Zhixia Sun

Enhanced photovoltaic response by incorporating polyoxometalate into a phthalocyanine-sensitized electrode

A photovoltaic electrode material consisting of cobalt tetraaminophthalocyanine (CoTAPc) and Dawson-type phosphomolybdate (P2Mo18) was fabricated through the layer-by-layer (LbL) assembly method. The film electrode was characterized by UV–vis spectroscopy, IR spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and photoelectrochemical measurements. Photovoltaic measurement of the film electrode under light irradiation of 365 nm demonstrated that the P2Mo18/CoTAPc composite film electrode exhibits higher photocurrent and power conversion efficiency (η) than the phthalocyanine-only electrode, furthermore the increased photocurrent of (P2Mo18/CoTAPc/PSS/PAH)5 is not equal to the direct photoresponse addition of P2Mo18 and CoTAPc. Based on the results of fluorescence quenching measurements, the enhanced photovoltaic effect should be attributed to the occurrence of the photoinduced electron transfer between CoTAPc and POM, which increases the efficient dissociation of excited electron–hole pairs (excitons). The present research represents the first example of enhancing the photovoltaic response of organic photovoltaic materials by the assistance of polyoxometalates.

Enhanced electrochromic performance of composite films by combination of polyoxometalate with poly(3,4-ethylenedioxythiophene)

A composite film containing poly(3,4-ethylenedioxythiophene) (PEDOT), polyoxometalate (POM) clusters K6P2W18O62·14H2O (P2W18) and polyallylamine hydrochloride (PAH) was fabricated by a smart combination of layer-by-layer (LbL) with electro-polymerization methods. The composite film displays enhanced electrochromic performance by incorporation of P2W18 into the PEDOT film. The electrochromic property of the film is significantly improved, resulting in an optical contrast of 54.7% at 600 nm and an absorbance that does not change after 1500 cycles. Additionally, the film provides broader absorption throughout the visible region. These results demonstrate the essential role of POMs in improving functionality on PEDOT for applications in electrochromic devices.

Enhanced photovoltaic response of the first polyoxometalate-modified zinc oxide photoanode for solar cell application

A photovoltaic electrode consisting of polyoxometalate (SiW12) and zinc oxide (ZnO) was fabricated on indium tin oxide (ITO) glass by one-step electrodeposition. The addition of SiW12 strongly influences the morphology and crystallographic orientation of the ZnO. The photovoltaic properties of the ZnO film and the SiW12–ZnO composite films were investigated via solar cell assembly. Both transient photocurrent and current–voltage curve measurements demonstrate that the photocurrent and power conversion efficiency of the SiW12–ZnO composite film were markedly enhanced in comparison with that of the ZnO film. Based on the results of fluorescence quenching measurements, the enhanced photovoltaic effect should be attributed to the occurrence of the photoinduced electron transfer between polyoxometalate and ZnO, which increases the efficient dissociation of excited electron–hole pairs (excitons).

Synergistic enhancement of photovoltaic performance of TiO2 photoanodes by incorporation of Dawson-type polyoxometalate and gold nanoparticles

To explore the synergistic effects of polyoxometalate and noble metal nanoparticles on the photovoltaic performance of titanium dioxide (TiO2), multilayer film photoanodes consisting of TiO2 nanoparticles, gold nanoparticles (Au) and Dawson-type polyoxometalate K6P2W18O62 (abbr. as P2W18) have been prepared by the layer-by-layer self-assembly method, and poly(styrenesulfonate) (PSS) was used as a film forming auxiliary material. These film electrodes were characterized by UV-vis spectra, X-ray photoelectron spectroscopy, atomic force microscopy, and photoelectrochemical measurements. Transient photocurrent and current–voltage curve measurements demonstrate that the photocurrent response and power conversion efficiency increase in the sequence: the TiO2 film < the P2W18/TiO2 film < the TiO2/P2W18/Au film. These results provide valuable information for photovoltaic and photoelectrochemical applications.

Enhanced photocatalytic H2 evolution on CdS with cobalt polyoxotungstosilic and MoS2/graphene as noble-metal-free dual co-catalysts

An efficient photocatalyst was designed through dual modification of CdS by cobalt polyoxotungstosilic (SiW11Co) and MoS2/graphene (M/G). The activity of CdS is increased up to 21.3 times with 1 wt% SiW11Co and 5 wt% M/G loaded. In the absence of noble metals, the as-prepared sample reached a H2 evolution rate of 1.7 mmol h−1.

Enhanced photoconductivity of a polyoxometalate–TiO2 composite for gas sensing applications

A photoconductive device of phosphotungstic acid (denoted as PW12) and TiO2 composite was fabricated. Compared to pristine TiO2, the composite materials of PW12–TiO2 displayed a remarkable enhancement (ca. 2000-fold) in their photocurrent values. Furthermore, the composite materials also exhibited good gas sensing performance for acetone.

A 3D all-inorganic architecture based on the [H2W12O42]10− building block with different alkaline-earth metal linkers: crystal structures, surface photovoltage and photoluminescent properties

Three-dimensional (3D) all-inorganic polyoxometalate compounds, Ca2Na6[H2W12O42]·30H2O (1), Sr4H2[H2W12O42]·26H2O (2), Sr4Na2[H2W12O42]·30H2O (3) and Ba4Na2[H2W12O42]·29.5H2O (4) have been synthesized and their structures consist of [H2W12O42]10− building units and alkaline-earth metal cations (Ca2+, Sr2+ and Ba2+) as linkers. The most interesting feature is that compound 2 represents the first example of a 3D all-inorganic framework in which the paradodecatungstate-B anions [H2W12O42]10− were linked by pure alkaline-earth metal cations. Moreover, each [H2W12O42]10− building unit in compound 2 acts as a decadentate ligand coordinated with ten Sr2+ ions, which represents the highest coordination number of [H2W12O42]10− with alkaline-earth metal cations so far. Another interesting feature is that compounds 1–4 exhibit a clear response to surface photovoltage and electric field-induced surface photovoltage, which is indicative of the semiconductor property and suggests these compounds have potential applications as photocatalysts and light-to-electricity conversion materials.

Photovoltaic performance enhancement of Cu2O photocathodes by electrostatic adsorption of polyoxometalate on Cu2O crystal faces

A novel incorporation of polyoxometalate (POM) into Cu2O photocathodes was achieved by electrostatic adsorption of polyoxometalate on Cu2O crystal faces, so that the Cu2O/POM composite films exhibit significant photovoltaic enhancement because the POM could act as electron-acceptor to retard the electron–hole recombination and facilitate the photoexcited electron transfer.

Synergetic effect of polyoxoniobate and NiS as cocatalysts for enhanced photocatalytic H2 evolution on Cd0.65Zn0.35S

Composite photocatalyst K7HNb6O19–NiS/Cd0.65Zn0.35S is demonstrated to be highly active for H2 evolution under visible light due to the introduction of K7HNb6O19 and NiS as cocatalysts. In the absence of noble metals, a high quantum yield of 42% was achieved at 420 nm.

Improving TiO2 photoanodes through silver–polyoxotungstate nanohybrids: toward photovoltaic and photoelectrocatalytic application

In this work, a TiO2 photoanode was modified through Ag–POT (polyoxotungstate K6P2W18O62 abbr. as POT, silver–POT nanohybrids abbr. as Ag–POT) to improve the photovoltaic and photoelectrocatalytic performance. A facile in situ preparation of Ag nanoparticles was achieved by using POT as both a reductant and capping agent. Transient photocurrent and current–voltage curve measurements demonstrate that both the photocurrent response and power conversion efficiency of the Ag–POT/TiO2 film were markedly enhanced in comparison with that of the TiO2 only film and the POT/TiO2 film. Moreover, the Ag–POT/TiO2 film exhibited significant photoelectrocatalytic oxidation activity of dopamine. These results suggest their potential applications in photovoltaics as well as photoelectrocatalysis.