Opportunity and challenges in recovering and functionalizing anode graphite from spent lithium-ion batteries: A review.

Recent concerns have emerged regarding the improper disposal of spent lithium-ion batteries (LIBs), which has garnered widespread societal attention. Graphite materials accounted for 12-21 wt % of LIBs' mass, typically contain heavy metals, binders, and residual electrolytes. Regenerating spent graphite not only alleviated the shortage of plumbago, but also contributed to the supports environmental protection as well as national carbon peak and neutrality ("dual carbon" goals). Despite significant advancements in recycling spent LIBs had been made, a comprehensive overview of the processes for pretreatment, regeneration, and functionalization of spent graphite from retired LIBs, along with the associated technical standards and industry regulations enabling their smooth implementation still needed to be mentioned. Hence, we conducted the following research work. Firstly, the pre-treatment process of spent graphite, including discharging, crushing, and screening was summed up. Next,. Subsequently, graphite recovery methods, such as acid leaching, pyrometallurgy, and combined methods were summarized. Moreover, the modification and doping approach was used to enhance the electrochemical properties of graphite. Afterwards, we reviewed the functionalization of anode graphite from an economically and environmentally friendly view. Meanwhile, the technical standards and industry regulations of spent LIBs in domestic and oversea industries were described. Finally, we provided an overview of the technical challenges and development bottlenecks in graphite recycling, along with future prospects Overall, this study outlined the opportunities and challenges in recovering and functionalizing of anode materials via a efficient and sustainable processes.

Study of the Adsorption Behavior of Surfactants on Carbonate Surface by Experiment and Molecular Dynamics Simulation.

Surfactants adsorption onto carbonate reservoirs would cause surfactants concentrations decrease in surfactant flooding, which would decrease surfactant efficiency in practical applications of enhanced oil recovery (EOR) processes. Different surfactants could be classified as cationic surfactants, anionic surfactants, non-ionic surfactants according to the main charge, or be classified as chemical surfactant and bio-surfactant according to the surfactant origin. However, the research on different type surfactants adsorption on carbonate reservoirs surface differences was few. Therefore, five representative surfactants (CTAB, SDS, TX-100, sophorolipid, rhamonilipid) adsorption effect onto carbonate reservoirs surface was studied. Owing to the fact that the salinity and temperature in underground carbonate reservoirs were high during the EOR process, it is vital to study the salinity effect and temperature effect on surfactant adsorption. In this study, different surfactants species, temperature and salinity adsorption onto carbonate reservoirs were studied. The adsorption isotherms were fitted by Langmuir, Freundlich, Temkin and Linear models, and the first three models fitting effect were good. The results showed that cationic surfactants adsorption quantity was higher than anionic surfactants, and the non-ionic surfactants adsorption quantity was the lowest. When the temperature increased, the surfactants adsorption would decrease, because the adsorption process was exothermic process, and increasing temperature would inhibit the adsorption. The higher salinity would increase surfactants adsorption because higher salinity could compress electric double layer. In order to decrease surfactants adsorption, SiO2 nanoparticles and TiO2 nanoparticles were added to surfactants solutions, and then surfactants could adsorb onto nanoparticles surface, then the steric hindrance between surfactant molecules would increase, which could decrease surfactants adsorption. Contact angle results indicated that surfactants adsorption made the carbonate reservoir wettability alteration. In the end, surfactants (with or without SiO2 nanoparticles) adsorption onto carbonate reservoirs mechanism were studied by molecular dynamics simulation. The simulation results indicated that the surfactants molecules could adsorb onto SiO2 nanoparticles surface, and then the surfactants adsorption quantity onto carbonate rocks would decrease, which was in accordance with the experiments results.

High-performance BiVO4 photoanodes cocatalyzed with bilayer metal-organic frameworks for photoelectrochemical application.

In this work, we modified a BiVO4 photoanode with bilayer Fe-MOF and Ni-MOF as cocatalysts for the first time and obtained a highly efficient BiVO4 composite photoanode whose photocurrent density was increased by 2.7 times. The optimized BiVO4/Fe-MOF/Ni-MOF photoanode demonstrated a photocurrent density of 1.80 mA/cm2 at 1.23 V vs. a reversible hydrogen electrode (RHE). The onset potential of the BiVO4/Fe-MOF/Ni-MOF photoanode markedly decreased from 0.9 V to 0.69 V in comparison with the pure BiVO4 photoanode. It is speculated that Fe-MOF and Ni-MOF led to more reactive oxygen evolution sites and that the bilayer cocatalysts synergistically promoted the separation of photogenerated electron-hole pairs, which may be the influencing factor for the photoelectrochemical performance of the BiVO4/Fe-MOF/Ni-MOF photoanode being distinctively enhanced. Thus, this work sheds some interesting new light on the construction of a high-efficiency photoanode for photoelectrochemical applications.

Enhanced reactive oxygen species via in situ producing H2O2 and synchronous catalytic conversion at stable modified copper foam cathode for efficient high-concentration organic wastewater treatment and simultaneous electricity generation.

Efficient high-concentration organics degradation (including 2-CP, phenol, and tetracycline) and simultaneous electricity generation were achieved via in situ producing H2O2 and synchronous catalytic conversion to more reactive oxygen species at stable modified copper foam cathode. The cathode was synthesized using the one-pot electrodeposition method and was used to in-situ generate H2O2 through the two-electron reduction of oxygen. The produced H2O2 was then catalytically converted into ·OH and ·O2- simultaneously. The results showed that the system using the Au-Fe co-modified cathode achieved an optimal rhodamine b (50 mg L-1) removal ratio and the removal ratios of 2-CP, phenol and tetracycline were all higher than 90% in 120 min. Meanwhile, it exhibited a high conversion performance of organics into electricity, which is superior to most of the reported PFC (Photocatalytic Fuel Cell) systems. Electron spin resonance test was conducted to ascertain the role of ·O2- and ·OH in the organics degradation. Furthermore, the Au-Fe-modified cathode exhibited superior stability for long-term application in the pH range of 3-7, which can be attributed to the protection of photocurrent and the interaction between Cu and Fe.

Photocatalytic nitrogen fixation: Oxygen vacancy modified novel micro-nanosheet structure Bi2O2CO3 with band gap engineering.

As a promising ammonia synthesis approach to replace the industrial Harber method, the biggest problem restricting photocatalytic nitrogen fixation is the suboptimal efficiency. Herein, novel surface oxygen vacancies modified micro-nanosheet structure Bi2O2CO3 (namely BOC/OV) were successfully synthesized via facile formation under room temperature. These defects-rich nanosheets exhibit outstanding performance for photocatalytic nitrogen fixation under visible light. The surface oxygen vacancies provide abundant active sites for molecular N2 activation, and the effect of scattered nanometer-size could facilitate the separation of photo-generated charges. Moreover, the energy band can be consecutively tuned with the accumulation of surface oxygen vacancies by lowering the conduction band position. Among all as-prepared samples, BOC/OV3 exhibited the highest NH4+ yield, reaching 1178 µmol·L-1·g-1·h-1, which is 10 times than that of pristine Bi2O2CO3. In this work, all samples synthesis and defects formation were conducted without requiring any secondary energy, which is of great significance for realizing green and efficient artificial ammonia synthesis.

Enhanced Photocatalytic Activity toward Organic Pollutants Degradation and Mechanism Insight of Novel CQDs/Bi2O2CO3 Composite.

Novel carbon quantum dots (CQDs) modified with Bi2O2CO3 (CQDs/Bi2O2CO3) were prepared using a simple dynamic-adsorption precipitation method. X-ray diffractometry (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) were used to test the material composition, structure, and band structures of the as-prepared samples. Methylene blue (MB) and colorless phenol, as target organic pollutants, were used to evaluate the photocatalytic performance of the CQDs/Bi2O2CO3 hybrid materials under visible light irradiation. Experimental investigation shows that 2⁻5 nm CQDs were uniformly decorated on the surface of Bi2O2CO3; CQDs/Bi2O2CO3 possess an efficient photocatalytic performance, and the organic matter removal rate of methylene blue and phenol can reach up to 94.45% and 61.46% respectively, within 2 h. In addition, the degradation analysis of phenol by high performance liquid chromatography (HPLC) proved that there are no other impurities in the degradation process. Photoelectrochemical testing proved that the introduction of CQDs (electron acceptor) effectively suppresses the recombination of e--h⁺, and promotes charge transfer. Quenching experiments and electron spin resonance (ESR) suggested that ·OH, h⁺, and ·O2- were involved in the photocatalytic degradation process. These results suggested that the up-conversion function of CQDs could improve the electron transfer and light absorption ability of photocatalysts and ·O2- formation. Furthermore, the up-conversion function of CQDs would help maintain photocatalytic stability. Finally, the photocatalytic degradation mechanism was proposed according to the above experimental result.

Oil-in-Water Self-Assembled Synthesis of Ag@AgCl Nano-Particles on Flower-like Bi2O2CO3 with Enhanced Visible-Light-Driven Photocatalytic Activity.

In this work, a series of novel flower-like Ag@AgCl/Bi2O2CO3 were prepared by simple and feasible oil-in-water self-assembly processes. The phase structures of as-prepared samples were examined by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), X-ray fluorescence spectrometer (XRF), etc. The characterization results indicated that the presence of Ag@AgCl did not affect the crystal structure, but exerted a great influence on the photocatalytic activity of Bi2O2CO3 and enhanced the absorption band of pure Bi2O2CO3. The photocatalytic activities of the Ag@AgCl/Bi2O2CO3 samples were determined by photocatalytic degradation of methylene blue (MB) under visible light irradiation. The Ag@AgCl (10 wt %)/Bi2O2CO3 composite showed the highest photocatalytic activity, degrading 97.9% MB after irradiation for 20 min, which is over 1.64 and 3.66 times faster than that of pure Ag@AgCl (calculated based on the equivalent Ag@AgCl content in Ag@AgCl (10 wt %)/Bi2O2CO3) and pure Bi2O2CO3, respectively. Bisphenol A (BPA) was also degraded to further prove the degradation ability of Ag@AgCl/Bi2O2CO3. Photocurrent studies indicated that the recombination of photo-generated electron-hole pairs was decreased effectively due to the formation of heterojunctions between flower-like Bi2O2CO3 and Ag@AgCl nanoparticles. Trapping experiments indicated that O2-, h⁺ and Cl° acted as the main reactive species for MB degradation in the present photocatalytic system. Furthermore, the cycling experiments revealed the good stability of Ag@AgCl/Bi2O2CO3 composites. Based on the above, a photocatalytic mechanism for the degradation of organic compounds over Ag@AgCl/Bi2O2CO3 was proposed.

Enhanced Visible Light Photocatalytic Degradation of Organic Pollutants over Flower-Like Bi2O2CO3 Dotted with Ag@AgBr.

A facile and feasible oil-in-water self-assembly approach was developed to synthesize flower-like Ag@AgBr/Bi2O2CO3 micro-composites. The photocatalytic activities of the samples were evaluated through methylene blue degradation under visible light irradiation. Compared to Bi2O2CO3, flower-like Ag@AgBr/Bi2O2CO3 micro-composites show enhanced photocatalytic activities. In addition, results indicate that both the physicochemical properties and associated photocatalytic activities of Ag@AgBr/Bi2O2CO3 composites are shown to be dependent on the loading quantity of Ag@AgBr. The highest photocatalytic performance was achieved at 7 wt % Ag@AgBr, degrading 95.18% methylene blue (MB) after 20 min of irradiation, which is over 1.52 and 3.56 times more efficient than that of pure Ag@AgBr and pure Bi2O2CO3, respectively. Bisphenol A (BPA) was also degraded to further demonstrate the degradation ability of Ag@AgBr/Bi2O2CO3. A photocatalytic mechanism for the degradation of organic compounds over Ag@AgBr/Bi2O2CO3 was proposed. Results from this study illustrate an entirely new approach to fabricate semiconductor composites containing Ag@AgX/bismuth (X = a halogen).