Search

Existing literature has examined the contextual effects on individual environmental activism, but little research has been conducted to investigate how local-level governance factors affect individ...

The poor surface charge separation and transfer properties as well as sluggish water oxidation kinetics jointly limit the performance of BiVO4 photoanode for water oxidation. In this work, p-type CuCoO2 with high-spin Co3+(Oh) was investigated as co-catalyst to synergistically improve the surface charge separation and transfer efficiencies as well as reaction kinetics of BiVO4 film for photoelectrochemical water oxidation. In comparison with the photocurrent on BiVO4 photoanode for water oxidation (1.21 mA/cm2 at 1.23 V vs. RHE), the CuCoO2-coupled BiVO4 (CuCoO2/BiVO4) photoanode exhibits a higher photocurrent density of 3.32 mA/cm2 at 1.23 V vs. RHE under AM 1.5G illumination. In addition, a significant improvement on the reaction stability is achieved on the CuCoO2/BiVO4 photoanode, about ∼79% water oxidation activity is retained on the CuCoO2/BiVO4 photoanode after operating at 0.8 V vs. RHE for 5 h, while only ∼9% activity is retained on the BiVO4 photoanode. The boosted water oxidation activity and stability on CuCoO2/BiVO4 photoanode could be attributed the synergistic effect that originated from CuCoO2-electrocatalysis and BiVO4-photocatalysis in thermodynamics and kinetics. Specifically, p-n heterojunctions are formed in the coupling interface between CuCoO2 (p-type) and BiVO4 (n-type), which thermodynamically improve the surface charge separation and transfer efficiencies of BiVO4 photoanode during water oxidation. Simultaneously, the high-spin Co3+(Oh) of CuCoO2 could act as active sites to accelerate the water oxidation of CuCoO2/BiVO4 photoanode in kinetics. In addition, Cu2+ active sites are formed for water oxidation through the oxidation reaction of photogenerated holes with the Cu+ of CuCoO2.

Manipulation of interfacial charge separation and transfer is one of the primary breakthroughs to improve the water oxidation activity and stability of BiVO4 photoanode. In the present work, a CoMoO4-coupled BiVO4 (BiVO4/CoMoO4) film was designed and prepared as the photoanode for photoelectrochemical (PEC) water oxidation. Compared with the bare BiVO4 film, obviously improved PEC water oxidation performance was observed on the BiVO4/CoMoO4 film. Specifically, a higher water oxidation photocurrent density of 3.04 mA/cm2 at 1.23 V versus RHE was achieved on the BiVO4/CoMoO4 photoanode, which is of about 220% improvement over bare BiVO4 photoanode (1.34 mA/cm2 at 1.23 V vs RHE). In addition, the BiVO4/CoMoO4 film photoanode was of better stability and faster hole-to-oxygen kinetics for water oxidation, without significant activity attenuation for 6 h of reaction at 0.65 V versus RHE. The enhanced water oxidation performance on the BiVO4/CoMoO4 film photoanode can be ascribed to the synergistic effect of the...

High surface states induced photoelectrochemical (PEC) activity and stability issue is the major performance bottleneck for nanostructured WO3 photoanode. Here we report that amorphous TiO2 (α-TiO2) be used as passivator to modify the surface states of WO3 nanoflakes film for improving its PEC water oxidation performance. In comparison with bare WO3 film, the α-TiO2-coupled WO3 (α-TiO2/WO3) film is of higher PEC water oxidation activity and stability. The photocurrent on α-TiO2/WO3 film photoanode is improved by 2 times that reached 1.4 mA/cm2 in 0.1 M Na2SO4 solution at 0.8 V (vs. SCE). After α-TiO2 coupling, the UV–vis absorption edge and intensity of WO3 film do not change obviously, but the formation and oxidation kinetics of H2O2 on WO3 photoanode are modified. The density functional theory calculations indicate the monoclinic WO3(002) has a surface energy of 1.17 J/m2, whereas the α-TiO2/WO3(002) with a much lower surface energy of 0.3 J/m2. Additionally, the length of Ti O bond of α-TiO2 is changed from the initial 1.929 A to a shorter length of 1.886 A and a longer length of 2.290 A in α-TiO2/WO3(002) through the O2--W6+ bonding effect at α-TiO2/WO3 interface. Therefore, the enhanced PEC water oxidation performance on α-TiO2/WO3 film can be attributed to that α-TiO2 passivates the surface states of WO3 nanoflakes film, and the formation of H2O2 from the photoexcited-electrons/dissolved-oxygen route is depressed and the PEC oxidation of H2O2 is accelerated.

Poor charge transfer and separation rate are the major bottlenecks for the activity and stability of BiVO4 photoanode. Here, we introduced oxygen vacancies into MoO3/BiVO4 heterojunction film by post-annealing the film in argon-saturated environment for improving its photoelectrochemical (PEC) water oxidation activity and stability. In comparison with the normal MoO3/BiVO4 film, the MoO3/BiVO4 film with oxygen vacancies is of better PEC water oxidation performance. Specifically, a higher photocurrent density of 4.1 mA/cm2 in 0.1 M Na2SO4 at 1.1 V versus SCE was achieved on the MoO3/BiVO4 film with oxygen vacancies, which is about 200% improved over the normal MoO3/BiVO4 film (1.83 mA cm−2, at 1.1 V versus SCE). In addition, the MoO3/BiVO4 film with oxygen vacancies shows more stable activity and faster kinetics for water oxidation, without significant activity loss for 5 h reaction at 1.23 V versus RHE. The enhanced performance on such a MoO3/BiVO4 film photoanode can be attributed to that the oxygen vacancies accelerate the charge transfer and separation rate between film/electrolyte interface, and thus improve the water oxidation activity and restrain the anodic photocorrosion simultaneously.

BiVO4 is a promising photoanode material for photoelectrochemical water splitting, but its actual activity is hindered by the high energy surface states. Here, we report that In3+ can be used as a dopant to substitute the partial sites of Bi3+ in BiVO4 for modifying the surface states and improving the water oxidation activity of a BiVO4 nanoflake film. Among the In3+-doped BiVO4 film photoanodes, the 7% In3+-doped BiVO4 film shows optimal photoelectrochemical water oxidation activity. At 1.23 V vs. RHE, the 7% In3+-doped BiVO4 photoanode exhibits a photocurrent density of 1.56 mA cm−2 in 0.1 M Na2SO4, which is over 200% greater than that of the undoped BiVO4 photoanode. In3+-doping did not change the morphology, phase and band gap of BiVO4 obviously, but resulted in a positive shift of the flat band position and higher surface charge separation efficiency for water oxidation. Density functional theory calculations indicate that the surface energy of BiVO4 decreased after In3+-doping that involved more unsaturated electrons of the Bi atom in the Bi–O bonds, thus reducing the amount of exposed unsaturated Bi atoms and broken Bi–O bonds. Therefore, the enhanced water oxidation activity on the In3+-doped BiVO4 photoanode can be ascribed to In3+-doping that passivated the surface states of BiVO4 and thus inhibited the surface charge recombination.

In this paper we propose a new type of receiver for underwater acoustic communication. The proposed receiver has the following features: 1) It has a turbo structure with an embedded adaptive decision feedback equalizer (DFE), which is based on the least-symbols-error-rate criterion and is shown to outperform the conventional minimum mean square error (MMSE) equalizers; 2) By exploiting the training symbol at the beginning and at the end of a data frame, the proposed receiver employs time-reversal equalization to suppress the error propagation of the applied DFE, where the time-reversal diversity gain is exploited by combing the output of the bidirectional DFE with an equal-gain combing scheme; and 3) A receiving array is applied, where the output of each hydrophone is individually equalized and then the equalizer outputs are combined with an equal-gain combing scheme. The proposed receiver is extensively evaluated through computer simulation and field experiments, and is also compared with the conventional MMSE based receiver in terms of the bit error rate performance.

A MoO 3 /BiVO 4 heterojunction film consisting of dispersed nano-MoO 3 on the surface of BiVO 4 nanoflake was constructed for photoelectrochemical water oxidation. In comparison with bare BiVO 4 and MoO 3 film, the MoO 3 /BiVO 4 heterojunction film shows enhanced water oxidation activity. At 0.8 V vs. SCE, the photocurrent on the optimal MoO 3 /BiVO 4 heterojunction film increases by up to about 6 times compared to that on the bare BiVO 4 film. The conduction and valence band potential of MoO 3 are found to be more positive than those of BiVO 4 , and the electric conductivity for MoO 3 and BiVO 4 is on the order of 10 −6 S cm −1 and 10 −9 S cm −1 , respectively. Thus, the origin of enhanced water oxidation activity on the MoO 3 /BiVO 4 heterojunction film can be primarily ascribed to the band potential and conductivity differences between MoO 3 and BiVO 4 , which are advantageous for separating and transferring the surface charge of BiVO 4 .

The development of biomimetic catalysis for efficient photoreduction of CO2 is an effective alternative to address energy problems. However, amelioration on the construction of biomimetic catalysts for elevated photocatalytic performance is still challenging and demanded. Herein, a bioinspired artificial photosynthesis system is constructed based on ZrO2 nanoframes (ZFs) and metalloporphyrin to mimic the morphology of trees. The robust backbone of the framework and the bio-inspiring porphyrins anchored on the surface of ZFs function as the strong trunk and well-ordered leaves of a tree, respectively. The biomimetic system achieves an evolution yield of 35.3 μmol during 3 h reaction with 93.1% CO selectivity and 1.84% CO apparent quantum efficiency (A.Q.E.), which is about 60.8 times larger than that of pure porphyrin (Ni) (0.58 μmol). Detailed analysis reveals that the catalytic system could not only achieve fast separation of the photogenerated carriers and effective CO2 activation but also possess suitable energy levels, which could efficiently transfer electrons to the Ni catalytic sites to improve the photocatalytic activity. Furthermore, the good recycling tests could be explained by the robust supporting of frameworks as well as the strong binding of the Zr atoms and carboxyl groups of porphyrins. This work presents a simple model of biomimetic catalysts and outlines possible strategies for other biomimetic manufactures.

Increasing distributed rooftop solar photovoltaic generation in the southern California coast necessitates accurate solar forecasts. In summertime mornings marine boundary layer stratocumulus commonly covers the southern California coast. The inland extent of cloud cover varies primarily depending on the temperature inversion base height (IBH, i.e. boundary layer height) and topography as confirmed using radiosonde sounding measurement and satellite irradiance data. Most operational numerical weather prediction models consistently overestimate irradiance and underpredict cloud cover extent and cloud thickness, presumably due to an underprediction of IBH. A thermodynamic method was developed to modify the boundary layer temperature and moisture profiles to better represent the boundary layer structure in the Weather and Research Forecasting model (WRF). Validation against satellite global horizontal irradiance (GHI) demonstrated that the best IBH ensemble improves GHI accuracy by 23% mean absolute error compared to the baseline WRF model and is similar to 24-h persistence forecasts for coastal marine layer region. The spatial error maps showed deeper inland cloud cover. Validation against ground observations showed that IBH ensembles were able to outperform persistence forecast at coastal stations.

Due to high electrocatalytic activity, Ag nanoparticles (Ag NPs) always be a good candidate for electrochemical sensors. However, it suffers from the aggregation problem during synthesis, storage and immobilization process. In this paper, hierarchical Sn3O4 was selected as scaffold for Ag NPs to prevent aggregation and ensure the stability. As a sensitive electrode to detect H2O2, Ag/Sn3O4 exhibits wide linear range and reliable stability, which can be attributed to the hierarchical structure, strong immobilization of Ag NPs and structural, physical and chemical stability of Sn3O4 scaffold. It was concluded that the hierarchical Ag/Sn3O4 architecture has potential applications in the design of nonenzymatic H2O2 sensors and the load of Ag NPs on heterovalent tin oxides demonstrates a promising way for building H2O2 detection electrodes.

The New Goddard shortwave (SW) radiation scheme of the Weather Research and Forecasting (WRF) numerical weather prediction model leads to positive biases in the clear-sky downwelling SW radiation (also referred to as global horizontal irradiance, GHI). Clear-sky GHI is attenuated primarily by four atmospheric constituents: (i) ozone (ii) background gases (e.g., trace gases), (iii) precipitable water and, (iv) aerosols. The effect of each constituent in the New Goddard SW scheme is isolated here by subtracting from the GHI predicted for an atmosphere that lacks one constituent, the GHI predicted for an atmosphere with all the constituents. Compared with the WRF’s Rapid Radiative Transfer Model for Global Circulation Models (RRTMG), the main contributions to the clear-sky irradiance bias in the New Goddard SW scheme come from modeling issues with the absorptions by water vapor and ozone. Enhancing the absorption due to water vapor continuum and using the RRTMG’s ozone profiles in the New Goddard SW scheme improved the agreement with the WRF’s RRTMG predictions for both GHI and direct normal irradiance. These results are further confirmed with the REST2 radiative transfer model.

In this paper, the turbo principle is applied to the existing least symbols error rate(LSER) decision feedback equalization(DFE) for underwater channel. The performance of the DFE adaptive algorithms are aided by soft information delivered from the channel decoder. We introduce a variable step size scheme that takes soft information into account to get the more suitable step size which can reduce the impact of an unreliable fed-back symbol. The simulation results show that the proposed scheme obtains more than 2dB gain at the bit error rate level of 10−5, compared with existing method.

Integration of forecasting of solar energy feed-in to the electric network is becoming essential because of its continually increasing penetration level. Three-dimensional numerical weather prediction (NWP) models predict the weather based on the current weather conditions (called initialization) and simulate of the ensuing atmospheric processes. The accuracy of forecasts therefore depend, in part, on the accuracy of the model initializations. Data assimilation is recognized as the most widely used technique to improve the initialization into NWP models. In specific, meteorological observations from the surface and upper-air in-situ networks over the southern California coast are assimilated into the Weather Research and Forecasting (WRF) model. It is found that the global horizontal irradiance (GHI) produced by WRF data assimilation experiments are significantly closer to the observations as compared to the standard WRF forecast. Especially, the GHI biases are reduced significantly during the morning hours.