Narrow Pore Size Distribution Research Articles

Research progress and prospect of membrane method in seawater/brine extraction of lithium

With the widespread promotion of new energy electric vehicles for lithium batteries worldwide, the demand for lithium is surging. And the industry chain of lithium is in the process of technological transformation and upgrading, the extraction of lithium from salt lake brine is becoming the main source. Comprehensively compare the precipitation method, adsorption method, calcining leaching method, extraction method, and other processes used in the extraction of lithium from brine, membrane separation is a high-efficiency and energy-saving separation and purification technology without phase change at room temperature, and it has become the most promising energy-saving and environmentally-friendly new technology in the lithium extraction industry. At present, the research on membrane processes with lithium separation effect mainly includes membrane-adsorption, membrane-solvent extraction and membrane-electrodialysis, etc. And membrane-electrodialysis technology has been successfully applied to extract lithium from salt lake brine in industry. However, the existing shortcomings of organic membranes, such as membrane blockage, organic matter dissolution loss, and environmental pollution, limit the promotion of membrane-electrodialysis in the lithium extraction industry. Inorganic ceramic membranes are divided into microfiltration, ultrafiltration and nanofiltration according to the pore size. The separation process is mainly based on the “physical screening” theory, and the inorganic ceramic membrane material has stable chemical structure, good mechanical properties, simple preparation process, high temperature resistance, uniform pore size, It has many advantages such as narrow pore size distribution range and long life. Therefore, the development of new inorganic membrane materials has attracted widespread attention from the academic community and has become a hot issue in the study of lithium extraction by membrane methods.

Precise Sub-Angstrom Ion Separation Using Conjugated Microporous Polymer Membranes.

Polymer membranes typically possess a broad pore-size distribution that leads to much lower selectivity in ion separation when compared to membranes made of crystalline porous materials; however, they are highly desirable because of their easy processability and low cost. Herein, we demonstrate the fabrication of ion-sieving membranes based on a polycarbazole-type conjugated microporous polymer using an easy to scale-up electropolymerization strategy. The membranes exhibited high uniform sub-nanometer pores and a precisely tunable membrane thickness, yielding a high ion-sieving performance with a sub-1 Å size precision. Both experimental results and molecular simulations suggested that the impressive ion-sieving performance of the CMP membranes originates from their uniform and narrow pore-size distribution.

Geosmin and 2-methylisoborneol adsorption using different carbon materials: Isotherm, kinetic, multiple linear regression, and deep neural network modeling using a real drinking water source

High concentrations of geosmin (GSM) and 2-methylisoborneol (MIB) caused by cyanobacterial blooms are problematic issues in drinking water treatment plants on the Nak-Dong River in South Korea. The goal of this study was to identify the best-performing carbon materials to treat GSM and MIB in river water and to predict the final concentrations of GSM and MIB according to different water quality parameters using computational predictive modeling, multiple linear regression (MLR), and a deep neural network (DNN) for practical applications. Three types of powdered activated carbon (PAC) and three types of mesoporous carbon (MC) were compared in terms of their adsorption capacities using a source of drinking water from the Nak-Dong River. The highest maximum adsorption capacities were achieved when using C-PAC (1485.06 μg/g) in both distilled water and river water. C-PAC possesses a high micropore volume (0.45 cm3/g), low mesopore volume (0.11 cm3/g), and small, narrow pore size distribution, yielding optimal adsorption conditions. PACs yielded better results than MCs because dominant mesopore structures can hinder the adsorption of small molecules (0.6–0.8 nm) and allow them to pass through pores. GSM was removed more effectively than MIB because GSM is more hydrophobic and has a flatter structure. The high dissolved organic carbon concentration in the river water caused no reduction in GSM and MIB adsorption, but actually enhanced adsorption because a small portion of natural organic matter can compete with adsorption sites and provide additional adsorption sites based on the shrunk pore effect. The MLR and DNN models were used to predict the removal efficiency of C-PAC for GSM and MIB using 72 individual datasets with cross-validation for robust prediction and sensitivity analysis. MLR predicted the relationships between the input variables and GSM and MIB concentrations with an acceptable mean absolute error (MAE) of 6.43 ng/L for GSM and 5.80 ng/L for MIB. However, the DNN provided better agreement with a higher R2 value (>0.99) and lower MAE of 1.67 ng/L for GSM and 1.24 ng/L for MIB.

Tunable Pore Size from Sub-Nanometer to a Few Nanometers in Large-Area Graphene Nanoporous Atomically Thin Membranes.

Membranes are key components in chemical purification, biological separation, and water desalination. Traditional polymeric membranes are subjected to a ubiquitous trade-off between permeance and selectivity, which significantly hinders the separation performance. Nanoporous atomically thin membranes (NATMs), such as graphene NATMs, have the potential to break this trade-off. Owing to their uniqueness of two-dimensional structure and potential nanopore structure controllability, NATMs are expected to have outstanding selectivity through molecular sieving while achieving ultimate permeance at the same time. However, a drastic selectivity discrepancy exists between the proof-of-concept demonstrations and scalable separation applications in graphene membranes. In this paper, we offer a possible solution to narrow this discrepancy by tuning the pore density and pore size separately with two successive plasma treatments. We demonstrate that by narrowing the pore size distribution, the selectivity of graphene membranes can be greatly increased. Low-energy argon plasma is first applied to nucleate high density of defects in graphene. Controlled oxygen plasma is then utilized to selectively enlarge the defects into nanopores with desired sizes. This method is scalable, and the fabricated 1 cm2 graphene NATMs with sub-nanometer pores can separate KCl and Allura Red with a selectivity of 104 and a permeance of 1.1 × 10-6 m s-1. The pores in NATMs can be further tuned from gas-selective sub-nanometer pores to a few nanometer size. The fabricated NATMs show a selectivity of 35 between CO2 and N2. With longer enlargement time, a selectivity of 21.2 between a lysozyme and bovine serum albumin can also be achieved with roughly four times higher permeance than that of a commercial dialysis membrane. This research offers a solution to realize NATMs of tunable pore size with a narrow pore size distribution for different separation processes from sub-nanometer in gas separation or desalination to a few nanometers in dialysis.

Etched ion-track membranes as tailored separators in Li–S batteries

Lithium–sulfur (Li–S) batteries are considered a promising next generation alternative to lithium-ion batteries for energy storage systems due to its high energy density. However, several challenges, such as the polysulfide redox shuttle causing self-discharge of the battery, remain unresolved. In this paper, we explore the use of polymer etched ion-track membranes as separators in Li–S batteries to mitigate the redox shuttle effect. Compared to commercial separators, their unique advantages lie in their very narrow pore size distribution, and the possibility to tailor and optimize the density, geometry, and diameter of the nanopores in an independent manner. Various polyethylene terephthalate membranes with diameters between 22 and 198 nm and different porosities were successfully integrated into Li–S coin cells. The reported coulombic efficiency of up to 97% with minor reduction in capacity opens a pathway to potentially address the polysulfide redox shuttle in Li–S batteries using tailored membranes.

Effect of surface morphology on the mesoporous silicon modified nanofiltration membranes for high rejection performance

A new method to prepare composite nanofiltration membrane directly and efficiently by controlling the pore structure and surface morphology of the membrane is proposed in this paper. The fabrication of mesoporous silicon modified polysulfone blend membranes is via a phase inversion method. The structural morphology, surface functional group analysis, elemental analysis, hydrophilicity, chargeability, and nitrogen pollutant (ammonia nitrogen, nitrate nitrogen, total nitrogen) rejection properties of the modified membranes were found to be dependent on the amount of mesoporous silicon incorporated. The combination of the mesoporous silicon framework layer can not only effectively improve the surface structure of the modified membrane with a narrow pore size distribution but also increase the rejection of nitrogen pollutant compared with the pure NF membranes. The mesoporous material can absorb and storage the nitrogenous solution to facilitate the following interfacial polymerization, as well as induce the change of pore radius and surface structure. Compared to those pure NF composite membranes, the modified blend membranes exhibit increased water permeation flux as high as 29.09 L m−2 h−1 at 0.2 MPa. The results show that the optimum doping amount of mesoporous silicon is in the range of 0.5%-1.0%. Characterization studies demonstrated that the addition of the mesoporous silicon leads to decreased membrane pore size. Then, due to the enhanced hydrophilicity of carboxyl and hydroxyl groups on the surface, the electrostatic repulsion between the functional groups and nitrogen pollutant molecules in the membrane results in the enhanced rejection of nitrogen pollutants.

Modification of porous polyetherimide hollow fiber membrane by dip-coating of Zonyl® BA for membrane distillation of dyeing wastewater.

Wetting and fouling have significantly affected the application of membrane distillation (MD). In this work, a dip-coating method was used for improving surface hydrophobicity of the polyetherimide (PEI) hollow fiber membrane. An air gap membrane distillation (AGMD) process was applied for treatment of the methylene blue (MB) solution. The porous PEI membrane was fabricated by a dry-wet spinning process and the hydrophobic 2-(Perfluoroalkyl) ethanol (Zonyl® BA) was used as the coating material. From FESEM, the modified PEI-Zonyl membrane showed an open structure with large finger-like cavities. The modified membrane displayed a narrow pore size distribution with mean pore size of 0.028 μm. The outer surface contact angle of the PEI-Zonyl membrane increased from 81.3° to 100.4° due to the formation of an ultra-thin coated layer. The pure water flux of the PEI-Zonyl membrane was slightly reduced compared to the pristine PEI membrane. A permeate flux of 6.5 kg/m2 h and MB rejection of 98% were found for the PEI-Zonyl membrane during 76 h of the AGMD operation. Adsorption of MB on the membrane surface was confirmed based on the Langmuir isotherm evaluation, AFM and FESEM analysis. The modified PEI-Zonyl membrane can be a favorable alternative for AGMD of dyeing wastewaters.

Fabrication and Characterization of Hydrophobic PVDF-based Hollow Fiber Membranes for Vacuum Membrane Distillation of Seawater and Desalination Brine

Fabrication of hydrophobic polyvinylidene fluoride (PVDF) hollow fiber membranes was studied using Lithium chloride (LiCl) and polyethylene glycol (PEG) 35000 as non-solvent additives by dry-wet phase inversion process. Scanning Electron Microscopy revealed that LiCl addition made the finger-like voids become smaller and provided a sponge-like structure, in addition to increasing the membrane surface roughness to 42 nm, porosity to 83% and mean pore size to 5.75 nm with narrower pore size distribution. It also decreased Young's modulus to 63 MPa while, no significant improvement was observed in water contact angle (115.5o). During vacuum membrane distillation (VMD) of water, Mediterranean Sea water, Red Sea water and Red Sea brine, the PVDF membranes spun with LiCl achieved higher water permeation flux with values of 48, 32, 25 and 19 L/m2h, respectively. The flux-salinity relationship was represented by empirical correlations. The two membranes exhibited high salt rejection values (99.4%-99.8%) for the investigated saline solutions. These results suggest numerous interventions for membrane distillation within integrated desalination/salt recovery schemes or as a stand-alone facility with the combination of complementary appropriate thermal crystallization units. Two VMD/solar pond scenarios were investigated for dual production of water and salts.

Enhanced Photodegradation of p-Nitrobenzoic Acid by Binary Mixtures with Ba2+/TiO2 and MCM-41.

A novel Ba(II)/TiO2–MCM-41 composite was synthesized using binary mixtures with Ba2+/TiO2 and MCM-41, and Ba2+ as a doping ion of TiO2. The specific surface area and pore structure characterizations confirm that a mesoporous structure with a surface area of 341.2 m2/g and a narrow pore size distribution ranging from 2 to 4 nm was achieved using Ba(II)/TiO2–MCM-41. Ba(II)/TiO2 particles were synthesized into 10–15 nm particles and were well dispersed onto MCM-41. The diffraction peaks in the XRD patterns of TiO2–MCM-41 and Ba(II)/TiO2–MCM-41 were all attributed to anatase TiO2. By taking advantage of MCM-41 and Ba2+, the photocatalytic performance of Ba(II)/TiO2–MCM-41 was remarkably enhanced by suppressing its rutile phase, by lowering the band gap energy, and by facilitating the dispersion of TiO2. Therefore, the photodegradation efficiencies of p-nitrobenzoic acid (4 × 10−4 mol/L) by various photocatalysts (60 min) under UV light irradiation are arranged in the following order: Ba(II)/TiO2–MCM-41 (91.7%) > P25 (86.3%) > TiO2–MCM-41 (80.6%) > Ba(II)/TiO2 (55.7%) > TiO2 (53.9%). The Ba(II)/TiO2–MCM-41 composite was reused for five cycles and maintained a high catalytic activity (73%).

Direct foaming of Al2O3-based macroporous ceramics containing pre-foamed colloidal alumina, calcite and CAC suspension

Adding pre-foamed colloidal alumina to ultrastable Al2O3-stabilised foams can be a path towards partially counteracting the firing shrinkage of these materials and producing macroporous ceramics with smaller pores. Nevertheless, this system still presents a long setting time and high sintering-induced shrinkage, which hinders the production of larger samples and reduces its porosity. In the present work, it was observed that adding calcium aluminate cement suspension (CACS) and CaCO3 (calcite) to the aforementioned system can speed up its solidification kinetics, improve its mechanical strength and reduce its shrinkage after firing, maintaining high porosity and smaller pore sizes. By using these raw materials, samples with an average pore size below 60 μm, total porosity above 70%, and a narrower pore size distribution were attained after thermal treatment at 1600 °C for 5h. Moreover, due to the in situ formation of calcium hexaluminate, their shrinkage after sintering was almost halved (from ~20% to 11%).

Ultramicroporous carbon granules with narrow pore size distribution for efficient CH4 separation from coal‐bed gases

AbstractThe adsorptive separation of CH4 from low‐grade coal‐bed gas can be performed at decentralized and remote coal mines, and it uses more energy‐ and is cost‐efficient than the traditional cryogenic distillation process. Herein, we present a facile method to prepare ultramicroporous carbon granules with a narrow pore‐size distribution at 0.5–0.6 nm. To our knowledge, such centered and uniform pore‐size distribution in carbon granules has never been reported. The carbon granules can be directly utilized in adsorption columns without a granulation or pelletization process. The granular oil‐tea‐shell‐derived porous carbon (GOC‐2) exhibited a record‐high CH4 uptake of 1.82 mmol/g and CH4/N2 selectivity of 5.8 at 1.0 bar and 298 K among carbon granules. The excellent CH4/N2 separation performances were confirmed from the results of dynamic breakthrough experiments and pressure swing adsorption simulations. This work provides a novel strategy for developing ultramicroporous carbon granules and guides the future design of efficient CH4/N2 separation adsorbents.

Effective and efficient fabrication of high-flux tight ZrO2 ultrafiltration membranes using a nanocrystalline precursor

The use of membrane technology in protein purification is limited by the subsequent membrane fouling. In this study, tight ZrO2 ultrafiltration (UF) membranes with narrow pore size distributions, which effectively reduced the pollution of ceramic membranes, were prepared using a nanocrystalline precursor. The pore size distribution and permeance of the fabricated membranes were controlled by adjusting the sintering temperature. The molecular weight cut-off of the membranes increased from 25 kDa (7 nm) to 66 kDa (10.9 nm) as the sintering temperature increased from 400 °C to 800 °C, while their permeance increased from 135 to 225 L m−2 h−1 bar−1. The ZrO2 UF membrane sintered at the range of 400–600 °C was tested for the BSA molecules solution separation, which showed almost 100% of BSA molecules retention and demonstrated a stable permeance of approximately 80–95 L m−2·h−1 bar−1. Moreover, the sintering temperature of 500 °C was identified as the optimal temperature in terms of the removal of organic additives and energy consumption. The obtained results indicate that the prepared ZrO2 UF membranes can be potentially used for protein separation.

Synthesis of high-performance conjugated microporous polymer/TiO2 photocatalytic antibacterial nanocomposites

High-performance conjugated microporous polymer (CMP)/TiO2 photocatalytic antibacterial nanocomposites were successfully synthesized by in situ Sonogashira polymerization. TiO2 was uniformly dispersed onto the surface and within the CMP which show the microporous nature with narrow pore size distribution. The high crystallinity and thermal stability of the CMP/TiO2 nanocomposites are attractive for use as antibacterial materials. The composites we prepared showed excellent photocatalytic antibacterial properties for the inactivation of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) under visible light irradiation. The photocatalytic antibacterial rates of nanocomposites against E. coli and S. aureus after 120 min of visible light irradiation were 98.14% and 100%, respectively. The superoxide anion (O2−) was confirmed to be an important substance in the antibacterial process above. The cytocompatibility of the antibacterial agents was studied in terms of cytotoxicity against NIH 3T3 fibroblasts. More than 95% of the cells were still alive in the presence of the nanocomposites, both without and with light irradiation, indicating the good cytocompatibility of the nanocomposites. Judging from the excellent photocatalytic antibacterial properties and ultralow toxicity of nanocomposites, these materials can be used in many fields such as medical treatment, transportation and construction.

Preparation and characterization of asymmetric hollow fiber polyvinyl chloride (PVC) membrane for forward osmosis application

• Asymmetric nanofiltration PVC hollow fiber membranes were fabricated via dry-wet spinning technique. • Delayed demixing was achieved by addition of high molecular weigh PVP. • Volatile solvent evaporation resulted in dense selective layer. • The effect of fabrication parameters were investigated in order to introduce best-suited membrane. • The effect of DS concentration and temperature were studied by means of Flux and SRSF. PVC hollow fiber (HF) membrane for forward osmosis (FO) application as a potential candidate for water desalination was fabricated by altering the spinning conditions. High molecular weight polyvinylpyrrolidone (PVP) was used as a blending additive to control the phase inversion process by increasing viscosity leading to delayed demixing as observed on the ternary phase diagram and confirmed by the simulation results, and forming dense barrier layer structure by providing chain entanglements with the PVC matrix. PVP/PVC ratio of 5/100 was proved to offer suited membrane morphology and selective layer. Different air gap distances and bore fluid flow rates were investigated to achieve proper fabrication parameters. The prepared membranes presented high flux and salt rejection in nanofiltration (NF) and FO tests. The best-suited membrane demonstrated the structural parameter of 389 µm with a narrow pore size distribution and a molecular weight cut-off of 490 Da. In different draw solution (DS) concentrations, it was observed that the membranes perform well in all conditions. Considering the PVC-PVP chain entanglements and mobility and the possibility of PVP being washed away, the membranes’ performance at different temperatures indicated that 25–45 °C would be the safe operating range for the fabricated membranes with stable values of 31.0–33.4 LMH and 0.17–0.18 (FO mode) and 33.0–33.4 LMH and 0.23–0.24 (PRO mode) for water flux and specific reverse salt flux.

Microporous formation and evolution mechanism of PTFE fibers/isotactic polypropylene membranes by interface separation

Studying microporous formation and evolution mechanism plays a crucial role in fabricating high-performance microporous membranes. A formation mechanism of PP microporous membranes, different from those reported previously, was proposed based on the interface separation of PTFE fibers and PP matrix during sequential biaxial stretching. The experimental results indicated that the initial microcracks, which were filled by microfibrillated PP, were originated from PTFE fibers-PP matrix interfaces perpendicular to the longitudinal stretching direction. As the strain increased, microfibrillated PP was further elongated, ultimately forming microfibrillated PP membranes at a relatively low strain (200%). The subsequent transverse stretching caused the separation of fibrillated PP to form an excellent microporous structure. As a result, PTFE/PP membranes after biaxial stretching exhibited the narrower pore size distribution, higher porosity, higher N2 flux and pure water flux than β-PP membranes.

Ultrahigh Hydrogen Uptake in an Interpenetrated Zn 4 O-Based Metal–Organic Framework

As a highly promising candidate for hydrogen storage, crucial to vehicles powered by fuel cells, metal–organic frameworks (MOFs) have attracted the attention of chemists in recent decades. H2 uptak...

A novel gas diffusion layer and its application to direct methanol fuel cells

The gas diffusion layer (GDL) is an important component of the membrane electrode assembly of fuel cells (FCs). Its roles include supporting the catalyst layer, collecting current, and transferring and redistributing materials. A conventional GDL consists of a backing layer, typically of commercial carbon paper or carbon cloth, but it suffers from its high cost, narrow pore-size distribution, lack of flexibility and poor conductivity, and a micro-porous layer (MPL) is necessary for better gas/liquid management. A novel flexible gas diffusion layer (GDL) was prepared by vacuum filtration of a suspension of carbon fibers (CFs) and highly-dispersed multi-wall carbon nanotubes (MWCNTs) in a polytetrafluoroethylene (PTFE) binder and water repellent. SEM observations, gas permeability and porosity tests indicate that there is a gradient in the concentration of highly-conductive MWCNTs in the CNT-CF GDL network that facilitates electron transport. A multi-level pore structure is formed, which is beneficial to mass transport. The PTFE is distributed uniformly, which is favorable for the discharge of condensed water from the FCs. When the GDL/CNT-CF is used in the cathode, or in both the cathode and anode in direct methanol FCs, the maximum power densities of single cells are increased by 20% and 35%, respectively, compared with those using a commercial GDL consisting of carbon paper with a MPL due to its excellent mass transfer performance.

Adsorption Property of Starch-Based Microporous Carbon Materials with High Selectivity and Uptake for C1/C2/C3 Separation

Recovering light hydrocarbons from natural gas is of great significance in the petrochemical industry. In this work, starch-based microporous carbon materials (SMCs) were prepared using starch as a carbon source and characterized for their pore structure and surface chemistry. CH4, C2H6, and C3H8 isotherms of SMCs were determined using a volumetric method. The breakthrough experiments were carried out to evaluate the dynamic separation performance. A grand canonical Monte Carlo simulation was conducted to reveal the adsorption mechanism of these light hydrocarbons on the SMCs. Results showed that the resulting SMCs exhibited a high specific surface area of 1999 m2/g and a narrow pore size distribution within 0.5–2.0 nm. Particularly, SMCs displayed extremely high ethane and propane uptakes at 298 K and 100 kPa, reaching 5.28 mmol/g for C2H6 and 8.39 mmol/g for C3H8. Moreover, SMCs showed an ultrahigh selectivity of 27.1 for C2H6/CH4 mixtures under ambient conditions, which exceeded that of many metal–organic frameworks. Thus, SMCs have the potential for recovering light hydrocarbons from natural gas.

Role of NO and SO2 in mercury oxidation over a La2O3/Fe2O3 catalyst with high thermal stability

In this study, the thermal stability of a ferric oxide catalyst for mercury oxidation was found to be considerably promoted by doping with La2O3. The catalysts doped with La2O3 maintained a higher surface area when subjected to high-temperature calcination, with lower average pore size and a narrower pore size distribution. X-ray diffraction (XRD) results revealed that La2O3 doping hinders the growth of catalyst particles and crystallization of the material at high temperatures. Both NO and SO2 inhibited Hg0 oxidation over the La2O3/Fe2O3 catalyst. Fourier transform infrared (FTIR) spectra revealed that SO2 reacts with O2 over the catalysts to form several species that are inert for mercury oxidation, such as SO42−, HSO4−, or other related species; these inert species cover the catalyst surface and consequently decrease Hg0 oxidation capacity. In addition, NO or SO2 competed with Hg0 for active sites on the La2O3/Fe2O3 catalyst and hindered the adsorption of mercury, thereby inhibiting subsequent Hg0 oxidation. Hg0 oxidation on the La2O3/Fe2O3 catalyst mainly followed the Eley–Rideal mechanism. Moreover, the inhibition effects of NO and SO2 were at least partially reversible, and the catalytic activity was temporarily restored after eliminating NO or SO2.

FacileSynthesis of Anatase TiO2Nanocrystals with Co‐Exposed{101}, {010}/{100} and [111]‐Facets for EfficientPhotodegradation of Methylene Blue

AbstractCuboid‐shaped anatase TiO2 nanocrystals with co‐exposed {101} and [111]‐facets (or {101} and {100} facets), diamond‐shaped, rod‐like and irregular anatase TiO2 nanocrystals with dominant {010} facets were controllably synthesized from titanium (IV) ethoxide (TEOT) using HF as a capping agent via a facile sol‐gel procedure, and characterized by X‐ray powderdiffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), nitrogen adsorption, photoluminescence (PL) spectra, UV‐vis diffuse reflectance spectra,and electrochemical impedance spectroscopy (EIS). For the as‐prepared anatase TiO2 nanocrystals, the 0.5HF‐TiO2 revealed the best photocatalytic efficiency under UV light irradiation: 94.1 % of methylene blue (MB) was photodegraded within 90 min. The reaction rate constant k(min−1) was 1.39, 1.47, 1.59, 1.66, 1.92, 2.75, and 30.5 times higher than that of 2.0HF‐TiO2 (2.20×10−2 min−1), 1.5HF‐TiO2 (2.07×10−2 min−1), 1.0HF‐TiO2 (1.92×10−2 min−1), 2.5HF‐TiO2 (1.84×10−2 min−1), 3.0HF‐TiO2 (1.59×10−2 min−1), Bodi‐TiO2 (1.11×10−2 min−1), and the blank sample (0.10×10−2 min−1), respectively. Compared to other as‐prepared anatase TiO2 nanocrystals with the similar co‐exposed crystal facets, the highest efficiency of 0.5HF‐TiO2 could be attributed to the minimum crystal size,narrower pore size distribution, the maximum specific surface area, the lowest PL intensity and charge‐transfer resistance, andthe smallestrecombination resistance.