Guilian Zhu

Black brookite titania with high solar absorption and excellent photocatalytic performance

Black platelike brookite with outstanding photocatalytic performance is prepared by constructing a distinct crystalline core/disordered shell structure (TiO2@TiO2−x) through aluminium reduction. Many oxygen vacancies and Ti3+ states are introduced into the distorted shell, which increase the solar energy absorption and boost the photocatalytic activity.

Niobium Nitride Nb4N5 as a New High-Performance Electrode Material for Supercapacitors

Supercapacitors suffer either from low capacitance for carbon or derivate electrodes or from poor electrical conductivity and electrochemical stability for metal oxide or conducting polymer electrodes. Transition metal nitrides possess fair electrical conductivity but superior chemical stability, which may be desirable candidates for supercapacitors. Herein, niobium nitride, Nb4N5, is explored to be an excellent capacitive material for the first time. An areal capacitance of 225.8 mF cm−2, with a reasonable rate capability (60.8% retention from 0.5 to 10 mA cm−2) and cycling stability (70.9% retention after 2000 cycles), is achieved in Nb4N5 nanochannels electrode with prominent electrical conductivity and electrochemical activity. Faradaic pseudocapacitance is confirmed by the mechanistic studies, deriving from the proton incorporation/chemisorption reaction owing to the copious +5 valence Nb ions in Nb4N5. Moreover, this Nb4N5 nanochannels electrode with an ultrathin carbon coating exhibits nearly 100% capacitance retention after 2000 CV cycles, which is an excellent cycling stability for metal nitride materials. Thus, the Nb4N5 nanochannels are qualified for a candidate for supercapacitors and other energy storage applications.

Gray TiO2 nanowires synthesized by aluminum-mediated reduction and their excellent photocatalytic activity for water cleaning.

Not always black and white: Gray TiO2 nanowires with high photocatalytic activity have been successfully synthesized by aluminum-mediated reduction in a two-zone furnace. These wires, which possess a core (TiO(2-x))/shell (TiO2 ) structure, exhibit visible-light and even IR absorption with high photocatalytic activity, far exceeding that of commercial Degussa P25. They show high stability in air and water under solar-light irradiation.

Black Titania for Superior Photocatalytic Hydrogen Production and Photoelectrochemical Water Splitting

To utilize visible‐light solar energy to meet environmental and energy crises, black TiO2 as a photocatalyst is an excellent solution to clean polluted air and water and to produce H2. Herein, black TiO2 with a crystalline core–amorphous shell structure reduced easily by CaH2 at 400 °C is demonstrated to harvest over 80 % solar absorption, whereas white TiO2 harvests only 7 %, and possesses superior photocatalytic performances in the degradation of organics and H2 production. Its water decontamination is 2.4 times faster and its H2 production was 1.7 times higher than that of pristine TiO2. Photoelectrochemical measurements reveal that the reduced samples exhibit greatly improved carrier densities, charge separation, and photocurrent (a 4.5‐fold increase) compared with the original TiO2. Consequently, this facile and versatile method could provide a promising and cost‐effective approach to improve the visible‐light absorption and performance of TiO2 in photocatalysis.

Gray Ta2O5 Nanowires with Greatly Enhanced Photocatalytic Performance

Black TiO2, with enhanced solar absorption and photocatalytic activity, has gained extensive attention, inspiring us to investigate the reduction of other wide-bandgap semiconductors for improved performance. Herein, we report the preparation of gray Ta2O5 nanowires with disordered shells and abundant defects via aluminum reduction. Its water decontamination is 2.5 times faster and hydrogen production is 2.3-fold higher over pristine Ta2O5. The reduced Ta2O5 also delivers significantly enhanced photoelectrochemical performance compared with the pristine Ta2O5 nanowires, including much higher carrier concentration, easier electron-hole separation and 11 times larger photocurrent. Our results demonstrate that Ta2O5 will have great potentials in photocatalysis and solar energy utilization after proper modification.

Black nanostructured Nb2O5 with improved solar absorption and enhanced photoelectrochemical water splitting

Black TiO2, with increased solar light absorption and enhanced photocatalytic and photoelectrochemical (PEC) performance, has attracted enormous attention, stimulating us to explore the blackening of other oxide semiconductors for enhanced properties. Here, we report the fabrication of black nanostructured Nb2O5 and its enhanced PEC properties for the first time. We successfully prepared oxygen-deficient black Nb2O5 nanochannels, which contain a considerable amount of oxygen vacancies (Nb4+ sites) serving as shallow donors. Black Nb2O5 exhibits strong visible and infrared light absorption, which can absorb 75.5% solar energy, which is superior to 5.7% for pristine Nb2O5. The PEC performance of black Nb2O5 photoanodes is significantly enhanced with a relatively large photocurrent of 1.02 mA cm−2 and a high applied bias photon-to-current efficiency (ABPE) of 0.345%, in comparison with the poor performance of pristine Nb2O5 (0.084 mA cm−2 photocurrent and 0.056% ABPE). These results indicate that black Nb2O5 is a promising material for PEC application and solar energy utilization.

Molten salt assisted synthesis of black titania hexagonal nanosheets with tuneable phase composition and morphology

A facile, high yield ZnCl2/KCl molten-salt route is developed to fabricate black titania hexagonal nanosheets under atmospheric pressure and low temperature (400 °C). After post-annealing, the black titania possesses a tunable phase composition and enhanced visible light photocatalytic activity, accompanied with a controllable morphology transformation from hexagonal nanosheets to nanorods.

Black strontium titanate nanocrystals of enhanced solar absorption for photocatalysis

Black titania has attracted enormous attention due to its enhanced photocatalytic activity via increased solar absorption, but few studies extended the investigations to other wide band-gap titanates. Herein, strontium titanate (SrTiO3), a typical ternary titanate with more potential in photocatalysis, is selected as the target material. Black SrTiO3 nanocrystals were obtained by molten aluminum reduction of solution-processed pristine SrTiO3 in a two-zone furnace. Different from the black titania, black SrTiO3 nanocrystals are well-crystallized and have no core–shell structure. Substantial Ti3+ cations and oxygen vacancies are introduced into SrTiO3 after aluminum reduction, which results in enhanced absorption in both visible and near-infrared regions, and improved charge separation and transport. The photocatalytic hydrogen-generation and photoelectrochemical investigations demonstrate that black SrTiO3 exhibits an impressive improvement (2.5 times and 2.4 times at 1.23 VRHE, respectively) compared with white SrTiO3.