Co-reporter:Ying Luo;Jiawei Xue;Xiaodi Zhu;Jose Daniel;Xiang Gao;Song Sun;Chen Gao
RSC Advances (2011-Present) 2017 vol. 7(Issue 10) pp:5821-5826
Publication Date(Web):2017/01/16
DOI:10.1039/C6RA26072A
A series of Mo-doped Ca2NiWO6 (Ca2NiW1−xMoxO6, x = 0–0.05) samples were synthesized by a solid-state reaction. The physical and optical properties of these photocatalysts were characterized by X-ray diffraction, X-ray absorption fine structure, UV-visible diffuse reflectance spectra, and the band structure along with density of states were calculated by the plane-wave-based density functional theory. The photocatalytic activity of oxygen evolution from water was evaluated under visible light irradiation. The Mo doping significantly increased the photocatalytic activity of Ca2NiWO6. The optimal Ca2NiW0.97Mo0.03O6 showed an oxygen evolution rate approximately 2 times higher than that of the pure Ca2NiWO6. The characterization results indicated that the Mo-doped Ca2NiWO6 maintained the double perovskite structure. The Mo6+ ions were substituted into the W6+ sites in the lattice, causing a certain amount of lattice distortion and promoting the formation of oxygen vacancies. Furthermore, the Mo doping introduced impurity energy levels into the band structure of Ca2NiWO6. Consequently, the conduction band changed from discrete to continuous and the bottom of the conduction band was shifted to more positive potential, compared to that of pure Ca2NiWO6, leading to a lower band gap and higher absorbance in the wider visible light region. These characteristics are responsible for the high photocatalytic activity of the oxygen evolution reaction.
Co-reporter:Wei Xie, Jilong Zhou, Lili Ji, Song Sun, Haibin Pan, Junfa Zhu, Chen Gao and Jun Bao
RSC Advances 2016 vol. 6(Issue 45) pp:38741-38745
Publication Date(Web):01 Apr 2016
DOI:10.1039/C6RA05332G
Improving the C2+ alcohols selectivity is the most difficult challenge in higher alcohol synthesis (HAS) from syngas. Herein, three effective strategies were combined to develop a Mo-based catalyst for HAS. The sol–gel method produced a highly homogeneous distribution of components, which ensured intimate and sufficient contact between different active sites. The incorporation of Mn oxide enhanced the interaction between Co and Mo and thus promoted the growth of the alcohol chain. More importantly, the reduction degrees of Co and Mo can be tuned precisely. The prepared Mn/K/Co/Mo catalysts show unusual activity for HAS.
Co-reporter:Jiawei Xue;Xiaodi Zhu;Dr. Yi Zhang;Dr. Wendong Wang;Wei Xie;Jilong Zhou;Dr. Jun Bao;Ying Luo;Xiang Gao;Dr. Yong Wang;Dr. Ling-yun Jang;Dr. Song Sun;Dr. Chen Gao
ChemCatChem 2016 Volume 8( Issue 12) pp:2010-2014
Publication Date(Web):
DOI:10.1002/cctc.201600237
Abstract
The involvement of oxygen vacancies in the electronic and structural properties and photocatalytic activity of hydrogenated TiO2 (H-TiO2) for water splitting are currently under debate. Herein, the process for the formation of oxygen vacancies in H-TiO2 is illustrated for the first time to verify the role of these vacancies on the surface and in the bulk of H-TiO2 by using surface-sensitive soft X-ray techniques and bulk-information-included hard X-ray techniques for the O K-edges and Ti K-edges, respectively. We find that oxygen vacancies on the surface and in the bulk contribute differently to tailing of the conduction band of H-TiO2. By controlling the degree of hydrogenation to restrict tailing of the conduction band to just above the H+/H2 redox potential, the most favorable disordered structure for photocatalytic H2 evolution is developed. This work promotes a better understanding of the possible negative consequence of hydrogenated semiconductors in H2 evolution apart from the positive effect on visible-light response.
Co-reporter:Jiawei Xue;Xiaodi Zhu;Dr. Yi Zhang;Dr. Wendong Wang;Wei Xie;Jilong Zhou;Dr. Jun Bao;Ying Luo;Xiang Gao;Dr. Yong Wang;Dr. Ling-yun Jang;Dr. Song Sun;Dr. Chen Gao
ChemCatChem 2016 Volume 8( Issue 12) pp:
Publication Date(Web):
DOI:10.1002/cctc.201600628
Abstract
The front cover artwork for Issue 12/2016 is provided by researchers from the University of Science & Technology of China. The image shows that hydrogenated TiO2 with an appropriate hydrogenation time exhibits much higher photocatalytic H2 evolution activity than that with an excessive hydrogenation degree. See the Communication itself at http://dx.doi.org/10.1002/cctc.201600237.
Co-reporter:Jiawei Xue;Xiaodi Zhu;Dr. Yi Zhang;Dr. Wendong Wang;Wei Xie;Jilong Zhou;Dr. Jun Bao;Ying Luo;Xiang Gao;Dr. Yong Wang;Dr. Ling-yun Jang;Dr. Song Sun;Dr. Chen Gao
ChemCatChem 2016 Volume 8( Issue 12) pp:
Publication Date(Web):
DOI:10.1002/cctc.201600682
Co-reporter:Meimei Lv, Wei Xie, Song Sun, Gaimei Wu, Lirong Zheng, Shengqi Chu, Chen Gao and Jun Bao
Catalysis Science & Technology 2015 vol. 5(Issue 5) pp:2925-2934
Publication Date(Web):23 Mar 2015
DOI:10.1039/C5CY00083A
A series of activated-carbon-supported K–Co–Mo catalysts (K–Co–Mo/AC) were prepared by using a sol–gel method combined with incipient wetness impregnation. The catalyst structure was characterized by X-ray diffraction (XRD), N2 adsorption–desorption, X-ray absorption fine structure spectroscopy and X-ray photoelectron spectroscopy, and their catalytic performance toward synthesis of higher alcohols from syngas was investigated. The large surface area and pore volume of the support facilitated the distribution of metal particles and high dispersion of metals. At low Mo loading, the Mo atoms on the activated carbon surface were mainly tetrahedrally coordinated Mo6+ species. With an increase in the Mo loading, the coordination environment of the surface Mo atoms gradually transformed from tetrahedrally coordinated Mo6+ to octahedrally coordinated Mo4+, indicating that an increase in the Mo loading promoted the reduction of Mo6+ species to Mo4+ species. After reduction, it was observed that a type of a lower state Moδ+ (1 < δ < 4) species was present on the surface, which is suggested to be responsible for alcohol synthesis. Compared to the unsupported catalyst, K–Co–Mo/AC exhibited a significantly higher activity for alcohol formation. In particular, the C2+ alcohol content increased significantly. This can be attributed to the fact that the supported catalysts have a high active surface area, and the mesoporous structure is suggested to prolong the residence time of intermediates to form alcohols in the pores to some extent, thus promoting the formation of higher alcohols. Under the conditions of a Mo/AC weight ratio of 40% and a reduction temperature of 798 K, the K–Co–Mo/AC catalyst exhibited the highest activity for alcohol formation, which may be attributed to the high content of Moδ+ (1 < δ < 4) species on the surface.
Co-reporter:Jianjun Ding, Wenhao Yan, Song Sun, Jun Bao, and Chen Gao
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 15) pp:12877
Publication Date(Web):July 7, 2014
DOI:10.1021/am5028296
A series of CaIn2S4-reduced graphene oxide (RGO) nanocomposites with different RGO contents were fabricated using a facile hydrothermal approach. During the hydrothermal process, the reduction of graphene oxide to RGO, in situ deposition of synthesized CaIn2S4 nanoparticles on RGO nanosheets and formation of chemical-bonding CaIn2S4-RGO nanocomposites were performed simultaneously. Under visible light irradiation, the as-prepared CaIn2S4-RGO nanocomposites showed enhanced photocatalytic performance for rhodamine B degradation and phenol oxidation. The sample with 5 wt % RGO hybridized CaIn2S4 exhibited the highest photocatalytic activity. The enhancement of photocatalytic performance may be related to the increased adsorption/reaction sites, positive shift of the valence band potential, and high separation efficiency of photogenerated charge carriers due to the electronic interaction between CaIn2S4 and RGO. We hope that this work can not only provide an in-depth study on the photocatalytic mechanism of RGO-enhanced activity, but also provide some insights for fabricating efficient and stable RGO-based photocatalysts in the potential applications of purifying polluted water resources.Keywords: CaIn2S4; hydrothermal; nanocomposites; reduced graphene oxide; visible-light photocatalysis
Co-reporter:Jianjun Ding ; Bin Hong ; Zhenlin Luo ; Song Sun ; Jun Bao ;Chen Gao
The Journal of Physical Chemistry C 2014 Volume 118(Issue 48) pp:27690-27697
Publication Date(Web):November 12, 2014
DOI:10.1021/jp508497a
A novel ternary sulfide photocatalyst of monoclinic CaIn2S4 with excellent photocatalytic H2 evolution activity is synthesized via a high-temperature sulfurization approach. The precursor orthorhombic CaIn2O4 can be converted in situ to monoclinic CaIn2S4 by using H2S gas as the sulfurization reagent once the sulfurization temperature exceeds 773 K. The obtained yellow powders have a mesoporous structure and a chain-shape morphology with large surface area and high pore volume. SEM and TEM observations indicate that specific nanostep structures are formed on the surface of monoclinic CaIn2S4. Under visible light irradiation, monoclinic CaIn2S4 exhibits considerable performance for photocatalytic hydrogen production. A high H2 evolution rate of 30.2 μmol/h with good stability is achieved from Na2S/Na2SO3 aqueous solution with the deposition of 0.5 wt % Pt nanoparticles, 30 times higher than that of cubic CaIn2S4, which makes it a new promising candidate photocatalyst for hydrogen production. This work can provide an effective approach to the fabrication of other mesoporous sulfide photocatalysts with high performance.
Co-reporter:Manman Zhang, Wei Zhang, Wei Xie, Zeming Qi, Gaimei Wu, Meimei Lv, Song Sun, Jun Bao
Journal of Molecular Catalysis A: Chemical 2014 Volume 395() pp:269-275
Publication Date(Web):December 2014
DOI:10.1016/j.molcata.2014.08.029
•The addition of cobalt promoted the reduction of Mo species to Moδ+ species.•The addition of cobalt promoted the syngas adsorption on Moδ+ species.•The Moδ+ species is suggested to be responsible for the mixed alcohol synthesis.The K–Co–Mo/C catalysts with different molar ratios of Co/Mo and reduction temperatures were prepared by a sol–gel method and characterized by the means of XRD, H2-TPR, XPS and in situ DRIFTS. The addition of moderate amount of cobalt can promote the reduction of Mo species to Moδ+ species. With increasing the Co content, the CO adsorption strength on Moδ+ species increased and was up to the maximum when Co/Mo = 0.5. Further increasing the Co content led to the decrease of surface Moδ+ species because that the formation of CoMoO3 inhibited the further reduction of Mo4+ species. Increasing the reduction temperature resulted in the decrease of the surface cobalt content significantly. The CO adsorption strength on Moδ+ species reached a maximum at 773 K. Higher reduction temperature caused the decrease of CO adsorption strength because of the sintering of catalyst. It suggested that the surface Moδ+ species is responsible for the alcohol synthesis. The high activity of the K–Co–Mo/C catalysts with Co/Mo ratio of 0.5 for alcohol synthesis should be attributed to its high Moδ+ content on the surface.The addition of moderate amount of cobalt promoted the reduction of Mo species to Moδ+ species. The adsorption strength of CO on the Moδ+ site reached a maximum on the catalyst with Co/Mo ratio of 0.5 and reduction temperature at 773 K. The results were consistent with the catalytic activity of the catalysts.
Co-reporter:Dr. Song Sun;Fan Zhang;Dr. Zeming Qi;Dr. Jianjun Ding;Dr. Jun Bao; Chen Gao
ChemCatChem 2014 Volume 6( Issue 9) pp:2535-2539
Publication Date(Web):
DOI:10.1002/cctc.201402332
Abstract
Despite several decades of intensive studies, only a few commercial photocatalysts have been discovered by means of the conventional one-at-a-time synthesis and characterization. Herein, a high-throughput screening of photocatalysts for air purification using an infrared microscope, equipped with a set of homemade in situ gas reaction cells and a gas dosing system, is described. 1.0 % La3+/0.4 % Nd3+-TiO2 was rapidly selected as an active photocatalyst for toluene degradation with a mineralization rate of 93.4 % at a humidity level of 70 % in 2 h. The excellent agreement between our combinatorial results and those of the bulk samples confirms the reliability of the developed rapid screening method. In addition, the investigation of the effects of pretreatment with NH3 and H2S on the photocatalytic activity also offers some information about the surface modification for air purification.
Co-reporter:Song Sun, Jianjun Ding, Jun Bao, Chen Gao, Zeming Qi, Xiaoyan Yang, Bo He, Chengxiang Li
Applied Surface Science 2012 Volume 258(Issue 12) pp:5031-5037
Publication Date(Web):1 April 2012
DOI:10.1016/j.apsusc.2012.01.075
Abstract
The Fe-TiO2 photocatalysts synthesized by a sol–gel method have the mesoporous structure with a narrow pore size distribution, large pore volume and high surface area. The incorporated Fe3+ substitutes the octahedrally coordinated Ti4+ in the TiO2 lattice to extend the absorption of TiO2 to visible light region and promote the formation of electron–hole pair. Additionally, the separation and transportation efficiency increase with the doping of Fe3+ increasing from 0.1% to 0.7%, while decreases remarkably with the doping concentration increasing from 0.7% to 1.5%. The Fe-TiO2 shows excellent photocatalytic performance for toluene degradation under visible light irradiation. The optimal Fe/Ti ratio is 0.7%. Partial deactivation of the photocatalytic activity was observed after 20 consecutive reaction runs. From the in situ DRIFTS experiment, the deactivation reason can be attributed to the formation of stable intermediates, such as benzaldehyde and benzoic acid, which occupied the active sites on the surface of the photocatalyst. The adsorbed benzaldehyde and benzoic acid can be removed with heat treatment at 653 K for 3 h and the deactivated photocatalyst can be regenerated completely.
Co-reporter:Song Sun, Xiaoyan Yang, Yi Zhang, Fan Zhang, Jianjun Ding, Jun Bao, Chen Gao
Progress in Natural Science: Materials International 2012 Volume 22(Issue 6) pp:639-643
Publication Date(Web):December 2012
DOI:10.1016/j.pnsc.2012.11.008
A kind of cubic ZnFe2O4 with spinel structure was synthesized by an improved solution combustion method via a facile and environmentally friendly pathway and their photocatalytic activity under visible light radiation was investigated. The particle synthesized under the ignition temperature of 573 K has a pure phase. While a small amount impurities, α-Fe2O3 and ZnO, were formed in the sample during the combustion process at higher ignition temperature of 623 K. The synthesized ZnFe2O4 has a sponge-like porous structure and wide absorption in the visible-light region. The impurities α-Fe2O3 and ZnO formed in the sample probably enhance the reduction and oxidation ability and promote the separation of photo-generated electrons and holes. Comparing with ZnFe2O4 synthesized by the conventional solid state reaction, the ZnFe2O4 derived by solution combustion method showed the better photocatalytic activity under visible light radiation.
Co-reporter:Song Sun;Jianjun Ding;Chen Gao;Zeming Qi;Chengxiang Li
Catalysis Letters 2010 Volume 137( Issue 3-4) pp:239-246
Publication Date(Web):2010 July
DOI:10.1007/s10562-010-0358-4
The adsorption and photocatalytic oxidation of formaldehyde on the pure TiO2 under dry and humid conditions were studied by in situ diffuse reflectance Fourier transform infrared spectroscopy. It was found that the formaldehyde molecules can be adsorbed on the hydroxyl groups on the TiO2 surface via hydrogen bonding. With UV irradiation, the adsorbed formaldehyde rapidly converts to the formate species even on the pure TiO2 at room temperature and atmospheric pressure. In the dry environment, the superoxide radical anion O2−•, formed by adsorbed oxygen reacting with electrons, is suggested to play an important role in the formaldehyde oxidation. The introduction of water vapor provides a large amount of water and hydroxyl groups on the catalyst surface. Oxidation of water and hydroxyl groups by the photogenerated holes produces very active OH• radicals, which take part in the redox reactions and improve significantly the mineralization rate of formaldehyde on the TiO2 due to its high redox potential.Open image in new window
Co-reporter:Jun Bao, YiLu Fu, ZhongHai Sun and Chen Gao
Chemical Communications 2003 (Issue 6) pp:746-747
Publication Date(Web):25 Feb 2003
DOI:10.1039/B212504H
A highly homogeneous and dispersed K-Co-Mo/C catalyst which prepared by a sol–gel method exhibits high alcohol yield, especially high C2+OH selectivity for mixed alcohol synthesis from CO + H2.
Co-reporter:Xiaodi Zhu, Fan Zhang, Mengjiao Wang, Xiang Gao, Ying Luo, Jiawei Xue, Yi Zhang, Jianjun Ding, Song Sun, Jun Bao, Chen Gao
Applied Catalysis A: General (5 July 2016) Volume 521() pp:42-49
Publication Date(Web):5 July 2016
DOI:10.1016/j.apcata.2015.10.017
Co-reporter:Xiaodi Zhu, Fan Zhang, Mengjiao Wang, Xiang Gao, Ying Luo, Jiawei Xue, Yi Zhang, Jianjun Ding, Song Sun, Jun Bao, Chen Gao
Applied Catalysis A: General (5 August 2016) Volume 523() pp:
Publication Date(Web):5 August 2016
DOI:10.1016/j.apcata.2016.06.010
Co-reporter:Meimei Lv, Wei Xie, Song Sun, Gaimei Wu, Lirong Zheng, Shengqi Chu, Chen Gao and Jun Bao
Catalysis Science & Technology (2011-Present) 2015 - vol. 5(Issue 5) pp:NaN2934-2934
Publication Date(Web):2015/03/23
DOI:10.1039/C5CY00083A
A series of activated-carbon-supported K–Co–Mo catalysts (K–Co–Mo/AC) were prepared by using a sol–gel method combined with incipient wetness impregnation. The catalyst structure was characterized by X-ray diffraction (XRD), N2 adsorption–desorption, X-ray absorption fine structure spectroscopy and X-ray photoelectron spectroscopy, and their catalytic performance toward synthesis of higher alcohols from syngas was investigated. The large surface area and pore volume of the support facilitated the distribution of metal particles and high dispersion of metals. At low Mo loading, the Mo atoms on the activated carbon surface were mainly tetrahedrally coordinated Mo6+ species. With an increase in the Mo loading, the coordination environment of the surface Mo atoms gradually transformed from tetrahedrally coordinated Mo6+ to octahedrally coordinated Mo4+, indicating that an increase in the Mo loading promoted the reduction of Mo6+ species to Mo4+ species. After reduction, it was observed that a type of a lower state Moδ+ (1 < δ < 4) species was present on the surface, which is suggested to be responsible for alcohol synthesis. Compared to the unsupported catalyst, K–Co–Mo/AC exhibited a significantly higher activity for alcohol formation. In particular, the C2+ alcohol content increased significantly. This can be attributed to the fact that the supported catalysts have a high active surface area, and the mesoporous structure is suggested to prolong the residence time of intermediates to form alcohols in the pores to some extent, thus promoting the formation of higher alcohols. Under the conditions of a Mo/AC weight ratio of 40% and a reduction temperature of 798 K, the K–Co–Mo/AC catalyst exhibited the highest activity for alcohol formation, which may be attributed to the high content of Moδ+ (1 < δ < 4) species on the surface.
