线团状C/BiOCl复合材料的合成及其光催化性能研究

以蔗糖作为表面活性剂,采用水热法成功制备出可见光响应的线团状C/BiOCl复合光催化剂。对所制备样品进行一系列表征。结果表明:所制备样品显著吸收可见光;添加0.3 g蔗糖制备的样品呈线团状分级结构,且具有最好的可见光催化活性,200 min RhB降解率约为50%。自由基抑制实验发现:光催化降解RhB过程中主要的活性物种为·OH和·O^(2-)。循环实验发现样品具有良好的循环稳定性。

微球状BiOCl/C-TiO_(2)复合材料的制备及光催化性能

通过溶剂热法制备了球状C-TiO_(2)催化剂以及BiOCl/C-TiO_(2)复合光催化材料。与纯TiO_(2)相比,球状C-TiO_(2)和BiOCl/C-TiO_(2)的禁带宽度显著降低。以亚甲基蓝为降解目标,当染料质量浓度为25 mg/L、pH为7时,0.1 g BiOCl/CTiO_(2)对其的降解率在1 h可达到81.44%,催化效率达64.15%,其动力学过程符合一级动力学模型。

Electronic Structure and Optical-absorption Properties of C-, N-, and S-doped BiOCl: the First-principles Calculations

Impurity formation energy, electronic structure, and photocatalytic properties of C-, N-, or S-doped BiOCl are investigated by density-functional theory plus U calculations(DFT + U). Results show that the doping effect of S is better than that of C or N on the tunable photocatalytic activities of BiOCl. At low concentration, S-doped BiOCl systems are the most stable under Bi-rich growth conditions because of their lower impurity-formation energy. Compared with the electronic structures of S-doped BiOCl, C-or N-doped BiOCl have relatively deeper impurity energy levels appearing in their band gap(except Bi_(36)O_(35)NCl_(36)), which may act as photogenerated carrier-recombination centers and reduce photocatalytic activity. At high concentration, S is substituted on the O lattice site system, whereas some S 3p states mix with the valence band; this mixture leads to an obvious band-gap decrease and continuum-state formation above the valence-band edge of BiOCl. Such activity is advantageous to photochemical catalysis response. Compared with pure Bi OCl and a low-concentration S-doped system, a high-concentration S-doped system shows an obvious redshift on the absorption edge and has better photocatalytic O_2 evolution performance.

Clean production of lactic acid by selective carbon-carbon bond cleavage of biomass feedstock over a novel carbon-bismuth oxychloride photocatalyst

The use of functional materials such as carbon-bismuth oxyhalides in integrated photorefineries for the clean production of fine chemicals requires restructuring.A facile biomass-assisted solvothermal fabrication of carbon/bismuth oxychloride nanocomposites(C/BiOCl)was achieved at various temperatures.Compared with BiOCl and C/BiOCl-120,C/BiOCl-180 exhibited higher crystallinity,wider visible light absorption,and a faster migration/separation rate of photoinduced carriers.For the selective C–C bond cleavage of biomass-based feedstocks photocatalyzed by C/BiOCl-180,the xylose conversion and lactic acid yield were 100%and 92.5%,respectively.C/BiOCl-180 efficiently converted different biomass-based monosaccharides to lactic acid,and the efficiency of pentoses was higher than that of hexoses.Moreover,lactic acid synthesis was favored by all active radicals including superoxide ion(·O_(2)^(−)),holes(h^(+)),hydroxyl radical(·OH),and singlet oxygen(^(1)O_(2)),with·O_(2)^(−)playing a key role.The fabricated photocatalyst was stable,economical,and recyclable.The use of biomass-derived monosaccharides for the clean production of lactic acid via the C/BiOCl-180 photocatalyst has opened new research horizons for the investigation and application of C–C bond cleavage in biomass-based feedstocks.