Electronic Characteristics, Stability and Water Oxidation Selectivity of High-Index BiVO4 Facets for Photocatalytic Application: A First Principle Study

Some high-index facets of BiVO₄, such as (012), (210), (115), (511), (121), (132) and (231), exhibit much better photocatalytic performance than conventional (010) and (110) surfaces for water splitting. However, the detailed mechanisms and stability of improved photocatalytic performance for these high-index BiVO₄ surfaces are still not clear, which is important for designing photocatalysts with high efficiency. Here, based on first principle calculation, we carried out a systematic theoretical research on BiVO₄ with different surfaces, especially high-index facets. The results show that all of the high-index facets in our calculated systems show an n-type behavior, and the band edge positions indicate that all of the high-index facets have enough ability to produce O₂ without external bias. Electronic structures, band alignments and formation enthalpy indicate that (012), (115) and (132) could be equivalent to (210), (511) and (231), respectively, in the calculation. Oxidation and reduction potential show that only (132)/(231) is stable without strongly oxidative conditions, and the Gibbs free energy indicates that (012)/(210), (115)/(511), (121) and (132)/(231) have lower overpotential than (010) and (110). Our calculation is able to unveil insights into the effects of the surface, including electronic structures, overpotential and stability during the reaction process.

Electrostatic Field Enhanced Photocatalytic CO2 Conversion on BiVO4 Nanowires

The recombination loss of photo-carriers in photocatalytic systems fatally determines the energy conversion efficiency of photocatalysts. In this work, an electrostatic field was used to inhibit the recombination of photo-carriers in photocatalysts by separating photo-holes and photo-electrons in space. As a model structure, (010) facet-exposed BiVO₄ nanowires were grown on PDMS-insulated piezo-substrate of piezoelectric transducer (PZT). The PZT substrate will generate an electrostatic field under a certain stress, and the photocatalytic behavior of BiVO₄ nanowires is influenced by the electrostatic field. Our results showed that the photocatalytic performance of the BiVO₄ nanowires in CO₂ reduction in the negative electrostatic field is enhanced to 5.5-fold of that without electrostatic field. Moreover, the concentration of methane in the products was raised from 29% to 64%. The enhanced CO₂ reduction efficiency is mainly attributed to the inhibited recombination loss of photo-carriers in the BiVO₄ nanowires. The increased energy of photo-carriers and the enhanced surface absorption to polar molecules, which are CO in this case, were also play important roles in improving the photocatalytic activity of the photocatalyst and product selectivity. This work proposed an effective strategy to improve photo-carriers separation/transfer dynamics in the photocatalytic systems, which will also be a favorable reference for photovoltaic and photodetecting devices.

The effect of Fe(iii) ions on oxygen-vacancy-rich BiVO4 on the photocatalytic oxygen evolution reaction

The surface oxygen vacancies could promote the photocatalytic O2 evolution of BiVO4. Simultaneously, Fe3+ ions in solution could facilitate the holes' transfer to improve the water oxidation reaction.

Cl- modification for effective promotion of photoelectrochemical water oxidation over BiVO4

Postsynthetic treatment is an attractive method to enhance photoelectrochemical water splitting. The facile Cl^- modification approach developed in this work remarkably promotes the photocurrent density of BiVO₄ up to 2.7 mA cm^-2 by facilitating carrier transfer in addition to a charge carrier separation efficiency enhancement.

Ultrafine SnO2/010 Facet-Exposed BiVO4 Nanocomposites as Efficient Photoanodes for Controllable Conversion of 2,4-Dichlorophenol via a Preferential Dechlorination Path

It is a great challenge for achieving efficiently controllable conversion of chlorinated organics through BiVO₄-based photoelectrochemical methods by improving the selective adsorption of such organics and charge separation. Herein, we have successfully fabricated SnO₂/010 facet-exposed BiVO₄ nanocomposites by a series of hydrothermal processes and further used as efficient photoanodes. The resulting photoanode exhibits about 6.3 times higher photoelectrochemical activity than bulk-BiVO₄, especially with the efficiently controllable conversion of 2,4-dichlorophenol (2,4-DCP) to the nontoxic valuable intermediates such as catechol and pyrogallol by preferential dechlorination. Based on the 2,4-DCP adsorption curves, in situ diffuse reflectance infrared spectra, transient-state surface photovoltage responses, and photocurrent action spectra, it was clearly confirmed that the exceptional performance could be mainly attributed to the promoted selective adsorption of 2,4-DCP for efficiently modulating holes by the strong coordination interactions between -Cl with lone-pair electrons in 2,4-DCP and Bi- with empty orbits on (010) facet-exposed BiVO₄ nanoflakes and to the coupled nano-SnO₂ for prolonging the charge lifetime of BiVO₄ by acting as the high-energy-level electron-accepting platform. This work provides a feasible strategy to develop excellent BiVO₄-based photoelectrochemical methods for efficiently controlling the conversion of chlorinated organics simultaneously with energy production and recovery.

Graphene-modulated assembly of zinc phthalocyanine on BiVO4 nanosheets for efficient visible-light catalytic conversion of CO2

Ultrathin zinc phthalocyanine/graphene/BiVO4 heterojunctions have been successfully synthesized for efficient wide visible-light catalytic conversion of CO2 to CO with 14-time photoactivity improvement compared to the bare BiVO4 nanosheet, attributed to the strengthened Z-scheme charge transfer and separation by increasing the optimized amount of highly dispersed ZnPc via the pre-modified graphene-modulated assembly.

In situ preparation of Bi2S3 nanoribbon-anchored BiVO4 nanoscroll heterostructures for the catalysis of Cr(vi) photoreduction

Novel Bi₂S₃ nanoribbon-anchored BiVO₄ nanoscroll heterostructures were fabricated, showing enhanced photocatalytic activity for Cr(vi) reduction under UV-visible light illumination.

2D elongated polyhedral-like YVO4 films: a novel photoanode for photoelectrochemical water splitting

YVO4 films, prepared on FTO substrates using a long-term hydrothermal method, possessing two-dimensional (2D) elongated polyhedral microcrystals and serving as a novel photoanode in the photoelectrochemical (PEC) field, are reported for the first time. The research indicates that YVO4 is a potential photoanode for PEC water splitting.

Oxygen-deficient WO3via high-temperature two-step annealing for enhanced and highly stable water splitting

In contrast with conventional one-step annealed WO₃, high-temperature two-step annealed WO₃ contains a higher concentration of oxygen deficiency, leading to more efficient charge separation and improved photocatalytic ability.