Artificial photosynthesis on tree trunk derived alkaline tantalates with hierarchical anatomy: towards CO2 photo-fixation into CO and CH4

Research Progress on Photocatalytic CO2 Reduction Based on Perovskite Oxides

Photocatalytic CO2 reduction to valuable fuels is a promising way to alleviate anthropogenic CO2 emissions and energy crises. Perovskite oxides have attracted widespread attention as photocatalysts for CO2 reduction by virtue of their high catalytic activity, compositional flexibility, bandgap adjustability, and good stability. In this review, the basic theory of photocatalysis and the mechanism of CO2 reduction over perovskite oxide are first introduced. Then, perovskite oxides' structures, properties, and preparations are presented. In detail, the research progress on perovskite oxides for photocatalytic CO2 reduction is discussed from five aspects: as a photocatalyst in its own right, metal cation doping at A and B sites of perovskite oxides, anion doping at O sites of perovskite oxides and oxygen vacancies, loading cocatalyst on perovskite oxides, and constructing heterojunction with other semiconductors. Finally, the development prospects of perovskite oxides for photocatalytic CO2 reduction are put forward. This article should serve as a useful guide for creating perovskite oxide-based photocatalysts that are more effective and reasonable.

Recent Advances in the Synthesis and Application of Three-Dimensional Graphene-Based Aerogels

Three-dimensional graphene-based aerogels (3D GAs), combining the intrinsic properties of graphene and 3D porous structure, have attracted increasing research interest in varied fields with potential application. Some related reviews focusing on applications in photoredox catalysis, biomedicine, energy storage, supercapacitor or other single aspect have provided valuable insights into the current status of Gas. However, systematic reviews concentrating on the diverse applications of 3D GAs are still scarce. Herein, we intend to afford a comprehensive summary to the recent progress in the preparation method (template-free and template-directed method) summarized in Preparation Strategies and the application fields (absorbent, anode material, mechanical device, fire-warning material and catalyst) illustrated in Application of 3D GAs with varied morphologies, structures, and properties. Meanwhile, some unsettled issues, existing challenges, and potential opportunities have also been proposed in Future Perspectives to spur further research interest into synthesizing finer 3D GAs and exploring wider and closer practical applications.

One-step aerosol synthesis of a double perovskite oxide (KBaTeBiO6) as a potential catalyst for CO2 photoreduction

This study presents a comprehensive investigation on the aerosol synthesis of a semiconducting double perovskite oxide with a nominal composition of KBaTeBiO6, which is considered as a potential candidate for CO2 photoreduction. We demonstrate the rapid synthesis of the multispecies compound KBaTeBiO6 with extremely high purity and controllable size through a single-step furnace aerosol reactor (FuAR) process. The formation mechanism of the perovskite through the aerosol route is investigated using thermogravimetric analysis to identify the optimal reference temperature, residence time and other operational parameters in the FuAR synthesis process to obtain highly pure KBaTeBiO6 nanoparticles. It is observed that particle formation in the FuAR is based on a combination of gas-to-particle and liquid-to-particle mechanisms. The phase purity of the perovskite nanoparticles depends on the ratio of the residence time and the reaction time. The particle size is strongly affected by the precursor concentration, residence time and furnace temperature. Finally, the photocatalytic performance of the synthesized KBaTeBiO6 nanoparticles is investigated for CO2 photoreduction under UV-light. The best performing sample exhibits an average CO production rate of 180 μmol g-1 h-1 in the first half hour with a quantum efficiency of 1.19%, demonstrating KBaTeBiO6 as a promising photocatalyst for CO2 photoreduction.

Enhanced photocatalytic CO2 reduction by constructing an In2O3–CuO heterojunction with CuO as a cocatalyst

Under the excitation of light on the photocatalyst, artificial photosynthesis can effectively realize the conversion of CO₂ into chemical raw materials or fuels.

Hierarchically structured porous materials: synthesis strategies and applications in energy storage

To address the growing energy demands of sustainable development, it is crucial to develop new materials that can improve the efficiency of energy storage systems. Hierarchically structured porous materials have shown their great potential for energy storage applications owing to their large accessible space, high surface area, low density, excellent accommodation capability with volume and thermal variation, variable chemical compositions and well controlled and interconnected hierarchical porosity at different length scales. Porous hierarchy benefits electron and ion transport, and mass diffusion and exchange. The electrochemical behavior of hierarchically structured porous materials varies with different pore parameters. Understanding their relationship can lead to the defined and accurate design of highly efficient hierarchically structured porous materials to enhance further their energy storage performance. In this review, we take the characteristic parameters of the hierarchical pores as the survey object to summarize the recent progress on hierarchically structured porous materials for energy storage. This is the first of this kind exclusively to survey the performance of hierarchically structured porous materials from different porous characteristics. For those who are not familiar with hierarchically structured porous materials, a series of very significant synthesis strategies of hierarchically structured porous materials are firstly and briefly reviewed. This will be beneficial for those who want to quickly obtain useful reference information about the synthesis strategies of new hierarchically structured porous materials to improve their performance in energy storage. The effect of different organizational, structural and geometric parameters of porous hierarchy on their electrochemical behavior is then deeply discussed. We outline the existing problems and development challenges of hierarchically structured porous materials that need to be addressed in renewable energy applications. We hope that this review can stimulate strong intuition into the design and application of new hierarchically structured porous materials in energy storage and other fields.

3D structured materials and devices for artificial photosynthesis

Artificial photosynthesis is an effective way to convert solar energy into fuels, which is of great significance to energy production and reduction of atmospheric CO₂ content. In recent years, 3D structured artificial photosynthetic system has made great progress as an effective design strategy. This review first highlights several typical mechanisms for improved artificial photosynthesis with 3D structures: improved light harvesting, mass transfer and charge separation. Then, we summarize typical examples of 3D structured artificial photosynthetic systems, including bioinspired structures, photonic crystals (PC), designed photonic structures (PC coupling structure, plasmon resonance structure, optical resonance structure, metamaterials), 3D-printed systems, nanowire integrated systems and hierarchical 3D structures. Finally, we discuss the problems and challenges to the application and development of 3D artificial photosynthetic system and the possible trends of future development. We hope this review can inspire more progress in the field of artificial photosynthesis.

Intriguingly high thermal conductivity increment for CuO nanowires contained nanofluids with low viscosity

Nanofluids offer the exciting new possibilities to enhance heat transfer performance. In this paper, experimental and theoretical investigations have been conducted to determine the effect of CuO nanowires on the thermal conductivity and viscosity of dimethicone based nanofluids. The CuO nanowires were prepared through a thermal oxidation method, and the analysis indicated that the as-prepared CuO nanowires had high purity, monocrystalline with a monoclinic structure and large aspect ratio compared to CuO nanospheres. The experimental data show that the thermal conductivity of the nanofluids increases with the volume fraction of CuO nanowires or nanospheres, with a nearly linear relationship. For the nanofluid with the addition of 0.75 vol.% CuO nanowires, the thermal conductivity enhancement is up to 60.78%, which is much higher than that with spherical CuO nanoparticles. The nanofluids exhibit typical Newtonian behavior, and the measured viscosity of CuO nanowires contained nanofluids were found only 6.41% increment at the volume fraction of 0.75%. It is attractive in enhanced heat transfer for application. The thermal conductivity and viscosity of CuO nanofluids were further calculated and discussed by comparing our experimental results with the classic theoretical models. The mechanisms of thermal conductivity and viscosity about nanofluids were also discussed in detail.

A review on photocatalytic CO2 reduction using perovskite oxide nanomaterials

As the search for efficient catalysts for CO₂ photoreduction continues, nanostructured perovskite oxides have emerged as a class of high-performance photocatalytic materials. The perovskite oxide candidates for CO₂ photoreduction are primarily nanostructured forms of titanates, niobates, tantalates and cobaltates. These materials form the focus of this review article because they are much sought-after due to their nontoxic nature, adequate chemical stability, and tunable crystal structures, bandgaps and surface energies. As compared to conventional semiconductors and nanomaterial catalysts, nanostructured perovskite oxides also exhibit an extended optical-absorption edge, longer charge carrier lifetimes, and favorable band-alignment with respect to reduction potential of activated CO₂ and reduction products of the same. While CO₂ reduction product yields of several hundred μmol^-1 h^-1 are observed with many types of perovskite oxide nanomaterials in stand-alone forms, yield of such quantities are not common with semiconductor nanomaterials of other types. In this review, we present current state-of-the-art synthesis methods to form perovskite oxide nanomaterials, and procedures to engineer their bandgaps. This review also presents a comprehensive summary and discussion on crystal structures, defect distribution, morphologies and electronic properties of the perovskite oxides, and correlation of these properties to CO₂ photoreduction performance. This review offers researchers key insights for developing advanced perovskite oxides in order to further improve the yields of CO₂ reduction products.

Electrocatalytic CO2 Reduction to Formate at Low Overpotentials on Electrodeposited Pd Films: Stabilized Performance by Suppression of CO Formation

Palladium nanoparticles are effective for catalytic CO₂ reduction. However, CO, one of the most important products in the CO₂ reduction sequence, has strong affinity for the Pd surface and poisons the catalytic sites rapidly. In this research, an electrodeposited Pd film exhibits high activity for CO₂ reduction to formate with the suppression of CO formation at low overpotentials. The substrates, electrodeposition process and the post-treatment of the Pd films affect the CO₂ reduction pathway significantly. The cyclic voltammetry deposition produces films that exhibit more porous morphologies and have higher current efficiencies for formate than those of films produced at constant potential. These films show stable CO₂ reduction performance at low overpotentials and have high current efficiencies (≈50-60 % depending on the substrate) for formate formation at a potential of -0.4 V versus the reversible hydrogen electrode without any detectable CO formation. It seems that the Pd surface generated by the new electrodeposition process described here produces a nanostructure that can promote formate formation and suppress CO formation.

CO2 reduction over NaNbO3 and NaTaO3 perovskite photocatalysts

Both NaNbO₃ and NaTaO₃ exhibit interesting intrinsic photocatalytic activities for CO₂ reduction in terms of conversion and selectivity.

Hierarchically porous materials: synthesis strategies and structure design

This review addresses recent advances in synthesis strategies of hierarchically porous materials and their structural design from micro-, meso- to macro-length scale.

Hierarchical photocatalysts

The design, fabrication, performance and applications of hierarchical semiconductor photocatalysts are thoroughly reviewed and apprised.

Three-Dimensional Porous Aerogel Constructed by g-C3N4 and Graphene Oxide Nanosheets with Excellent Visible-Light Photocatalytic Performance

It is curial to develop a high-efficient, low-cost visible-light responsive photocatalyst for the application in solar energy conversion and environment remediation. Here, a three-dimensional (3D) porous g-C3N4/graphene oxide aerogel (CNGA) has been prepared by the hydrothermal coassembly of two-dimensional g-C3N4 and graphene oxide (GO) nanosheets, in which g-C3N4 acts as an efficient photocatalyst, and GO supports the 3D framework and promotes the electron transfer simultaneously. In CNGA, the highly interconnected porous network renders numerous pathways for rapid mass transport, strong adsorption and multireflection of incident light; meanwhile, the large planar interface between g-C3N4 and GO nanosheets increases the active site and electron transfer rate. Consequently, the methyl orange removal ratio over the CNGA photocatalyst reaches up to 92% within 4 h, which is much higher than that of pure g-C3N4 (12%), 2D hybrid counterpart (30%) and most of representative g-C3N4-based photocatalysts. In addition, the dye is mostly decomposed into CO2 under natural sunlight irradiation, and the catalyst can also be easily recycled from solution. Significantly, when utilized for CO2 photoreduction, the optimized CNGA sample could reduce CO2 into CO with a high yield of 23 mmol g(-1) (within 6 h), exhibiting about 2.3-fold increment compared to pure g-C3N4. The photocatalyst exploited in this study may become an attractive material in many environmental and energy related applications.

Ionic liquid self-combustion synthesis of BiOBr/Bi24O31Br10 heterojunctions with exceptional visible-light photocatalytic performances

Heterostructured BiOBr/Bi24O31Br10 nanocomposites with surface oxygen vacancies are constructed by a facile in situ route of one-step self-combustion of ionic liquids. The compositions can be easily controlled by simply adjusting the fuel ratio of urea and 2-bromoethylamine hydrobromide (BTH). BTH serves not only as a fuel, but also as a complexing agent for ionic liquids and a reactant to supply the Br element. The heterojunctions show remarkable adsorptive ability for both the cationic dye of rhodamine B (RhB) and the anionic dye of methylene orange (MO) at high concentrations, which is attributed to the abundant surface oxygen vacancies. The sample containing 75.2% BiOBr and 24.8% Bi24O31Br10 exhibits the highest photocatalytic activity. Its reaction rate constant is 4.0 and 9.0 times that of pure BiOBr in degrading 50 mg L(-1) of RhB and 30 mg L(-1) of MO under visible-light (λ > 400 nm) irradiation, respectively, which is attributed to the narrow band gap and highly efficient transfer efficiency of charge carriers. Different photocatalytic reaction processes and mechanisms over pure BiOBr and heterojunctions are proposed.

Asymmetric zinc porphyrin-sensitized nanosized TiO2 for efficient visible-light-driven CO2 photoreduction to CO/CH4

Asymmetric zinc porphyrin was used as a novel sensitizer for the visible-light-driven activity of CO₂ photoreduction to CO/CH₄ in the gas phase.