carrier, can improve the electrocatalytic activity and stability toward ORR, providing new ideas for the design and construction of Pt-based oxygen reduction catalysts.

Acetylpyrazine is an important spice and also plays important roles in biology, medicine and other fields. However, the wastewater containing ammonium persulfate, ferric ion (Fe³⁺), pyrazine, and a large amount of ammonium sulfate was produced during the production of acetylpyrazine. In this study, ammonium sulfate in acetylpyrazine wastewater was electrolytically converted into ammonium persulfate for economic benefits. Using platinum as an anode and graphite as a cathode, the influence factors of the electrolysis process (including the composition of the anolyte, the current density, the temperature, etc.) were firstly investigated without interference from other compositions. Under the optimal condition, namely, the anolyte (50 g) composition consisted of 37wt.% ammonium sulfate, 15wt.% sulfuric acid, and 0.06wt.% ammonium thiocyanate, and the catholyte composition was 25wt.% sulfuric acid, the current density was 8000 A·m^-2, the anolyte temperature was 30 ^oC, and the passed electric charge was 2 A·h, the current efficiency for the production of ammonium persulfate could be as high as 89.65% when the mass fraction of ammonium persulfate reached to 15.83wt.%. Then, the effects of Fe³⁺ and pyrazine on electrolysis were investigated. The presence of Fe³⁺ in the anolyte would affect the purity of ammonium persulfate precipitation, while the presence of pyrazine would affect the current efficiency for the production of ammonium persulfate, for example, the current efficiency would reduce by 10% when the concentration of pyrazine in the anolyte was only 0.015 mol·L^-1. Therefore, it is necessary to remove Fe³⁺ and degrade pyrazine in the wastewater before electrolysis. And according to the composition of acetylpyrazine wastewater, the simulated wastewater was prepared to investigate the pretreatment effect. The concentration of Fe³⁺ was dramatically reduced to 2.7 mg·L^-1 when the pH value of the simulated wastewater was adjusted to about 7 through the addition of ammonia. Meanwhile, the sulfate radical oxidation method was adopted to degrade pyrazine in the simulated wastewater, showing 98.43% of the pyrazine degradation by activating the ammonium persulfate of 0.65 mol·L^-1 to generate the sulfate radicals at 80 ^oC. Finally, the current efficiency of 85.21% was achieved by using the pretreated acetylpyrazine actual wastewater as an anolyte, which proved the feasibility of electrochemical conversion of ammonium sulfate to ammonium persulfate in acetylpyrazine wastewater.

Ammonia is an important industrial raw material and a potential green energy. Using renewable energy to convert nitrogen into ammonia under ambient condition is an attractive method. However, the development of efficient photoelectrochemical ammonia synthesis catalysts remains a challenge. Perovskite such as BaSrTiO₃ (BST) is a good photocatalytic material. However, BST is active under ultraviolet light and has a high recombination rate of photogenerated electron-hole pairs. By dispersing precious metals, it can effectively regulate the absorption of sunlight by BST. In this work, we used a two-step method to prepare BST. The H₂PtCl₆·6H₂O solution was dispersed on the BST, and then followed by calcination in a tube furnace to obtain Pt@BaSrTiO₃ (Pt@BST). X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were utilized to analyze the structures, morphologies, and surface chemical composition of the synthesized materials. Results showed that the well-crystallized Pt particles were successfully loaded onto the BST surface, and Pt and BST interacted to produce a metal-semiconductor heterojunction, improving the performance of N₂ reduction. The N₂ adsorption and desorption isotherms showed that the increase in the specific surface area helped the catalyst to adsorb N₂, and the contact area with H₂O also increased, which promotes the occurrence of NRR and thus produces more NH₃. UV-Vis and PL spectroscopic techniques were used to characterize and analyze optical properties of the obtained catalyst. It is indicated that decoration of Pt reduces the band gap of the catalyst and increases the visible light absorption range, in addition, further enhances the charge separation and transfer, inhibits the recombination of electron-hole pairs, and improves the efficiency of charge separation. The performances of BST and Pt@BST for photoelectric catalytic synthesis of ammonia under ambient condition were studied. The yield of ammonia first increased and then decreased with the increase of Pt content. When the Pt content was 4wt%, the yield was the highest. The results showed that the ammonia yield of Pt@BST was 26.57 × 10^-8 mol·h^-1·mg^-1 and Faraday efficiency (FE) was 5.43% at -0.3 V (vs. RHE) in 0.1 mol·L^-1 Na₂SO₄ under natural conditions, suggesting that the ammonia yield of Pt@BST was twice that of pure BST (13.12 × 10^-8 mol·h^-1·mg^-1). We conducted control experiments of ¹⁵N₂ isotope and Ar in order to eliminate internal and external environmental pollution. Confirming that the detected NH₃ was produced exclusively via nitrogen reduction reaction. After recycling the test six times at -0.3 V (vs. RHE), both FE and ammonia yield rate showed a slight variation, indicating the high stability of Pt@BST during N₂ reduction process. This work provides a simple strategy for further designing the preparation of noble metal modified perovskite catalysts, and has promising application prospects in ammonia synthesis under ambient condition.

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.

The purpose of this study is to optimize the electrochemical degradation of oxytetracycline (OTC) in water using a low cost and simple preparation method. In this paper, the Fe₃O₄ magnetic nanoparticles were used as catalysts to activate the electrochemical oxidation system of peroxydisulfates (PDS) which acted as electrolytes to provide active free radicals in order to improve the degradation of OTC under the condition of applying current. As one of the tetracycline antibiotics (TCs), OTC is one of the most used antibiotics in the world, therefore, it is necessary to study the effective degradation of OTC. By means of field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and other characterization methods, it was proved that the Fe₃O₄ magnetic nanoparticles at about 150 nm were successfully prepared by a simple hydrothermal method. Firstly, it is suggested that the application of electric current and the presence of Fe₃O₄ magnetic nanoparticles are necessary for the effective degradation of OTC. Secondly, the optimal reaction experiment confirmed an excellent OTC degradation ability by combination of Fe₃O₄ magnetic nanoparticles and current. The optimal reaction conditions were as follows: the concentration of PDS was 4.0 mmol·L^-1, the initial pH value of the solution was 7, and the current density j was 30 mA·cm^-2. When the dosage of Fe₃O₄ magnetic nanoparticles was 0.1 g·L^-1 and the initial OTC concentration was 70 mg·L^-1, the degradation rate of OTC could reach 88.75% within 60 min and the rate constant of the first-order kinetics simulation curve could reach 0.06069. In addition, the variation of UV-vis characteristic peak of OTC during the degradation process revealed that the change of OTC concentration was not due to simple physical adsorption, but through the complete degradation of active free radicals. In addition, after the continuous circulation of Fe₃O₄ magnetic nanoparticles for 5 times, the degradation rate of OTC could still reach more than 68%, proving that Fe₃O₄ magnetic nanoparticles have good catalytic stability. The presence of Fe₃O₄ magnetic nanoparticles and the application of electric current could promote the formations of SO₄^·- and ^·OH, respectively. The radical quenching experiments showed that both SO₄ ^·- and ^·OH were active free radicals degraded by antibiotics. This work uses a low-cost catalyst to enhance an electrochemical degradation of OTC. The experimental operation is simple, the degradation rate is fast, and the energy consumption is low. It is promising to practical applications.