A Convenient Procedure for Preparing BiOX-TiO2 Photoelectrocatalytic Electrodes from a Titanium-Oxo Compound-Modified Carbon Fiber Cloth.

Photoelectrocatalysis (PEC) has shown great advantages in sustainable organic synthesis and wastewater treatment because the PEC process can minimize electron-hole recombination, thereby improving the photocatalytic performance. Here, we report a convenient procedure for preparing immobilized BiOX-TiO2 photoelectrocatalytic electrodes from a titanium-oxo compound (TOC)-modified carbon fiber cloth (CFC). Crystalline TOCs composed of Ti12 cations and bismuth halide anions, [Ti12O14(OiPr)18][Bi3Br11(THF)2] (1) and [Ti12O14(OiPr)18][Bi4I14(THF)2] (2), were grown on CFC. Taking advantage of the easy hydrolysis of the titanium-oxo cation and bismuth halide anion, we could easily transform these CFC-immobilized crystals into BiOX-TiO2/CFC (X = Br or I) photocatalysts, which facilitates recycling of the catalysts. The photocatalytic dye degradation test showed that the efficiency did not decrease obviously after 10 photocatalytic cycles. Using BiOX-TiO2-modified CFC as electrodes, electrocatalysis (EC), photocatalysis (PC), and PEC were examined. PEC showed an attractive synergistic effect of EC and PC. These TOC-modified CFCs would be potential candidates for catalytic electrodes for sustainable wastewater purification.

Mono- and Bismetalphenanthroline-Substituted Ti12 Clusters: Structural Variance and the Effect on Electronic State and Photocurrent Property.

Despite the numerous titanium-oxo clusters (TOCs) which have been reported, the nature of small clusters (nuclearity < 10) as model compounds showed large deviation from that of nanoscale TiO materials. Therefore, theoretical and experimental studies for large TOCs merit more attention. We recently prepared and crystallographically characterized a series of large TOCs: Ti11O15(OiPr)16(Cophen) (1), Ti11O15(OiPr)16(Mnphen) (2), Ti10O14(OEt)16(Mnphen)2 (3), and Ti10O14(OEt)16(Mnphphen)2 (4) (phen = 1,10-phenanthroline, phphen = 4,7-biphenyl-phen). These compounds are derivatives of a Ti12 parent cluster by replacing one or two of the five-coordinated titanium atoms of the Ti12 cluster with a transition metal M, Co(II) and Mn(II), that is chelated by a phen group. The effects of mono- and bis-substituted Mphen on the charge and structure of the clusters are discussed. Theoretical evaluation of the frontier orbitals of the clusters is carried out on the basis of the precisely defined crystal structures. Different from the dye molecule to TiO core charge transfer for the dye-modified TOCs, charge transfer in these clusters is from TiO/TiOM to phen/Mphen. The effects of different metal ions and the number of substituted Mphen moieties on the photocurrent properties are evaluated. The results will be of interest to research on cluster chemistry, especially on the TOC chemistry.

Assembly of a Titanium-Oxo Cluster and a Bismuth Iodide Cluster, a Single-Source Precursor of a p-n-Type Photocatalyst.

Titanium oxides and bismuth halides or oxyhalides have been known to be excellent semiconductors with both excellent photocatalytic and photoelectric properties. The design of supersalts assembled by titanium-oxo clusters (TOCs) and bismuth iodide clusters is a hopeful strategy for exploring the chemistry and application of new titanium-oxo clusters. We report herein a series of unusual ionic TOCs with Ti12 oxo cluster cations and bismuth iodide anions, [Ti12O15(OiPr)17]3[Bi3I12] (Bi3), [Ti12O14(OiPr)18][Bi4I14(THF)2] (Bi4), and [Ti12O14(OiPr)18][Ti11BiO14(OiPr)17][Bi6I22] (Bi6). Single-crystal X-ray analysis revealed that the type and charge of the Ti12 clusters varied with the charges of different bismuth iodide clusters. Taking advantage of the easy hydrolysis of the TOCs and BiI clusters in water, we used these supersalt crystals as single-source precursors to prepare a p-n-type BiOI-TiO photocatalyst. The heterojunction materials were carefully characterized by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, etc. The synergistic effect of the two components of BiOI and TiO on the photocatalytic degradation of RhB in water is demonstrated. This is a very convenient method for obtaining a p-n-type BiOI-TiO heterojuction photocatalyst by just placing the ground TOC crystals into water.

Molybdenum-titanium oxo-cluster, an efficient electrochemical catalyst for the facile preparation of black titanium dioxide film.

Black-TiO2 has become increasingly interesting as a promising photoactive material. Most of the preparations for black-TiO2 involve either high temperature calcination, plasma, lengthy chemical reactions or dealing with dangerous or toxic chemicals. We found, by accident, that Mo-Ti oxo-clusters are efficient catalysts for the hydrogenation of a TiO2 electrode to black-TiO2 at room temperature. A series of Mo-Ti oxo-clusters, [Ti4Mo4O10(OR)14(X-BA)2] (BA = benzoate, X = H (1), F (2), Cl (3), and Br (4)), were prepared and were characterized by crystallography. They have a Mo4Ti4 structure with Mo(v)-Mo(v) metal-metal interactions. The activated hydrogen (H*) generated by electrochemically catalytic water splitting turns the TiO2 electrode to black-TiO2 at room temperature, due to the reduction of Ti(iv) to H+Ti(iii). The potentials applied for water reduction must generally be higher than the overpotential at the TiO2 electrode (-1.0 V vs. RHE). In this work, the onset potential of hydrogen evolution significantly decreased to -0.1 V vs. RHE. Using this blackened 1-TiO2 electrode, the effective electrochemical catalytic degradation of a dye was examined in comparison with the degradation using the white TiO2 electrode. This work provides a method for the facile preparation of a black-TiO2 film, and is a step forward in black-TiO2 research.

Eu-phen Bonded Titanium Oxo-Clusters, Precursors for a Facile Preparation of High Luminescent Materials and Films.

Incorporation of Eu complexes into various organic or inorganic matrixes is one of the acceptable strategies to obtain displaying materials having practical applications. In this work, we report a convenient approach to preparing high luminescent organic-inorganic hybrid materials and films from the europium-titanium oxo-clusters (EuTOCs) having photoactive antenna ligands. Three Eu2Ti4 oxo-clusters were synthesized and crystallographically characterized. They are the first reported lanthanide-TOCs coordinated with 1,10-phenanthroline (phen) and 2,2'-bipyridine (bpy) as photoactive ligands, Eu2Ti4O6(phen)2(pa)10 (1) (pa = propionate), Eu2Ti4O6(bpy)2(pa)10 (2), and Eu2Ti4O6(phen)2(MA)10 (3) (MA = methacrylate). Benefitting from the photoactive antenna ligands and the rigid cluster structures, these clusters showed bright red luminescence with quantum yield in the range of 60-80% and long lifetime up to 3.0 ms. Unlike those physically mixed polymeric materials, the MA coordinated compound 3 can be self-polymerized to form a brilliant luminescent film. The film coated slide was used to develop a fluorescence sensor for biomolecule ascorbic acid (AA). The low detection limit and reusable properties suggest great potential for such EuTOC films in real applications.