2D/2D Heterojunction of Ultrathin MXene/Bi2WO6 Nanosheets for Improved Photocatalytic CO2 Reduction

Electrocatalytic oxygen evolution reaction (OER) is a core reaction responsible for converting renewable electricity into storable fuels; yet, it is kinetically challenging, because of the complex ...

Fe-Based Electrocatalysts for Oxygen Evolution Reaction: Progress and Perspectives

A A novel three-dimensional microspheres mediator-free Z-scheme Ag3VO4/BiVO4 heterojunction photocatalyst was successfully obtained for the first time. The photocatalytic performance of the as-prepared photocatalyst was systematically examined via the photocatalytic reduction of Cr6+ and oxidation of Bisphenol S under visible-light irradiation. Among these samples, 0.24-Ag3VO4/BiVO4 exhibits the highest photocatalytic performances, the photocatalytic reduction and oxidation efficiency of 74.9 and 94.8%, respectively, can be achieved. The enhanced photocatalytic performance is attributed to the build-in electric field assisted charge transfer between the Ag3VO4 and BiVO4, and the increasing lifetime of the charge carrier confirmed by the results of time-resolved fluorescence spectra and photoelectrochemical measures. Moreover, based on the results of free radical scavenging activity test, and EPR experiments, it has been verified that the Ag3VO4/BiVO4 heterostructures follow a typical Z-scheme charge transfer mechanism rather than conventional type-II heterojunction charge transfer mechanism. Furthermore, the theoretical understanding of the underlying mechanism was also supported, while the energy band structure, and Fermi level were systematically calculated using the density functional theory approach. The results show that a built-in electric field directed from Ag3VO4 to BiVO4 surface was established as an equalized Fermi level was reached, which benefits the separation of photogenerated charge carriers in the way of a Z-scheme charge transfer mechanism. The strategy to form the three-dimensional microspheres Z-scheme heterojunction photocatalyst may offer new insight into the Z-scheme charge transfer mechanism for applications in the field of solar energy conversion.

A novel Z-scheme Ag3VO4/BiVO4 heterojunction photocatalyst: study on the excellent photocatalytic performance and photocatalytic mechanism

Peroxymonosulfate activation for efficient sulfamethoxazole degradation by Fe3O4/β-FeOOH nanocomposites: Coexistence of radical and non-radical reactions

Owing to the sluggish kinetics for water oxidation, severe surface charge recombination is a major energy loss that hinders efficient photoelectrochemical (PEC) water splitting. Herein, a simple process is developed for preparing a new type of low‐cost iron‐cobalt oxide (FeCoOx) as an efficient co‐catalyst to suppress the surface charge recombination on bismuth vanadate (BiVO4) photoanodes. The new FeCoOx/BiVO4 photoanode exhibits a high photocurrent density of 4.82 mA cm−2 at 1.23 V versus the reversible hydrogen electrode under AM 1.5 G illumination, which corresponds to >100% increase compared to that of the pristine BiVO4 photoanode. The photoanode also demonstrates a high charge separation efficiency of ≈90% with excellent stability of over 10 h, indicating the excellent catalytic performance of FeCoOx in the PEC process. Density functional theory calculations and experimental studies reveal that the incorporation of Fe into CoOx generates abundant oxygen vacancies and forms a p‐n heterojunction with BiVO4, which effectively promotes the hole transport/trapping from the BiVO4 photocatalyst and reduces the overpotential for oxygen evolution reaction (OER), resulting in remarkably increased photocurrent densities and durability. This work demonstrates a feasible process for depositing cheap FeCoOx as an excellent OER cocatalyst on photoanodes for PEC water splitting.

New iron-cobalt oxide catalysts promoting BIVO4 films for photoelectrochemical water splitting

Photoelectrochemical (PEC) water splitting is a promising method for storing solar energy in the form of hydrogen fuel, but it is greatly hindered by the sluggish kinetics of the oxygen evolution reaction (OER). Herein, a facile solution impregnation method is developed for growing ultrathin (2 nm) highly crystalline β-FeOOH nanolayers with abundant oxygen vacancies on BiVO4 photoanodes. These exhibited a remarkable photocurrent density of 4.3 mA cm-2 at 1.23 V (vs. reversible hydrogen electrode (RHE), AM 1.5 G), which is approximately two times higher than that of amorphous FeOOH fabricated by electrodeposition. Systematic studies reveal that the excellent PEC activity should be attributed to their ultrathin crystalline structure and abundant oxygen vacancies, which could effectively facilitate the hole transport/trapping and provide more active sites for water oxidation.

Ultrathin FeOOH Nanolayers with Abundant Oxygen Vacancies on BiVO4 Photoanodes for Efficient Water Oxidation

The leaf-like structure BiVO4 electrode and MFe2O4/BiVO4 (M = Ni, Co) composite photoelectrodes were prepared by electrochemical deposition, ensuing heating treatment and electrophoretic deposition technology The characterizations of SEM, XRD and DRS indicated that the BiVO4 derivatives mainly existed in small nanoparticles with monoclinic phase and exhibited stronger light absorption capability than that of pure BiVO4 Hereon, the respective photoelectrochemical (PEC) activities of BiVO4 and its derived composites were systematically studied The results suggested that the NiFe2O4/BiVO4 and CoFe2O4/BiVO4 not only showed higher photocurrent response values at 123 V vs NHE than pure BiVO4 electrode under visible light illumination, but also played a superior PEC hydrogen evolution performance, which was considered owing to their strong absorption to light, reduction combination of carriers and effective separation of electrons and holes

Synthesis of MFe2O4 (M = Ni, Co)/BiVO4 film for photolectrochemical hydrogen production activity

Oxygen vacancy (Vo) on transition metal oxides plays a crucial role in determining their chemical/physical properties. Conversely, the capability to directly detect the changing process of oxygen vacancies (Vos) will be important to realize their full potentials in the related fields. Herein, with a novel synchronous illumination X-ray photoelectron spectroscopy (SI-XPS) technique, we found that the surface Vos (surf-Vos) exhibit a strong selectivity for binding with the water molecules, and sequentially capture an oxygen atom to achieve the anisotropic self-healing of surface lattice oxygen. After this self-healing process, the survived subsurface Vos (sub-Vos) promote the charge excitation from Ti to O atoms due to the enriched electron located on low-coordinated Ti sites. However, the excessive sub-Vos would block the charge separation and transfer to TiO2 surfaces resulted from the destroyed atomic structures. These findings open a new pathway to explore the dynamic changes of Vos and their roles on catalytic properties, not only in metal oxides, but in crystalline materials more generally.

Direct Observation of Oxygen Vacancy Self-Healing on TiO 2 Photocatalysts for Solar Water Splitting

Understanding the origin of formation and active sites of oxygen evolution reaction (OER) cocatalysts is highly required for solar photoelectrochemical (PEC) devices that generate hydrogen efficiently from water. Herein, we employed a simple pH-modulated method for in situ growth of FeNi oxyhydroxide ultrathin layers on BiVO4 photoanodes, resulting in one of the highest currently known PEC activities of 5.8 mA cm-2 (1.23 VRHE , AM 1.5 G) accompanied with an excellent stability. More importantly, both comparative experiments and density functional theory (DFT) studies clearly reveal that the selective formation of Bi-O-Fe interfacial bonds mainly contributes the enhanced OER activities, while the construction of V-O-Ni interfacial bonds effectively restrains the dissolution of V5+ ions and promotes the OER stability. Thereby, the synergy between iron and nickel of FeNi oxyhydroxides significantly improved the PEC water oxidation properties of BiVO4 photoanodes.

Yingpu Bi

Papers

Ultrathin FeOOH Nanolayers with Abundant Oxygen Vacancies on BiVO4 Photoanodes for Efficient Water Oxidation

Synthesis of MFe2O4 (M = Ni, Co)/BiVO4 film for photolectrochemical hydrogen production activity

Direct Observation of Oxygen Vacancy Self-Healing on TiO 2 Photocatalysts for Solar Water Splitting

Unveiling the Activity and Stability Origin of BiVO4 Photoanodes with FeNi Oxyhydroxides for Oxygen Evolution

Designing non-noble/semiconductor Bi/BiVO4 photoelectrode for the enhanced photoelectrochemical performance