A direct Z-scheme oxygen vacant BWO/oxygen-enriched graphitic carbon nitride polymer heterojunction with enhanced photocatalytic activity

Guo

ACS Sustainable Chem. Eng.

et al. 2021

Exploring novel 2D heterojunction photocatalysts with a wide spectral response and high active site exposure has been a huge challenge. A small-sized catalyst with high dispersibility has been considered an ideal model for maximizing active sites and increasing atomic efficiency. Herein, the 0D/2D Z-scheme heterojunction was designed by in situ solvothermal and subsequent calcination in air by integrating dopant and defect doubly modified CeO2 nanodots and g-C3N4 nanosheets (CNNS). Ultrafine cobalt-doped CeO2 nanodots (≈4 to 5 nm) with enriched oxygen vacancies (Co-CeO2–OVs) were uniformly and tightly anchored on the surface of CNNS to form a heterojunction. The density functional theory (DFT) calculations confirmed that cobalt dopants and oxygen vacancies form impurity energy states at the top of a valence band, thus narrowing the band gap. The optimized 0D/2D heterojunction showed a remarkable hydrogen production rate of ∼203.6 μmol/h, which was approximately 4.9- and 30.8-fold higher than that of CNNS (∼41.2 μmol/h) and CeO2 (∼6.6 μmol/h), respectively. Moreover, a large quantum yield of ∼8.94% was achieved at 420 nm. The 0D/2D heterojunction with a larger intimate area provided abundant reactive active sites and strong electron interactions to excite photogenerated carrier dynamics, and the doping and defect engineering could expand the light response range by regulating the electronic band structure. Strong evidence provided by experimental results and DFT calculations proved the Z-scheme charge transfer pathway. This work not only provided a novel approach to integrate 0D nanodots and 2D nanosheets for the formation of intimate Z-scheme heterointerfaces but also deepened the understanding of the dopant–defect synergistic modification to optimize the band structure and electronic structures for high-efficient solar energy capture and conversion.

Section: Introductionmentioning

confidence: 99%

Dopant and Defect Doubly Modified CeO₂/g-C₃N₄ Nanosheets as 0D/2D Z-Scheme Heterojunctions for Photocatalytic Hydrogen Evolution: Experimental and Density Functional Theory Studies

Guo

ACS Sustainable Chem. Eng.

et al. 2021

Intl J of Energy Research

“…16,17,29 Based on the narrow bandgap, the formation of defect energy level also endows electrode materials' rapid electron transfer and significant performance. 34 The OVs concentration of MoO 3-x is further characterized using Raman spectra, as shown in Figure 3E. There are two main peaks located around 817 and 992 cm À1 corresponding to M═O stretch, which were further enlarged in Figure 3F.…”

Section: Resultsmentioning

confidence: 94%

Tunable oxygen deficient in MoO ₃ _‐x / MoO ₂ heterostructure for enhanced lithium storage properties

Feng

Liu

et al. 2021

MoO 3 is a kind of promising anode material for lithium-ion batteries (LIBs) owing to its high specific capacity and layered structure. However, the intrinsically sluggish redox kinetics results in poor rate and Li-ions storage capability. Oxygen vacancies (OVs) are considered to be effective in enhancing the conductivity and expanding the lattice distance of metal oxides. Here we report a strategy to synergize the merits of OVs and heterostructure by simply controlling the pH value of the reaction environment based on the reduction of ethanol. The tunable OVs concentration not only alters the bandgap but also expands the lattice spacing of MoO 3-x and eventually generates the MoO 3-x / MoO 2 heterojunction. The built-in electric field results from OVs and heterojunction drive high reaction kinetics, combing with the enlarged interlayer spacing, making MoO 3-x /MoO 2 heterojunction a promising electrode in Li-ion batteries. As expected, the MoO 3-x /MoO 2 heterojunction exhibits a high specific capacity of 600 mA g À1 at 0.1 A g À1 and 400 mAh g À1 at 1 A g À1 with a high capacity retention of 61%. This strategy on oxygen vacancies paves the way to regulate the valence structure, lattice structure and even component of electrode materials, endows them desired features, and provides an alternative way to meet the demands in energy storage systems.

“…This 3D Z-scheme heterojunction built an electric field that accelerates the interfacial charge transfer. Under light irradiation, electrons are excited from Bi 4p orbital to Bi 6p orbital and form an electric field that reduce recombination rate of charge carriers [31]. Bi 2 WO 6 has been grown vertically on Ta 3 N 5 nanofibers to prepare visible light active Bi 2 WO 6 /Ta 3 N 5 Z-scheme heterojunction photocatalyst.…”

Section: Layered Structured Perovskitesmentioning

confidence: 99%

Perovskite Based Photocatalyst for Wastewater Treatment: Green Approach of Environmental Sustainability

Das¹,

Mahata²,

Adak³

2021

AJBES

Persistent organic substances in wastewater are creating serious problems to the living world as well as to the environment, thereby creating huge detrimental impact on the ecosystem. In view of the grave situation, removal of the persistent organic substances from wastewater effluent holds a great promise to balance the ecosystem and to sustain societal impact value. In this respect, perovskite based photocatalysts have achieved remarkable attention to the scientific community due to their unique structural features and flexibility of composition. Again, surface polarization and electric dipole-dipole interaction in the perovskite material make them attractive for photocatalytic application. This review paper summarized the photocatalytic activity of perovskite materials and their modification to enhance catalytic activity for wastewater treatment. The modification in perovskite has been done to reduce bandgap energy for enhanced visible light activity, separation of charge carriers for their long lifetime, and fast photocatalytic reaction. The recent investigation of ABO 3 type perovskite, layered perovskite, and halide type of perovskite photocatalysts have been discussed detailly. The modification of corresponding perovskites by doped and formation of heterojunction is investigated carefully. The formation and identification of reactive oxygen species (ROS) and their degradation mechanism by trapping experiment and ESR technique has been summarized here. Finally, large scale with energy and environmental related research should be processed for a permanent solution of wastewater problem.