Search

Vanadium oxides have been regarded as highly promising cathodes for aqueous zinc-ion batteries (ZIBs). However, obtaining high-performance vanadium oxide-based cathodes suitable for industrial application remains a significant challenge due to the need for cost-effective, straightforward, and efficient preparation methods. Herein, we present a facile and rapid synthesis of a composite cathode, consisting of layer-stacked VO 2 /V 2 O 5 and graphene-like carbon nanosheets, in just 2.5 s by treating the commercial V 2 O 5 powder via a flash Joule heating strategy. When employed as the cathode for ZIBs, the resulting composite delivers a comparable rate capacity of 459 mA h g -1 at 0.2 A g -1 and remarkable cycle stabilities of 355.5 mA h g -1 after 2500 cycles at 1.0 A g -1 and 169.5 mA h g -1 after 10,000 cycles at 10 A g -1 , respectively. Further electrochemical analysis reveals that the impressive performance is attributed to the accelerated charge transfer and the alleviated structure degradation, facilitated by the abundant sites and a built-in electric field of the layer-stacked VO 2 /V 2 O 5 heterostructure, as well as the excellent conductivity of graphene-like carbon nanosheets. This work introduces a unique approach for ultrafast and low-cost fabrication of high-performance vanadium oxide-based composite cathodes toward efficient ZIBs.

Integrating hematite nanostructures with efficient layer double hydroxides (LDHs) is highly desirable to improve the photoelectrochemical (PEC) water oxidation performance. Here, an innovative and facile strategy is developed to fabricate the FeTi-LDH overlayer decorated Fe 2 O 3 /Fe 2 TiO 5 photoanode via a surface self-transformation induced by the co-treatment of hydrazine and NaOH at room temperature. Electrochemical measurements find that this favorable structure can not only facilitate the charge transfer/separation at the electrode/electrolyte interface but also accelerate the surface water oxidation kinetics. Consequently, the as-obtained Fe 2 O 3 /Fe 2 TiO 5 /LDH photoanode exhibits a remarkably increased photocurrent density of 3.54 mA cm -2 at 1.23 V versus reversible hydrogen electrode (RHE) accompanied by an obvious cathodic shift (≈140 mV) in the onset potential. This work opens up a new and effective pathway for the design of high-performance hematite photoanodes toward efficient PEC water oxidation., (© 2023 Wiley-VCH GmbH.)

Hematite has been considered as a promising photoanode candidate for photoelectrochemical (PEC) water oxidation and has attracted numerous interests in the past decades. However, intrinsic drawbacks drastically lower its photocatalytic activity. Ti-based modifications including Ti-doping, Fe 2 O 3 /Fe 2 TiO 5 heterostructures, TiO 2 passivation layers, and Ti-containing underlayers have shown great potential in enhancing the PEC conversion efficiency of hematite. Moreover, the combination of Ti-based modifications with various strategies towards more efficient hematite photoanodes has been widely investigated. Nevertheless, a corresponding comprehensive overview, especially with the most recent working mechanisms, is still lacking, limiting further improvement. In this respect, by summarizing the recent progress in Ti-modified hematite photoanodes, this review aims to demonstrate how the integration of titanium and iron atoms into hematite influences the PEC properties by tuning the carrier behaviours. It will provide more cues for the rational design of high-performance hematite photoanodes towards future practical applications.

Surface electron-hole recombination and low conductivity have significantly hindered the photoelectrochemical water oxidation performance of hematite. Here we report a surface N and Sn co-incorporation in hematite for efficient water oxidation, which shows a greatly enhanced photocurrent density of 2.30 mA/cm 2 at 1.23 V vs. RHE when compared to the pristine hematite (0.89 mA/cm 2 ). Moreover, after the subsequent loading of Co-Pi cocatalyst, a further improved photocurrent density of 2.80 mA/cm 2 at 1.23 V vs. RHE can also be achieved. The excellent performance can be attributed to the synergistic effect of N and Sn in hematite, in which the surface Sn-doping could increase the donor density of hematite while the N-incorporation could adjust the amount of Sn in hematite to suppress the surface charge recombination and further increase the donor density. To the best of our knowledge, it should be the first report to reveal the synergistic effect of non-metal element N and metallic element Sn in hematite for high performance, which could be a feasible way towards the development of efficient hematite photoanodes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Here, we successfully synthesized the oxygen-linked band and porous defect co-modified orange carbon nitride (AF-C 3 N 4 ) using a simple method. Further, the band structure calculation of its simulated structure is performed by DFT, which shows that the introduction of oxygen-linked band can adjust its band structure. The photocatalytic degradation rates of 0.3AF-C 3 N 4 for bisphenol A and 2-mercaptobenzothiazole were 8 times and 2.73 times that of the original g-C 3 N 4 , respectively. Moreover, 0.3AF-C 3 N 4 also shows photocatalytic activity under different wavelength light (blue, green and red light), which indicates that the synthesized materials have a broad spectrum of photocatalytic activity. Further, we proposed a possible photocatalytic degradation pathway by HPLC-MS analysis. Free radical quenching test and ESR spectra show that the generated superoxide radicals (•O 2 - ), hydroxyl radicals (•OH) and holes (h + ) cause photodegradation, while enhancing singlet oxygen ( 1 O 2 ) and weaken the content of hydrogen peroxide has further proved that active oxygen groups play an important role in the photocatalytic degradation process. Additionally, the 0.3AF-C 3 N 4 can also be a photoelectrochemical sensor to detect the concentration of bisphenol A (λ ≥ 550 nm). This study provides a new strategy for the synthesis of orange carbon nitride by oxygen-linked band and porous defect co-modification for photocatalytic applications., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Graphene quantum dots modified Bi 2 WO 6 (GQD/Bi 2 WO 6 ) composites is applied to photocatalytic N 2 fixation. The as-prepared GQD/Bi 2 WO 6 samples showed considerable increase in photocatalytic nitrogen fixation compared to the pure Bi 2 WO 6 and GQD. The results revealed that GQD uniformly placed on the surface of Bi 2 WO 6 and tight junction between the two samples helped to boost the photocatalytic activity. The PL, photocurrent and EIS analyses further demonstrated that the composite had the low recombination rate of photo-generated charges. Photocatalytic nitrogen fixation test indicated that GQD/Bi 2 WO 6 with 10 wt% GQDs exhibited the highest ammonia synthesis rate in the presence of visible light, which is 8.88-fold and 33.8-fold higher than pure Bi 2 WO 6 and GQD. Simultaneously, the GQD/Bi 2 WO 6 sample has high stability., (Copyright © 2019. Published by Elsevier Inc.)

An effective cocatalyst is usually required to improve the performance of photoelectrochemical (PEC) water splitting catalysts. A fluorine-doped FeOOH (F:FeOOH) cocatalyst on a hematite photoanode was used to lower the onset potential by 140 mV and significantly improve the PEC performance. Moreover, a more effective dual cocatalytic system was prepared by subsequent loading of a FeNiOOH cocatalyst, which resulted in a further decrease of the onset potential by 270 mV. The final onset potential of the Fe 2 O 3 /F:FeOOH/FeNiOOH photoanode was lowered to 0.45 V versus the reversible hydrogen electrode (RHE), which is one of the lowest onset potential values ever reported for hematite photoanodes. The photocurrent also dramatically increased by a factor of approximately 3 to 0.9 mA cm -2 at 1.0 V versus RHE. Based on the structural, chemical, and electrochemical impedance spectroscopy characterization, the enhanced performance was attributed to the F:FeOOH overlayer, which reduced the surface recombination and accelerated the oxygen evolution reaction activity, and the FeNiOOH cocatalyst, which further enhanced the reaction kinetics. The facile preparation of the F:FeOOH cocatalyst and the design of the dual cocatalytic system will allow the development of high-performance hematite photoanodes., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A FeNiOOH-decorated hematite photoanode has been prepared using a facile electrodeposition method, with a significant cathodic shift of the onset potential (up to 190 mV) compared to the pristine sample. Synchrotron radiation based techniques have been used to identify the composition of the catalyst indicating the presence of FeOOH and NiOOH (FeNiOOH). The enhanced performance can be attributed to the better oxidation evolution reaction kinetics with the FeNiOOH cocatalyst. The FeNiOOH-decorated hematite is very stable for a long time. Moreover, the cocatalyst can be well coupled to the Pt-modified hematite photoanode achieving a high photocurrent of 2.21 mA cm(-2) at 1.23 V vs. RHE. The good catalytic properties and the facile preparation method suggest that the decoration of FeNiOOH is a favorable strategy to improve the performance of hematite.

A thin Fe2TiO5 layer was produced on hematite either by evaporating a TiCl4 solution on FeOOH or by a simple HF-assisted Ti treatment of FeOOH, both followed by annealing. The prepared Fe2TiO5-hematite heterostructure showed a significant enhancement in photocurrent density compared to that of the pristine hematite. For example, the sample after HF-assisted Ti treatment exhibited a significantly enhanced photocurrent of 2.0 mA/cm(2) at 1.23 V vs RHE. Moreover, the performance of the Fe2TiO5-hematite heterostructure can be further improved by coupling with Co-Pi catalysts, achieving a higher photocurrent of 2.6 mA/cm(2) at 1.23 V vs RHE. Synchrotron-based soft X-ray absorption spectroscopy analyses clearly revealed the existence of an Fe2TiO5 structure on hematite forming a heterojunction, which reduced the photogenerated hole accumulation and then improved the performance.

The coating of nanoscaled carboxylated carbonaceous fragments on carbon nanotubes (CNTs) has been directly observed in chemical imaging with a concurrent identification of their electronic structure by scanning transmission X-ray microscopy. The coating also shields the detection of the CNT/nanoparticle interaction.