Shibin Liu

Separation of low concentration of cesium ion from wastewater by electrochemically switched ion exchange method: Experimental adsorption kinetics analysis

A series of experiments were performed to evaluate the continuous separation of cesium based on an electrochemically switched ion exchange (ESIX) process using a diaphragm-isolated reactor with two identical nickel hexacyanoferrate/porous three-dimensional carbon felt (NiHCF/PTCF) electrodes as working electrodes. The effects of applied potential, initial concentrations and pH values of the simulation solutions on the adsorption of cesium ion were investigated. The adsorption rate of cesium ion in the ESIX process was fitted by a pseudo-first-order reaction model. The experiments revealed that the introduction of applied potential on the electrodes greatly enhanced the adsorption/desorption rate of Cs(+) and increased the separation efficiency. H(3)O(+) was found to play a dual role of electrolyte and competitor, and the adsorption rate constant showed a curve diversification with an increase in pH value. Also, it was found that the electrochemically switched adsorption process of Cs(+) by NiHCF/PTCF electrodes proceeded in two main steps, i.e., an ESIX step with a fast adsorption rate and an ion diffusion step with a slow diffusion rate. Meanwhile, the NiHCF/PTCF film electrode showed adsorption selectivity for Cs(+) in preference to Na(+).

Continuous Separation of Cesium Based on NiHCF/PTCF Electrode by Electrochemically Switched Ion Exchange

Abstract Nickel hexacyanoferrate (NiHCF) film was synthesized on porous three-dimensional carbon felt (PTCF) substrate by repetitious batch chemical depositions, and the NiHCF/PTCF electrode was used as electrochemically switched ion exchange (ESIX) electrode in a packed bed for continuous separation for cesium ions. The morphologies of the prepared electrodes were characterized by scanning electron microscopy and the effects of solution concentration on the ion-exchange capacity of the electrodes were investigated by cyclic voltammetry technique. Cycling stability and long-term storage stability of NiHCF/PTCF electrodes were also studied. The NiHCF/PTCF electrodes with excellent ion-exchange ability were used to assemble a diaphragm-isolated ESIX reactor for cesium separation. Continuous separation of cesium and regeneration of NiHCF/PTCF electrode based on the diaphragm-isolated reactor were performed in a laboratory-scale two-electrode system.

Ordered mesoporous carbon-supported CoFe2O4 composite with enhanced lithium storage properties

AbstractnA high and stable reversible specific capacity (1277.7xa0mAhxa0g−1) was successfully achieved by the CoFe2O4/ordered mesoporous carbon nanohybrids (CFO/CMK-3) composite anode at the current density of 0.1xa0Axa0g−1 after 100 cycles. CFO/CMK-3 electrode also exhibited a stable capacity up to 733.2 and 482.6xa0mAhxa0g−1 at the current densities of 0.5 and 1xa0Axa0g−1 after 500 cycles, respectively. The CFO particles were found to be uniformly distributed inside the pore channels of CMK-3. Structure characterization before and after 100 tests revealed that the specific CMK-3 mesoporous structure and CFO crystallites remained unchanged. The stability of the anode composite stability and the rapid redox capability of CFO gave rise to superior lithium storage capacity and excellent cycling stability. CFO/CMK-3 showed a great promise to serve as anode for high-performance lithium-ion battery.

Investigation of carbon-supported Ni@Ag core-shell nanoparticles as electrocatalyst for electrooxidation of sodium borohydride

Carbon-supported Ni@Ag core-shell nanoparticles were synthesized and used as the anode electrocatalyst for direct borohydride-hydrogen peroxide fuel cell (DBHFC). The morphology, structure, and composition of the as-prepared electrocatalysts are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). Electrochemical characterizations are performed by cyclic voltammetry (CV), chronoamperometry (CA), linear scan voltammetry with rotating disk electrode (LSV RDE), and fuel cell test. The catalytic behaviors and main kinetic parameters (e.g., Tafel slope, number of electrons exchanged, exchange current density, and apparent activation energy) toward BH4‐ oxidation on Ag/C and Ni@Ag/C electrocatalysts are determined. Results show that the as-prepared nanoparticles have a core-shell structure with the average size approximately 13xa0nm. The kinetics of NaBH4 oxidation is faster for Ni@Ag/C than that for Ag/C. Among the as-prepared catalysts, the highest transition electron value and the lowest apparent activation energy are obtained on Ni1@Ag1/C; the values are 4.8 and 20.23xa0kJxa0mol−1, respectively. The DBHFC using Ni1@Ag1/C as anode electrocatalyst and Pt mesh (1xa0cm2) as cathode electrode obtains the maximum anodic power density as high as 8.54xa0mWxa0cm−2 at a discharge current density of 8.42xa0mAxa0cm−2 at 25xa0°C.

Catalytic conversion of methanol to aromatics over nano-sized HZSM-5 zeolite modified by ZnSiF6·6H2O

ZnSiF6-modified nano-sized HZSM-5 zeolites (NZ2, NZ3 and NZ4 catalysts) were prepared and investigated as catalysts for the conversion of methanol to aromatics. Moreover, the ZnNZ1 catalyst, prepared by ion exchange using zinc nitrate, was also introduced as a reference sample. The effects of modification on the framework, textural properties and acidity of the parent nano-sized HZSM-5 zeolite (NZ1) were investigated by XRD, FT-IR, 29Si MAS-NMR, SEM, N2 adsorption–desorption, ICP, NH3-TPD, infrared spectroscopy of adsorbed pyridine (Py-IR), UV-vis spectra, X-ray photoelectron spectroscopy (XPS) and n-butylamine and tert-butylamine titration. The results showed that the amount of total acid sites, especially the external surface acid sites of the NZ2, NZ3 and NZ4 catalysts, significantly decreased, which may largely be attributed to the passivation effect of SiF62− on the surface acidity of the parent NZ1 catalyst. Moreover, the amount of Lewis acid sites (L acid sites) increased, whereas the amount of Bronsted acid sites (B acid sites) obviously decreased with the introduction of zinc species. The emergence of new Zn-Lewis acid sites (⊖ZO⋯H⋯O–Zn⊕ species) was beneficial to improving the selectivity to BTX (benzene (B), toluene (T) and xylene (X)) due to their high activity for dehydroaromatization. The FT-IR spectra in the OH− vibration region and the 29Si MAS-NMR spectra show that the treatment of ZnSiF6 could effectively repair partial lattice defects of zeolite and could thus improve the catalyst stability. TG analysis of all the deactivated catalysts showed that the coke amount and the average rate of coke formation decreased over NZ2, NZ3 and NZ4 catalysts, and this may largely be ascribed to their lower surface acidity. The catalytic performance of these materials on the conversion of methanol to aromatics showed that the NZ3 catalyst had the highest selectivity to BTX of about 51.3% and the longest catalytic lifetime of about 234 h under the operating conditions of T = 425 °C, p = 0.1 MPa and WHSV = 0.8 h−1. The improvement in the selectivity to BTX and the catalyst lifetime of the NZ3 catalyst could be ascribed to the synergistic effect among the Zn-Lewis acid sites (⊖ZO⋯H⋯O–Zn⊕ species), external surface acidity and intact framework structure.

Performance of Pt/C Doped with Ni for Oxygen Electro-Reduction in Alkaline Media

Abstract Carbon-supported Pt-Ni catalyst samples were prepared by the colloidal method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopic (XPS) and transmission electron microscopy (TEM). Potentiodynamic was used to measure the performance of the electro-catalysts for the oxygen electro-reduction. The results indicate that the Pt-Ni alloy particles are distributed homogeneously on the carbon surface, and their particle sizes are 3−5 nm. In the same alkali concentration solution, the activity and methanol-tolerance of Pt nano-particle catalysts are greatly enhanced by doping Ni. For the catalyst, the optimum atom ratio of Pt to Ni is Pt 50 Ni 50 /C, and its methanol-tolerance is enhanced markedly as compared with Pt/C. The maximal current of the oxygen electro-reduction over Pt 50 Ni 50 /C reaches 106 mA/mg, and the onset over potential is 50 mV less than that over Pt/C in 0.1 mol/L KOH solution.

Electrochemical Characterization of Ion Selectivity in Electrodeposited Nickel Hexacyanoferrate Thin Films

The ion selectivity of electrodeposited nickel hexacyanoferrate (NiHCF) thin films was investigated using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). NiHCF thin films were prepared by cathodic deposition on Pt and Al substrates. EJS and CV curves were determined in 1 mol/L (KNO3+CsNO3) and 1 mol/L (NaNO3+CsNO3) mixture solutions, which were sensitive to the concentration of Cs(superscript +) in the electrolytes. Experimental results show that all Nyquist impedance plots show depressed semicircies in the high-frequency range changing over into straight lines at lower frequencies. With increasing amounts of Cs(superscript +), the redox potentials in CV curves shift toward more positive values and the redox peaks broaden; the semicircle radius in corresponding EIS curves and the charge transfer resistance also increase. EIS combining CV is able to provide valuable insights into the ion selectivity of NiHCF thin films.

Curly hard carbon derived from pistachio shells as high-performance anode materials for sodium-ion batteries

Sodium-ion batteries (SIBs) have drawn more attention to serve as one of the promising energy storage devices owing to the abundance of sodium resources and similar characters with lithium element. Hard carbon materials derived from biomass or biomass waste have been considered to act as candidate anode materials for SIBs. In this paper, we have successfully prepared curly hard carbon materials using pistachio shells as biomass template via a two-step approach including hydrothermal treatment and following a pyrolysis process at various temperatures. Physical properties of pistachio shell-derived hard carbons (PSHCs) including microstructure, morphology and pore size distribution are evaluated by X-ray diffraction, Raman spectrum and N2 sorption analysis. The PSHCs carbonized at 1000xa0°C (PSHC-1000) with average micropores of 0.7398xa0nm and larger interlayer space of the (002) crystal plane deliver the highest reversible capacity of 317xa0mAhxa0g−1 at 0.1C, also show the excellent long-term cycling and rate performances. Electrochemical impedance spectroscopy technology is introduced to study the kinetics parameters during the first sodiation process of PSHC-1000 electrode, and also to compare the resistance of the charge transfer process for all the PSHCs. Results exhibit PSHC-1000 electrode with the symmetry factor of 0.1352 has the smallest charge transfer resistance, leading to more easily transportation of electrons and ions. This work can provide a simple and green route for preparation of hard carbon materials derived from biomass waste with unique morphology and microstructure which can exhibit an excellent electrochemical performance.

Performance evaluation of borohydride electrooxidation reaction with ternary alloy Au–Ni–Cu/C catalysts

Carbon-supported Au–Ni–Cu, Au–Ni, Au–Cu and Au nanoparticles were synthesised using a polyol reduction method. The prepared nanoparticle catalysts were used as anode electrocatalysts in direct borohydride–hydrogen peroxide fuel cells. The physical properties of the as-prepared electrocatalysts were studied using X-ray diffraction (XRD), and transmission electron microscopy (TEM). XRD and TEM analyses showed that the average size of the particles was approximately 10–20xa0nm. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were employed to analyse the borohydride oxidation reaction (BOR) on Au/C, Au–Cu/C, Au–Ni/C and Au–Ni–Cu/C. The results showed that the catalytic activity for BOR decreased in the order Au2–Ni1–Cu1/Cu2009>u2009Au1.5–Ni1–Cu1/Cu2009>u2009Au1–Ni1/Cu2009>u2009Au1–Cu1/Cu2009>u2009Au/C. Single-cell direct borohydride fuel cell (DBFC) tests also attested that the Au2–Ni1–Cu1/C anode catalyst exhibited better performance than the Au–Cu/C, Au–Ni/C and Au/C anode catalysts. Therefore, the ternary Au2–Ni1–Cu1/C catalyst can be a potential anode catalyst for DBFCs.Graphical Abstract

Preparation and Application of Multirow Graphite Cores NiHCF Film Electrodes for Electrochemically Controlled Cesium Separation

The electractive nickel hexacyanoferrate (NiHCF) thin films were synthesized on the multirow graphite substrates which were composed of 27 graphite cores by a cathodical deposition. The multirow graphite core electrodes were investigated as Electrochemically Controlled Ion Separation (ECIS) materials for the selective separation of cesium (Cs+). In the simulation solution containing Cs+, Cs+ are reversibly intercalated and deintercalated from the matrix by electrochemical modulation of the reduced and oxidized states of the film. This paper presents results of experiments on the development of a flow system for the Cs+ separation. Ion Chromatography (IC) was used to determine the effect of experimental conditions on the Cs+ selective separation for the NiHCF thin film, such as the initial [Cs+] concentration, surface state, regenerability, and flow velocity on the Cs+ selective separation for the NiHCF thin film .The experiment results show that the Cs+ entering into the NiHCF film in oxidized state increase with time. With increasing amounts of Cs+ in solution, the [Cs+] entering into NiHCF film are larger while in the corresponding solution the removing rate of Cs+ is also larger. It is demonstrated that the NiHCF film on the substrate of multiple sequential graphite cores have good ECIS performance and regenerability.