Oxygen vacancy （Ov） has significant influence on physical and chemical properties of TiO2 systems, especially on surface catalytic processes. In this work, we investigate the effects of Ov on the adsorption of forma...Oxygen vacancy （Ov） has significant influence on physical and chemical properties of TiO2 systems, especially on surface catalytic processes. In this work, we investigate the effects of Ov on the adsorption of formaldehyde （HCHO） on TiO2（110） surfaces through first- principles calculations. With the existence of Ov, we find the spatial distribution of surface excess charge can change the relative stability of various adsorption configurations. In this case, the bidentate adsorption at five-coordinated Ti （Tisc） can be less stable than the monodentate adsorption. And HCHO adsorbed in Ov becomes the most stable structure. These results are in good agreement with experimental observations, which reconcile the long-standing deviation between the theoretical prediction and experimental results. This work brings insights into how the excess charge affects the molecule adsorption on metal oxide surface.展开更多
Catalytic elimination of formaldehyde(HCHO) was investigated over Cu-Al_2O_3 catalyst at room temperature. The results indicated that no oxidation of HCHO into CO_2 occurs at room temperature, but the adsorption of H...Catalytic elimination of formaldehyde(HCHO) was investigated over Cu-Al_2O_3 catalyst at room temperature. The results indicated that no oxidation of HCHO into CO_2 occurs at room temperature, but the adsorption of HCHO occurs on the catalyst surface. With the increase of gas hourly space velocity(GHSV) and inlet HCHO concentration, the time to reach saturation was shortened proportionally. The results of the in situ DRIFTS, Density functional theory calculations and temperature programmed desorption(TPD) showed that HCHO was completely oxidized into HCOOH over Cu-Al_2O_3 at room temperature. With increasing the temperature in a flow of helium, HCOOH was completely decomposed into CO_2 over the catalyst surface, and the deactivated Cu-Al_2O_3 is regenerated at the same time. In addition, although Cu had no obvious influence on the adsorption of HCHO on Al_2O_3, Cu dramatically lowered the decomposition temperature of HCOOH into CO_2. It was shown that Cu-Al_2O_3 catalyst had a good ability for the removal of HCHO, and appeared to be promising for its application in destroying HCHO at room temperature.展开更多
The degradation of formaldehyde gas was studied using UV/TiO2/O3 process under the condition of continuous flow mode. The effects of humidity, initial formaldehyde concentration, residence time and ozone adding amount...The degradation of formaldehyde gas was studied using UV/TiO2/O3 process under the condition of continuous flow mode. The effects of humidity, initial formaldehyde concentration, residence time and ozone adding amount on degradation of formaldehyde gas were investigated. The experimental results indicated that the combination of ozonation with photocatalytic oxidation on the degradation of formaldehyde showed a synergetic action, e.g,, it could considerably increase decomposing of formaldehyde. The degradation efficiency of formaldehyde was between 73.6% and 79.4% while the initial concentration in the range of 1.84--24 mg/m^3 by O3/TiO2flJV process. The optimal humidity was about 50% in UV/TiO2/O3 processs and degradation of formaldehyde increases from 39.0% to 94.1% when the ozone content increased from 0 to 141 mg/m^3. Furthermore, the kinetics of formaldehyde degradation reaction could be described by Langmuir-Hinshelwood model. The rate constant k of 46.72 mg/（m^3.min） and Langmuir adsorption coefficient K of 0.0268 m^3/mg were obtained.展开更多
Powder quartz(PQ)/nano-TiO2composite was prepared by a mechanochemical method. Based on as-prepared PQ/nano-TiO2composite, we prepared interior paints and investigated the degradation efficiency of formaldehyde(DEF). ...Powder quartz(PQ)/nano-TiO2composite was prepared by a mechanochemical method. Based on as-prepared PQ/nano-TiO2composite, we prepared interior paints and investigated the degradation efficiency of formaldehyde(DEF). Scanning electron microscopy showed that nano-TiO2got well dispersed by the adding of PQ. Thermogravimetric analysis indicated that the mass ratio of 4:1 was a relatively good proportion for the most production of PQ/nano-TiO2composite. Fourier transform-infrared spectrometry showed that the peak position of Ti-O-Si bond varied with the milling time. At the early stage, no characteristic peak of Ti-O-Si bond was observed, while at the later stage, new peaks at 902 cm-1and 937 cm-1appeared. Meanwhile, PQ/nano-TiO2composite-based interior paint exhibited significant DEF of 96.3% compared to that consisting of sole nanoTiO2of 92.0% under visible light illumination. As an abundant mineral resource, PQ would make interior paints with HCHO purifying effect much more efficient and cheaper.展开更多
Porous carbon spheres are prepared by direct carbonization of potassium salt of resorcinol-formaldehyde resin spheres, and are investigated as COadsorbents. It is found that the prepared carbon materials still maintai...Porous carbon spheres are prepared by direct carbonization of potassium salt of resorcinol-formaldehyde resin spheres, and are investigated as COadsorbents. It is found that the prepared carbon materials still maintain the typical spherical shapes after the activation, and have highly developed ultra-microporosity with uniform pore size, indicating that almost the activation takes place in the interior of the polymer spheres. The narrow-distributed ultra-micropores are attributed to the "in-situ homogeneous activation"effect produced by the mono-dispersed potassium ions as a form of -OK groups in the bulk of polymer spheres. The CS-1 sample prepared under a KOH/resins weight ratio of 1 shows a very high COcapture capacity of 4.83 mmol/g and good CO/Nselectivity of7-45. We believe that the presence of a welldeveloped ultra-microporosity is responsible for excellent COsorption performance at room temperature and ambient pressure.展开更多
The effects of Fe2+ on the trimethylamine N-oxide (TMAO) demethylating activity of the Harpadon nehereus kidney extract were studied in this research.The activity of the kidney extract was presumably inhibited by ethy...The effects of Fe2+ on the trimethylamine N-oxide (TMAO) demethylating activity of the Harpadon nehereus kidney extract were studied in this research.The activity of the kidney extract was presumably inhibited by ethylene diamine tetra-acetic acid (EDTA),which indicates that the kidney extract contains an enzyme or enzyme system with metal cations as activator.Activity of the kidney extract was enhanced significantly when Fe2+ was added into the model system in vitro.As the concentration of Fe2+ increased,the decomposing rate of TMAO increased rapidly until TMAO decomposed completely.The activity of the kidney extract was also enhanced by reductant such as ascorbic acid.Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) was employed to determine the content of total iron in a number of fishery products.Significant positive correlation between the contents of total iron and endogenous formaldehyde (FA) was found,especially in marine products.展开更多
The mesoporous Ti O2 has been synthesized by evaporation induced self assembly(EISA) method. The thermogravimetric/differential scanning calorimetric(TG/DSC), X-ray diffraction(XRD), high-resolution transmission elect...The mesoporous Ti O2 has been synthesized by evaporation induced self assembly(EISA) method. The thermogravimetric/differential scanning calorimetric(TG/DSC), X-ray diffraction(XRD), high-resolution transmission electron microscopy(HR-TEM) and N2 adsorption desorption and adsorption are used to study the effects of the synthesized process condition on the microstructure of the as-synthesized mesoporous Ti O2. The photocatalytic performances of as-synthesized samples are evaluated by the degradation of the formaldehyde under ultraviolet light irradiations. The results demonstrate that the as-synthesized mesoporous Ti O2 are anatase with the uniform size about 20-40 nm. The sample is prepared using cetyltrimethyl ammonium bromide(CTAB) as the template with average pore size distribution of 8.12 nm, specific surface area of 68.47 m2/g and pore volume of 0.213 m L/g. The samples show decomposition of formaldehyde 95.8% under ultraviolet light irradiations for 90 min. These results provide a basic experimental process for preparation mesoporous Ti O2, which will posses a broad prospect in terms of the applications in improving indoor air quality.展开更多
A novel photocatalytic cement based material was prepared. The distribution of TiO2 on the surface of cement was characterized by scanning electron microscope（SEM） and X-ray diffraction（XRD）, which showed the rela...A novel photocatalytic cement based material was prepared. The distribution of TiO2 on the surface of cement was characterized by scanning electron microscope（SEM） and X-ray diffraction（XRD）, which showed the relationship of photocatalysis and presence of TiO2. TiO2 also had an impact on cement hydration, which was studied by thermal analysis. With 300 W UV illuminations, formaldehyde and benzene were degraded efficiently by the prepared photocatalytic cement based materials. 15wt% TiO2/cement showed the highest degradation efficiency and capability. The results show that formaldehyde and benzene can be degraded within 4 and 9 hours, respectively. Besides, inorganic ions can induce TiO2 agglomeration. As a result, the presence of inorganic ions in cement is unfavorable for degradation. The photocatalytic cement based materials were fabricated and the degradation efficiency of formaldehyde was measured on building roof under sunlight illumination. Formaldehyde in glass chamber can be degraded thoroughly within 10 days.展开更多
Formate can be synthesized electrochemically by CO_(2) reduction reaction(CO_(2)RR)or formalde-hyde oxidation reaction(FOR).The CO_(2)RR approach suffers from kinetic-sluggish oxygen evolution reac-tion at the anode.T...Formate can be synthesized electrochemically by CO_(2) reduction reaction(CO_(2)RR)or formalde-hyde oxidation reaction(FOR).The CO_(2)RR approach suffers from kinetic-sluggish oxygen evolution reac-tion at the anode.To this end,an electrochemical sys-tem combining cathodic CO_(2)RR with anodic FOR was developed,which enables the formate electrosynthesis at ultra-low voltage.Cathodic CO_(2)RR employing the BiOCl electrode in H-cell exhibited formate Faradaic efficiency(FE)higher than 90% within a wide potential range from−0.48 to−1.32 V_(RHE).In flow cell,the current density of 100 mA cm^(−2) was achieved at−0.67 V_(RHE).The anodic FOR using the Cu_(2)O electrode displayed a low onset potential of−0.13 V_(RHE) and nearly 100%formate and H_(2) selectivity from 0.05 to 0.35 V_(RHE).The CO_(2)RR and FOR were constructed in a flow cell through membrane electrode assembly for the electrosynthesis of formate,where the CO_(2)RR//FOR delivered an enhanced current density of 100 mA cm^(−2) at 0.86 V.This work provides a promising pair-electrosynthesis of value-added chemicals with high FE and low energy consumption.展开更多
The apparent 1^st order rate constant of photodegradation of formaldehyde by carbon containing TiO2 nanoparticles has been investigated by numerical integration of mass transfer equation with measured degradation degr...The apparent 1^st order rate constant of photodegradation of formaldehyde by carbon containing TiO2 nanoparticles has been investigated by numerical integration of mass transfer equation with measured degradation degree using a tubular photoreactor. The carbon containing TiO2 nanoparticles are synthesized by the oxidation of TiCl4 in propane/air flame CVD process with futile fraction up to 0.3 and carbon mass fractions up to 0.22, respectively. Thin TiO2 film is coated on the wall of the tubular reactor by sedimentation method. Effects of rutile mass fraction and carbon content have been examined on the apparent 1 ^st order rate constant and results show that, at 570ppm of formaldehyde loaded air stream, 80% relative humidity and about 100nm thin TiOa film, the 1^st order rate constant increases with increasing rutile mass fraction up to 0.3, occurs a maximum at the carbon content of about 5% by weight and is about 2.5 times of that at carbon content about zero or above 10%.展开更多
In order to reduce the curing temperature, shorten the curing time of phenol-formaldehyde(PF) resin adhesive, and ensure the good water-solubility, NaOH and Ba(OH)_2 were used as compound catalysts. The influences of ...In order to reduce the curing temperature, shorten the curing time of phenol-formaldehyde(PF) resin adhesive, and ensure the good water-solubility, NaOH and Ba(OH)_2 were used as compound catalysts. The influences of the adding time of Ba(OH)_2, the adding amount of NaOH, Ba(OH)_2 and resorcinol on the properties of adhesives were studied. The properties of NaOH catalyzed phenol-formaldehyde(PF) adhesive, NaOH and Ba(OH)_2 compound catalyzed PF adhesive, NaOH and Ba(OH)_2 compound catalyzed phenol-resorcinol-formaldehyde(PRF) adhesive, and the prepared recombinant bamboo with three kinds of adhesives were compared. The experimental results show that NaOH and Ba(OH)_2 compound catalyst not only shortens the curing time of PF adhesive, but also guarantees the suitable water solubility of adhesive. After copolycondensation with resorcinol, the curing time of adhesive is further shortened, the water solubility is improved obviously, and the highest bonding strength is obtained. Infrared spectrum analysis shows that the reaction activity point of NaOH and Ba(OH)_2 compound catalyzed PRF adhesive will increase, so that both the curing temperature and curing enthalpy decrease.展开更多
SnO_2 nanpowder was prepared by sol-gel method.The SnO_2 based formaldehyde sensor with the doping of La_2O_3 (5wt%)-ZnO(3wt%) was fabricated.The range of the detecting concentration for formaldehyde is from 10μg/g t...SnO_2 nanpowder was prepared by sol-gel method.The SnO_2 based formaldehyde sensor with the doping of La_2O_3 (5wt%)-ZnO(3wt%) was fabricated.The range of the detecting concentration for formaldehyde is from 10μg/g to 300μg/g at 140℃.The sensitivity (S=R_0/R_g) to 10μg/g formaldehyde is 2 and to 300μg/g formaldehyde is 16.The 0.4 nm molecule-sifter layer was coated on the surface of SnO_2 material,the result shows that the selectivity of the formaldehyde sensor is improved. The La_2O_3-ZnO doped SnO_2 sensor shows better stability during 60 days testing.展开更多
Superfine Mo/ZrO_2 catalysts were prepared for partial oxidation of methane to HCHO and characterized by BET, XRD, LRS, H2-TPR and XPS. Mo existed mainly in the form of Zr(MoO4)2, and the catalytic performance and phy...Superfine Mo/ZrO_2 catalysts were prepared for partial oxidation of methane to HCHO and characterized by BET, XRD, LRS, H2-TPR and XPS. Mo existed mainly in the form of Zr(MoO4)2, and the catalytic performance and physicochemical properties of the Mo/ZrO2 catalysts were closely related to this species.展开更多
In this work, we’ve made SnO<sub>2</sub> flower formed with the aid of using easy test steps, and without cost, which is the hydrothermal approach and without a template. We have used a variety of techniq...In this work, we’ve made SnO<sub>2</sub> flower formed with the aid of using easy test steps, and without cost, which is the hydrothermal approach and without a template. We have used a variety of techniques to characterize SnO<sub>2</sub> flower-shaped by (SEM, TEM, XRD, BET and XPS) instruments. Confirmatory tests carried out have proven that the surface of the tetragonal structure of SnO<sub>2</sub> has a rough surface which makes it excellent for its gas-sensing properties. The gas detection test of SnO<sub>2</sub> flower-shaped proved that it possesses the selectivity of formaldehyde gas (about 30), the optimum operating temperature of the sensor is 220<span style="white-space:nowrap;"><span style="white-space:nowrap;">°</span></span>C, and also the sensor has a high response time and recovery time is (5 s and 22 s) to 100 ppm, respectively. Particularly, the sensor has an obvious response value (2) when exposed to 5 ppm formaldehyde. As well, the mechanism of gas-sensing was also discussed.展开更多
We have investigated the photoinduced decomposition of formaldehyde （CH2O） on a rutile TiO2（100）-（1×1） surface at 355 nrn using ternperature-prograrnrned desorption. Products, formate （HCOO）, methyl radic...We have investigated the photoinduced decomposition of formaldehyde （CH2O） on a rutile TiO2（100）-（1×1） surface at 355 nrn using ternperature-prograrnrned desorption. Products, formate （HCOO）, methyl radical （CH3.）, ethylene （C2H4）, and methanol （CH3OH） have been detected. The initial step in the decomposition of CH2O on the futile TiO2（100）-（1×1） surface is the formation of a dioxyrnethylene intermediate in which the carbonyl O atom of CH2O is bound to a Ti atom at the five-fold-coordinated Ti4＋ （Tisc） site and its carbonyl C atom bound to a nearby bridge-bonded oxygen （Oh） atom, respectively. During 355 nrn irradiation, the dioxymethylene intermediate can transfer an H atom to the Ob atom, thus forming HCOO directly, which is considered as the main reaction channel. In addition, the dioxyrnethylene intermediate can also transfer methylene to the Ob row and break the C-O bond, thus leaving the original carbonyl O atom at the Tisc site. After the transfer of methylene, several pathways to products are available. Thus, we have found that Ob atoms are intimately involved in the photoinduced decomposition of CH2O on the futile TiO2 （100）-（1× 1） surface.展开更多
文摘Oxygen vacancy （Ov） has significant influence on physical and chemical properties of TiO2 systems, especially on surface catalytic processes. In this work, we investigate the effects of Ov on the adsorption of formaldehyde （HCHO） on TiO2（110） surfaces through first- principles calculations. With the existence of Ov, we find the spatial distribution of surface excess charge can change the relative stability of various adsorption configurations. In this case, the bidentate adsorption at five-coordinated Ti （Tisc） can be less stable than the monodentate adsorption. And HCHO adsorbed in Ov becomes the most stable structure. These results are in good agreement with experimental observations, which reconcile the long-standing deviation between the theoretical prediction and experimental results. This work brings insights into how the excess charge affects the molecule adsorption on metal oxide surface.
基金The National Natural Science Foundation of China(No. 40275038)
文摘Catalytic elimination of formaldehyde(HCHO) was investigated over Cu-Al_2O_3 catalyst at room temperature. The results indicated that no oxidation of HCHO into CO_2 occurs at room temperature, but the adsorption of HCHO occurs on the catalyst surface. With the increase of gas hourly space velocity(GHSV) and inlet HCHO concentration, the time to reach saturation was shortened proportionally. The results of the in situ DRIFTS, Density functional theory calculations and temperature programmed desorption(TPD) showed that HCHO was completely oxidized into HCOOH over Cu-Al_2O_3 at room temperature. With increasing the temperature in a flow of helium, HCOOH was completely decomposed into CO_2 over the catalyst surface, and the deactivated Cu-Al_2O_3 is regenerated at the same time. In addition, although Cu had no obvious influence on the adsorption of HCHO on Al_2O_3, Cu dramatically lowered the decomposition temperature of HCOOH into CO_2. It was shown that Cu-Al_2O_3 catalyst had a good ability for the removal of HCHO, and appeared to be promising for its application in destroying HCHO at room temperature.
基金Project supported by the Science Project of Harbin City(No. H2001-12)the Youth Foundation of School of Municipal and Environmental Engineering in Harbin Institute of Technology(No. 01306914).
文摘The degradation of formaldehyde gas was studied using UV/TiO2/O3 process under the condition of continuous flow mode. The effects of humidity, initial formaldehyde concentration, residence time and ozone adding amount on degradation of formaldehyde gas were investigated. The experimental results indicated that the combination of ozonation with photocatalytic oxidation on the degradation of formaldehyde showed a synergetic action, e.g,, it could considerably increase decomposing of formaldehyde. The degradation efficiency of formaldehyde was between 73.6% and 79.4% while the initial concentration in the range of 1.84--24 mg/m^3 by O3/TiO2flJV process. The optimal humidity was about 50% in UV/TiO2/O3 processs and degradation of formaldehyde increases from 39.0% to 94.1% when the ozone content increased from 0 to 141 mg/m^3. Furthermore, the kinetics of formaldehyde degradation reaction could be described by Langmuir-Hinshelwood model. The rate constant k of 46.72 mg/（m^3.min） and Langmuir adsorption coefficient K of 0.0268 m^3/mg were obtained.
基金Funded by the National Natural Science Foundation of China(No.41130746)
文摘Powder quartz(PQ)/nano-TiO2composite was prepared by a mechanochemical method. Based on as-prepared PQ/nano-TiO2composite, we prepared interior paints and investigated the degradation efficiency of formaldehyde(DEF). Scanning electron microscopy showed that nano-TiO2got well dispersed by the adding of PQ. Thermogravimetric analysis indicated that the mass ratio of 4:1 was a relatively good proportion for the most production of PQ/nano-TiO2composite. Fourier transform-infrared spectrometry showed that the peak position of Ti-O-Si bond varied with the milling time. At the early stage, no characteristic peak of Ti-O-Si bond was observed, while at the later stage, new peaks at 902 cm-1and 937 cm-1appeared. Meanwhile, PQ/nano-TiO2composite-based interior paint exhibited significant DEF of 96.3% compared to that consisting of sole nanoTiO2of 92.0% under visible light illumination. As an abundant mineral resource, PQ would make interior paints with HCHO purifying effect much more efficient and cheaper.
基金the financial supports by the Natural Science Foundation of China (NSFC21576158, 21476132, 21576159 and 21403130)Shandong Provincial Natural Science Foundation, China (No. 2015 ZRB01765)
文摘Porous carbon spheres are prepared by direct carbonization of potassium salt of resorcinol-formaldehyde resin spheres, and are investigated as COadsorbents. It is found that the prepared carbon materials still maintain the typical spherical shapes after the activation, and have highly developed ultra-microporosity with uniform pore size, indicating that almost the activation takes place in the interior of the polymer spheres. The narrow-distributed ultra-micropores are attributed to the "in-situ homogeneous activation"effect produced by the mono-dispersed potassium ions as a form of -OK groups in the bulk of polymer spheres. The CS-1 sample prepared under a KOH/resins weight ratio of 1 shows a very high COcapture capacity of 4.83 mmol/g and good CO/Nselectivity of7-45. We believe that the presence of a welldeveloped ultra-microporosity is responsible for excellent COsorption performance at room temperature and ambient pressure.
基金supported by the National Natural Science Foundation of China (No.30871949)
文摘The effects of Fe2+ on the trimethylamine N-oxide (TMAO) demethylating activity of the Harpadon nehereus kidney extract were studied in this research.The activity of the kidney extract was presumably inhibited by ethylene diamine tetra-acetic acid (EDTA),which indicates that the kidney extract contains an enzyme or enzyme system with metal cations as activator.Activity of the kidney extract was enhanced significantly when Fe2+ was added into the model system in vitro.As the concentration of Fe2+ increased,the decomposing rate of TMAO increased rapidly until TMAO decomposed completely.The activity of the kidney extract was also enhanced by reductant such as ascorbic acid.Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) was employed to determine the content of total iron in a number of fishery products.Significant positive correlation between the contents of total iron and endogenous formaldehyde (FA) was found,especially in marine products.
基金Projects(51102026,51272032) supported by the Program for the National Natural Science Foundation of ChinaProject(11A014) supported by the Scientific Research Fund of Hunan Provincial Education DepartmentProject supported by the Aid Program for Science and Technology Innovative Research Team in Higher Educational Instituions of Hunan Province,China
文摘The mesoporous Ti O2 has been synthesized by evaporation induced self assembly(EISA) method. The thermogravimetric/differential scanning calorimetric(TG/DSC), X-ray diffraction(XRD), high-resolution transmission electron microscopy(HR-TEM) and N2 adsorption desorption and adsorption are used to study the effects of the synthesized process condition on the microstructure of the as-synthesized mesoporous Ti O2. The photocatalytic performances of as-synthesized samples are evaluated by the degradation of the formaldehyde under ultraviolet light irradiations. The results demonstrate that the as-synthesized mesoporous Ti O2 are anatase with the uniform size about 20-40 nm. The sample is prepared using cetyltrimethyl ammonium bromide(CTAB) as the template with average pore size distribution of 8.12 nm, specific surface area of 68.47 m2/g and pore volume of 0.213 m L/g. The samples show decomposition of formaldehyde 95.8% under ultraviolet light irradiations for 90 min. These results provide a basic experimental process for preparation mesoporous Ti O2, which will posses a broad prospect in terms of the applications in improving indoor air quality.
基金Funded by the National Natural Science Foundation of China(Nos.51478370 and 51461135005)
文摘A novel photocatalytic cement based material was prepared. The distribution of TiO2 on the surface of cement was characterized by scanning electron microscope（SEM） and X-ray diffraction（XRD）, which showed the relationship of photocatalysis and presence of TiO2. TiO2 also had an impact on cement hydration, which was studied by thermal analysis. With 300 W UV illuminations, formaldehyde and benzene were degraded efficiently by the prepared photocatalytic cement based materials. 15wt% TiO2/cement showed the highest degradation efficiency and capability. The results show that formaldehyde and benzene can be degraded within 4 and 9 hours, respectively. Besides, inorganic ions can induce TiO2 agglomeration. As a result, the presence of inorganic ions in cement is unfavorable for degradation. The photocatalytic cement based materials were fabricated and the degradation efficiency of formaldehyde was measured on building roof under sunlight illumination. Formaldehyde in glass chamber can be degraded thoroughly within 10 days.
基金This work was supported by the National Key R&D Program of China(2020YFA0710000)the National Natural Science Foundation of China(22122901,21902047)+1 种基金the Provincial Natural Science Foundation of Hunan(2020JJ5045,2021JJ20024,2021RC3054)the Shenzhen Science and Technology Program(JCYJ20210324140610028).
文摘Formate can be synthesized electrochemically by CO_(2) reduction reaction(CO_(2)RR)or formalde-hyde oxidation reaction(FOR).The CO_(2)RR approach suffers from kinetic-sluggish oxygen evolution reac-tion at the anode.To this end,an electrochemical sys-tem combining cathodic CO_(2)RR with anodic FOR was developed,which enables the formate electrosynthesis at ultra-low voltage.Cathodic CO_(2)RR employing the BiOCl electrode in H-cell exhibited formate Faradaic efficiency(FE)higher than 90% within a wide potential range from−0.48 to−1.32 V_(RHE).In flow cell,the current density of 100 mA cm^(−2) was achieved at−0.67 V_(RHE).The anodic FOR using the Cu_(2)O electrode displayed a low onset potential of−0.13 V_(RHE) and nearly 100%formate and H_(2) selectivity from 0.05 to 0.35 V_(RHE).The CO_(2)RR and FOR were constructed in a flow cell through membrane electrode assembly for the electrosynthesis of formate,where the CO_(2)RR//FOR delivered an enhanced current density of 100 mA cm^(−2) at 0.86 V.This work provides a promising pair-electrosynthesis of value-added chemicals with high FE and low energy consumption.
文摘The apparent 1^st order rate constant of photodegradation of formaldehyde by carbon containing TiO2 nanoparticles has been investigated by numerical integration of mass transfer equation with measured degradation degree using a tubular photoreactor. The carbon containing TiO2 nanoparticles are synthesized by the oxidation of TiCl4 in propane/air flame CVD process with futile fraction up to 0.3 and carbon mass fractions up to 0.22, respectively. Thin TiO2 film is coated on the wall of the tubular reactor by sedimentation method. Effects of rutile mass fraction and carbon content have been examined on the apparent 1 ^st order rate constant and results show that, at 570ppm of formaldehyde loaded air stream, 80% relative humidity and about 100nm thin TiOa film, the 1^st order rate constant increases with increasing rutile mass fraction up to 0.3, occurs a maximum at the carbon content of about 5% by weight and is about 2.5 times of that at carbon content about zero or above 10%.
基金Funded by the China Postdoctoral Science Foundation Funded Project(2015M572276)the Natural Science Foundation of Hunan Province,China(2016JJ3184)the Hunan Major Science and Technology Projects(2011FJ1006)
文摘In order to reduce the curing temperature, shorten the curing time of phenol-formaldehyde(PF) resin adhesive, and ensure the good water-solubility, NaOH and Ba(OH)_2 were used as compound catalysts. The influences of the adding time of Ba(OH)_2, the adding amount of NaOH, Ba(OH)_2 and resorcinol on the properties of adhesives were studied. The properties of NaOH catalyzed phenol-formaldehyde(PF) adhesive, NaOH and Ba(OH)_2 compound catalyzed PF adhesive, NaOH and Ba(OH)_2 compound catalyzed phenol-resorcinol-formaldehyde(PRF) adhesive, and the prepared recombinant bamboo with three kinds of adhesives were compared. The experimental results show that NaOH and Ba(OH)_2 compound catalyst not only shortens the curing time of PF adhesive, but also guarantees the suitable water solubility of adhesive. After copolycondensation with resorcinol, the curing time of adhesive is further shortened, the water solubility is improved obviously, and the highest bonding strength is obtained. Infrared spectrum analysis shows that the reaction activity point of NaOH and Ba(OH)_2 compound catalyzed PRF adhesive will increase, so that both the curing temperature and curing enthalpy decrease.
文摘SnO_2 nanpowder was prepared by sol-gel method.The SnO_2 based formaldehyde sensor with the doping of La_2O_3 (5wt%)-ZnO(3wt%) was fabricated.The range of the detecting concentration for formaldehyde is from 10μg/g to 300μg/g at 140℃.The sensitivity (S=R_0/R_g) to 10μg/g formaldehyde is 2 and to 300μg/g formaldehyde is 16.The 0.4 nm molecule-sifter layer was coated on the surface of SnO_2 material,the result shows that the selectivity of the formaldehyde sensor is improved. The La_2O_3-ZnO doped SnO_2 sensor shows better stability during 60 days testing.
基金This work is supported by the Ministry of Science and Technology(G199902240-06)
文摘Superfine Mo/ZrO_2 catalysts were prepared for partial oxidation of methane to HCHO and characterized by BET, XRD, LRS, H2-TPR and XPS. Mo existed mainly in the form of Zr(MoO4)2, and the catalytic performance and physicochemical properties of the Mo/ZrO2 catalysts were closely related to this species.
文摘In this work, we’ve made SnO<sub>2</sub> flower formed with the aid of using easy test steps, and without cost, which is the hydrothermal approach and without a template. We have used a variety of techniques to characterize SnO<sub>2</sub> flower-shaped by (SEM, TEM, XRD, BET and XPS) instruments. Confirmatory tests carried out have proven that the surface of the tetragonal structure of SnO<sub>2</sub> has a rough surface which makes it excellent for its gas-sensing properties. The gas detection test of SnO<sub>2</sub> flower-shaped proved that it possesses the selectivity of formaldehyde gas (about 30), the optimum operating temperature of the sensor is 220<span style="white-space:nowrap;"><span style="white-space:nowrap;">°</span></span>C, and also the sensor has a high response time and recovery time is (5 s and 22 s) to 100 ppm, respectively. Particularly, the sensor has an obvious response value (2) when exposed to 5 ppm formaldehyde. As well, the mechanism of gas-sensing was also discussed.
基金supported by the National Natural Science Foundation of China(No.21673235 and No.21403224)the Youth Innovation Promotion Association CAS,and the Key Research Program of the Chinese Academy of Sciences
文摘We have investigated the photoinduced decomposition of formaldehyde （CH2O） on a rutile TiO2（100）-（1×1） surface at 355 nrn using ternperature-prograrnrned desorption. Products, formate （HCOO）, methyl radical （CH3.）, ethylene （C2H4）, and methanol （CH3OH） have been detected. The initial step in the decomposition of CH2O on the futile TiO2（100）-（1×1） surface is the formation of a dioxyrnethylene intermediate in which the carbonyl O atom of CH2O is bound to a Ti atom at the five-fold-coordinated Ti4＋ （Tisc） site and its carbonyl C atom bound to a nearby bridge-bonded oxygen （Oh） atom, respectively. During 355 nrn irradiation, the dioxymethylene intermediate can transfer an H atom to the Ob atom, thus forming HCOO directly, which is considered as the main reaction channel. In addition, the dioxyrnethylene intermediate can also transfer methylene to the Ob row and break the C-O bond, thus leaving the original carbonyl O atom at the Tisc site. After the transfer of methylene, several pathways to products are available. Thus, we have found that Ob atoms are intimately involved in the photoinduced decomposition of CH2O on the futile TiO2 （100）-（1× 1） surface.
