Xiao-Jing Sang

Two New Armtype Polyoxometalates Grafted on Titanium Dioxide Films: Towards Enhanced Photoelectrochemical Performance.

Two new carboxyethyltin-functionalized polyoxometalates (POMs) were successfully obtained and confirmed with physicochemical and spectroscopic methods including X-ray crystallography. The lowest unoccupied molecular orbitals of both compounds are higher in energy than that of TiO2 , and the optical band gaps of these compounds are smaller than that of TiO2 . Grafting them onto a TiO2 film created two kinds of novel photoanode materials that showed significantly enhanced photovoltaic and photocurrent responses, as well as improved photoelectrooxidation activities for methanol relative to that shown by a single TiO2 film. Further, P2 W15 -Co-SnR produced the largest photocurrent by exploring the photoelectric activities of a series of carboxyethyltin POM derivatives. This work provides new insight into the photoelectrochemical functionalization of POM-based organic-inorganic hybrids.

A new boat-like tungstoarsenate functionalized by carboxyethyltin and its catalytic properties

A new polyoxometalate (POM) estertin derivative, {C(NH2)3}Na10K7[(W4O16){Sn(CH2)2COO}4(B-α-AsW9O33)2]·25H2O (1), has been synthesized from K14[As2W19O67(H2O)]·nH2O ({As2W19}) and Cl3SnCH2CH2COOCH3, which exhibits an unusual boat-like structural feature: four [Sn(CH2)2COO]2+ groups surround a center W4O16 cluster and link two [AsW9O33]9− subunits. 1 shows efficient oxidation catalytic activity and can be applied for mimicking enzyme catalysis.

Extended visible photosensitivity of carboxyethyltin functionalized polyoxometalates with common organic dyes enabling enhanced photoelectric performance

A kind of broad spectral responsive photoelectrode has been assembled from open-chain carboxyethyltin functionalized Dawson sandwich-type polyoxometalates (POMs) [{Sn(CH2)2COO}2M2(P2W15O56)2]16− (SnR-M-P2W15, M = Mn, Co, Cu and Zn) and organic dyes such as rhodamine B (RhB) and methylene blue (MB) through the layer-by-layer (LBL) self-assembly method. SnR-M-P2W15 shows strong adsorption towards RhB and MB. The adsorption capacity of SnR-Co-P2W15 towards RhB and MB reached 217.36 and 288.76 mg g−1 in 10 min, respectively. Compared to Keggin sandwich-type open-chain carboxyethyltin–POM and closed-ring carboxyethyltin–POM derivatives such as [Zn2{Sn(CH2)2COO}2[(PW9O34)2]10− (SnR-Zn-PW9) and [K3{Sn(CH2)2COO}2(PW9O34)2]11− (SnR-PW9), and the parent POMs [M4(H2O)2(P2W15O56)2]16− (M-P2W15, M = Mn, Co, Cu and Zn), SnR-M-P2W15-based photoelectrodes showed significantly enhanced photocurrent owing to their greater visible light harvesting. Also, the photoelectric performances of LBL multilayer films can be adjusted by controlling the number of deposited layers, adsorbed dye types and incorporated transition metal ions in the POMs.

Determination of the stability constant of cobalt-substituted mono-lacunary Keggin-type polyoxometalate and its electrocatalytic water oxidation performance

Abstract The anion form of a cobalt-substituted mono-lacunary Keggin-type polyoxometalate (POM) complex in aqueous solution was identified as [Co(H2O)(H3PW11O39)]2− and its stability constant was determined to be 5.19 × 104 by spectrophotometry. Additionally, the electrocatalytic performances toward water oxidation of different concentrations of [Co(H2O)(H3PW11O39)]2− were investigated in the neutral phosphate buffer solution, and it was found that [Co(H2O)(H3PW11O39)]2− anion itself has little activity; the activity of [Co(H2O)(H3PW11O39)]2− solution actually results from dissociated [Co(H2O)6]2+. This work provides a simple way to understand the origin of catalytic water oxidation activity of a POM-based complex.

Catalytic effects of [Ag(H 2 O)(H 3 PW 11 O 39 )] 3− on a TiO 2 anode for water oxidation

Abstract A [H 3 Ag I (H 2 O)PW 11 O 39 ] 3− -TiO 2 /ITO electrode was fabricated by immobilizing a molecular polyoxometalate-based water oxidation catalyst, [H 3 Ag I (H 2 O)PW 11 O 39 ] 3− (AgPW 11 ), on a TiO 2 electrode. The resulting electrode was characterized by X-ray powder diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Linear sweep voltammetry, chronoamperometry, and electrochemical impedance measurements were performed in aqueous Na 2 SO 4 solution (0.1 mol L −1 ). We found that a higher applied voltage led to better catalytic performance by AgPW 11 . The AgPW 11 -TiO 2 /ITO electrode gave currents respectively 10 and 2.5 times as high as those of the TiO 2 /ITO and AgNO 3 -TiO 2 /ITO electrodes at an applied voltage of 1.5 V vs Ag/AgCl. This result was attributed to the lower charge transfer resistance at the electrode-electrolyte interface for the AgPW 11 -TiO 2 /ITO electrode. Under illumination, the photocurrent was not obviously enhanced although the total anode current increased. The AgPW 11 -TiO 2 /ITO electrode was relatively stable. Cyclic voltammetry of AgPW 11 was performed in phosphate buffer solution (0.1 mol L −1 ). We found that oxidation of AgPW 11 was a quasi-reversible process related to one-electron and one-proton transfer. We deduced that disproportionation of the oxidized [H 2 Ag II (H 2 O)PW 11 O 39 ] 3− might have occurred and the resulting [H 3 Ag III OPW 11 O 39 ] 3− oxidized water to O 2 .