Interface Engineering of a CoOx/Ta3N5Photocatalyst for Unprecedented Water Oxidation Performance under Visible-Light-Irradiation

Achievement of visible-light-driven Z-scheme overall water splitting using barium-modified Ta3N5 as a H2-evolving photocatalyst

Barium-modified Ta₃N₅ for the promotion of proton reduction is first employed as a H₂-evolving photocatalyst for visible-light-driven Z-scheme overall water splitting.

Ta₃N₅ is one of the most promising photocatalyst candidates for solar water splitting, but it still remains challenging to achieve overall water splitting via Ta₃N₅-based photocatalysts regardless of whether it uses a one step or two step method. Here we will address the relatively poor photocatalytic proton reduction of Ta₃N₅ with an effort for the promotion of charge separation via barium modification. One-pot nitridation of barium nitrate-impregnated Ta₂O₅ precursor was adopted here for the synthesis of Ta₃N₅ accompanied with the creation of a Ta₃N₅/BaTaO₂N heterostructure and surface passivation. Due to the synergetic effect of the improved interfacial charge separation and the decreased defect density, the photocatalytic H₂ evolution rate of barium-modified Ta₃N₅ is effectively promoted. Encouraged by this, a visible-light-driven Z-scheme overall water splitting system was successfully constructed by using the barium-modified Ta₃N₅ as a H₂-evolving photocatalyst, together with a PtO_x/WO₃ and IO₃^–/I^– pair as an O₂-evolving photocatalyst and a redox mediator, respectively.

Photocatalyzed Hydrogen Evolution from Water by a Composite Catalyst of NH2 -MIL-125(Ti) and Surface Nickel(II) Species

A composite of the metal-organic framework (MOF) NH₂ -MIL-125(Ti) and molecular and ionic nickel(II) species, catalyzed hydrogen evolution from water under UV light. In 95 v/v % aqueous conditions the composite produced hydrogen in quantities two orders of magnitude higher than that of the virgin framework and an order of magnitude greater than that of the molecular catalyst. In a 2 v/v % water and acetonitrile mixture, the composite demonstrated a TOF of 28 mol H₂  g(Ni)^-1  h^-1 and remained active for up to 50 h, sustaining catalysis for three times longer and yielding 20-fold the amount of hydrogen. Appraisal of physical mixtures of the MOF and each of the nickel species under identical photocatalytic conditions suggest that similar surface localized light sensitization and proton reduction processes operate in the composite catalyst. Both nickel species contribute to catalytic conversion, although different activation behaviors are observed.

Insight into the charge transfer in particulate Ta3N5 photoanode with high photoelectrochemical performance

Charge separation is one of the most critical factors for generating solar fuels via photoelectrochemical water splitting, but it is still not well understood. This work reveals the fundamental role of charge transfer in photoanodes for achieving high charge separation efficiency. Specifically, we fabricated a particulate Ta3N5 photoanode by a bottom-up method. By improving the charge separation with refined necking treatment, the photocurrent is increased by two orders of magnitude. The charge separation efficiency (ηsep) is analyzed by dividing it into charge generation efficiency (Φgene) and transportation efficiency (Φtrans). Necking treatment is found to substantially improve the electron transfer. Transient photovoltage (TPV) measurements based on the Dember effect is used to confirm the benefit of necking treatment in improving the charge transportation. The superior electron transfer in the necked-Ta3N5 electrode is further evidenced by the facile electron exchange reaction with the ferri/ferrocyanide redox couple. Moreover, cobalt phosphate is found to promote both charge separation and surface reaction, resulting in a photocurrent of 6.1 mA cm-2 at 1.23 V vs. RHE, which is the highest response for a particulate photoanode.

Role of Oxygen Defects on the Photocatalytic Properties of Mg-Doped Mesoporous Ta3 N5

Tantalum nitride (Ta3 N5 ) highlights an intriguing paradigm for converting solar energy into chemical fuels. However, its photocatalytic properties are strongly governed by various intrinsic/extrinsic defects. In this work, we successfully prepared a series of Mg-doped mesoporous Ta3 N5 using a simple method. The photocatalytic and photoelectrochemical properties were investigated from the viewpoint of how defects such as accumulation of oxygen and nitrogen vacancies contribute to the catalytic activity. Our findings suggest that Mg doping is accompanied by an accumulation of oxygen species and a simultaneous elimination of nitrogen vacancies in Ta3 N5 . These oxygen species in Ta3 N5 induce delocalized shallow donor states near the conduction band minimum and are responsible for high electron mobility. The superior photocatalytic activity of Mg-doped Ta3 N5 can then be understood by the improved electron-hole separation as well as the lack of nitrogen vacancies, which often serve as charge-recombination centers.

Strongly Enhanced Water Splitting Performance of Ta3 N5 Nanotube Photoanodes with Subnitrides

Subnitrides strongly enhance the efficiency of Ta3 N5 -nanotube photoanodes in photochemical water splitting. The fabrication of Ta3 N5 nanotube layers with a controlled subnitride layer at the interface to the back contact is demonstrated. The insertion of this subnitride layer has a strong influence on the electron transfer to the back contact, and as a result leads to a drastic shift in photocurrent onset potential and a considerable enhancement of photocurrent conversion efficiency.

Theoretical study on the surface stabilities, electronic structures and water adsorption behavior of the Ta3N5(110) surface

DFT calculations were performed to study the surface stabilities, electronic structures and water adsorption behavior of the Ta₃N₅(100) surface.

Visible light-induced photochemical oxygen evolution from water by 3,4,9,10-perylenetetracarboxylic dianhydride nanorods as an n-type organic semiconductor

The designed nanorods with cobalt oxide achieve an AQE of 4.6 ± 0.3% for oxygen evolution under visible light irradiation at 410 nm.

Surface and interface design in cocatalysts for photocatalytic water splitting and CO2reduction

This review outlines the recent progress on designing the surface and interface of cocatalysts to create highly efficient photocatalysts for water splitting and CO₂reduction.

Anatase Mg0.05Ta0.95O1.15N0.85: a novel photocatalyst for solar hydrogen production

Anatase Mg_0.05Ta_0.95O_1.15N_0.85, exhibiting a narrow band gap for solar hydrogen, is a promising visible-light-response photocatalyst for photocatalytic or photoelectrochemical water splitting.

Microwave-assisted fabrication of porous hematite photoanodes for efficient solar water splitting

Efficient PEC water splitting has been achieved over porous hematite photoanodes with wormlike networks.

An Iron-based Film for Highly Efficient Electrocatalytic Oxygen Evolution from Neutral Aqueous Solution

An ultrathin Fe-based film was prepared by electrodeposition from an Fe(II) solution through a fast and simple cyclic voltammetry method. The extremely low Fe loading of 12.3 nmol cm(-2) on indium tin oxide electrodes is crucial for high atom efficiency and transparence of the resulted film. This Fe-based film was shown to be a very efficient electrocatalyst for oxygen evolution from neutral aqueous solution with remarkable activity and stability. In a 34 h controlled potential electrolysis at 1.45 V (vs NHE) and pH 7.0, impressive turnover number of 5.2 × 10(4) and turnover frequency of 1528 h(-1) were obtained. To the best of our knowledge, these values represent one of the highest among electrodeposited catalyst films for water oxidation under comparable conditions. The morphology and the composition of the catalyst film was determined by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray, and X-ray photoelectron spectroscopy, which all confirmed the deposition of Fe-based materials with Fe(III) oxidation state on the electrode. This study is significant because of the use of iron, the fast and simple cyclic voltammetry electrodeposition, the extremely low catalyst loading and thus the transparency of the catalyst film, the remarkable activity and stability, and the oxygen evolution in neutral aqueous media.

Facile fabrication of InSe nanosheets: towards efficient visible-light-driven H2 production by coupling with P25

InSe nanosheets and their coupling with P25 have been successfully synthesized via a hydrothermal–calcining process, and they were for the first time used for visible light photocatalytic H₂ production.