Reduced graphene oxide/InGaZn mixed oxide nanocomposite photocatalysts for hydrogen production

Carbon-based photocatalysts for hydrogen production: A review

Future energy crises and environmental deterioration may only be avoided by converting solar energy into sustainable, safe, cost-effective, and environmentally friendly technologies such as water splitting. Many researchers and governments throughout the globe have stressed the imperative need for affordable, environmental benign, resistive to corrosion, and earth-abundant nanostructured photocatalysts. This has led scientists to look for a green and cost-effective way to generate energy. As a result, the significance of photo catalyst engineering and reactor design difficulties connected to the performance of the photocatalytic reactions, as well as the examination and analysis of photocatalyst behaviors for adaptable and cost effective H2 production, is emphasized and summarized. The carbon-based materials have an appealing band structure, strong chemical stability, is plentiful on Earth, and is relatively easy to produce, making them suitable for hydrogen production. As example, graphene oxide (GO) with the oxygenated functional groups and graphene and its counterparts, including Graphene quantum dots (GQDs), GO, reduce graphene oxide (rGO), have been demonstrated to be ideal nanocomposite materials due to their superior properties and distribution in matrix and CNTs with excellent electronic transmission efficiency, low cost, stability, and environmental friendly are a great alternative of electron mediators for photocatalytic devices to boost light absorptivity for efficient hydrogen generation but some of them have limited photocatalytic activity due to their low sunlight usage efficiency, therefore the numerous methods, such as doping ions, constructing heterostructure, and functionalizing carbon-based materials, have recently been proven to promote the photocatalytic activity of them. The pore structure of carbon material functions as an acceptor of photogenerated electrons, improved the photocatalyst's specific surface area. Generally low-dimensional carbon materials demonstrated immense promise as highly efficient, low-cost, and environmentally friendly catalysts for hydrogen generation as an energy source. This article reviews the recent research progress on carbon-based materials for hydrogen evolution for the first time. It commences with a quick overview of the present state of affairs and fundamental concepts of hydrogen production in carbon-based nanomaterials for use in this field. We anticipate that this study will inspire readers to expand the use of carbon-based materials in H₂ generation in a more environmentally friendly way.

Non-magnetic and magnetically responsive support materials immobilized peroxidases for biocatalytic degradation of emerging dye pollutants-A review

In recent years, the removal of hazardous pollutants from many industries has become a significant challenge for mankind as a growing number of contaminants, including a wide range of organic pollutants, synthetic dyes, and polycyclic aromatic hydrocarbons (PAHs), have inevitably led to an increased anthropogenic impact on the biosphere. Due to the complex aromatic structure, most synthetic dyes show resistance to degrade by the classical approaches, such as coagulation, flotation, adsorption, membrane process, and reverse osmosis. Enzyme-assisted biodegradation of pollutants offers an eco-friendlier and cost-effective alternative to remediate dyes, dyes-based effluents, other toxins, etc. Various plant and microbial oxidoreductase (Horseradish and manganese peroxidase) have recently received more attention for degrading and detoxifying a wide range of dyes either by opening the aromatic ring structure or by precipitation due to their high activity under milder conditions, high substrate specificity, and biodegradable nature. To enhance the efficiency, stability and recyclability, enzymes were immobilized on various support media such as sodium alginate, agarose, chitin/chitosan, polyvinyl alcohol, polyacrylamide, macroporous exchange resins, hydrophobic sol-gels, and nanoporous silica gel, including magnetically separatable media. Among various types of magnetic nanoparticles (MNPs), iron oxide magnetic nanoparticles, such as hematite, magnetite, and maghemite, have gained great attention due to their properties like small size, superparamagnetism, high surface area to volume ratio, and ease of separation for repeated cycles of uses. These carriers can be separated easily and rapidly from the reaction medium by an external magnetic field without being subjected to mechanical stress than centrifugation or filtration. Various methods have been employed for immobilizing oxidoreductase on different media, such as adsorption, covalent binding, entrapment, and encapsulation using different cross-linking agents. Compared to the free enzyme, insolubilized enzymes reduce production costs by enzyme reusability, tolerance to unfavorable environmental conditions, and high catalytic stability. Here, we review various immobilization methods and biocatalytic degradation of emerging dye pollutants, focusing on various non-magnetically and magnetically responsive supports to immobilize peroxidases. Conclusively, magnetically separatable peroxidases show more stability towards extreme temperature and pH conditions and can be used for repeated cycles than free and non-magnetically separatable peroxidase.

Pyrochlore Ce2Zr2O7 decorated over rGO: a photocatalyst that proves to be efficient towards the reduction of 4-nitrophenol and degradation of ciprofloxacin under visible light

The synergistic interaction between phase pure Ce₂Zr₂O₇ and rGO enhances the photoreduction of 4-nitrophenol under visible light.

The Promoting Role of Different Carbon Allotropes Cocatalysts for Semiconductors in Photocatalytic Energy Generation and Pollutants Degradation

Semiconductor based photocatalytic process is of great potential for solving the fossil fuels depletion and environmental pollution. Loading cocatalysts for the modification of semiconductors could increase the separation efficiency of the photogenerated hole-electron pairs, enhance the light absorption ability of semiconductors, and thus obtain new composite photocatalysts with high activities. Kinds of carbon allotropes, such as activated carbon, carbon nanotubes, graphene, and carbon quantum dots have been used as effective cocatalysts to enhance the photocatalytic activities of semiconductors, making them widely used for photocatalytic energy generation, and pollutants degradation. This review focuses on the loading of different carbon allotropes as cocatalysts in photocatalysis, and summarizes the recent progress of carbon materials based photocatalysts, including their synthesis methods, the typical applications, and the activity enhancement mechanism. Moreover, the cocatalytic effect among these carbon cocatalysts is also compared for different applications. We believe that our work can provide enriched information to harvest the excellent special properties of carbon materials as a platform to develop more efficient photocatalysts for solar energy utilization.

Facile synthesis of nano-Zn/Bi–reduced graphene oxide for enhanced photocatalytic elimination of chlorinated organic pollutants under visible light

A Zn/Bi–RGO co-assembly was synthesized by a simple co-precipitation followed by hydrothermal process, and it exhibited enhanced visible light photocatalytic activity on remediation of chlorophenols.

Hierarchical Layered WS2 /Graphene-Modified CdS Nanorods for Efficient Photocatalytic Hydrogen Evolution

Graphene-based ternary composite photocatalysts with genuine heterostructure constituents have attracted extensive attention in photocatalytic hydrogen evolution. Here we report a new graphene-based ternary composite consisting of CdS nanorods grown on hierarchical layered WS2 /graphene hybrid (WG) as a high-performance photocatalyst for hydrogen evolution under visible light irradiation. The optimal content of layered WG as a co-catalyst in the ternary CdS/WS2 /graphene composites was found to be 4.2 wt %, giving a visible light photocatalytic H2 -production rate of 1842 μmol h(-1)  g(-1) with an apparent quantum efficiency of 21.2 % at 420 nm. This high photocatalytic H2 -production activity is due to the deposition of CdS nanorods on layered WS2 /graphene sheets, which can efficiently suppress charge recombination, improve interfacial charge transfer, and provide reduction active sites. The proposed mechanism for the enhanced photocatalytic activity of CdS nanorods modified with hierarchical layered WG was further confirmed by transient photocurrent response. This work shows that a noble-metal-free hierarchical layered WS2 /graphene nanosheets hybrid can be used as an effective co-catalyst for photocatalytic water splitting.

Visible-light-induced water reduction reaction for efficient hydrogen production by N-doped In2Ga2ZnO7 nanoparticle decorated on RGO sheets

Efficient hydrogen production over graphene-based N-doped In₂Ga₂ZnO₇ nanocomposite under visible irradiation.

An effective quaternary nano-sized Er3+:Y3Al5O12/Pt–PdS/ZnS visible-light photocatalyst for H2 production

The visible-light photocatalytic H₂ production activity of Er³⁺:Y₃Al₅O₁₂/Pt–PdS/ZnS was evaluated by using Na₂S and Na₂SO₃ as sacrificial reagents. Er³⁺:Y₃Al₅O₁₂, Pt and PdS can effectively improve the visible-light photocatalytic activity of ZnS.

Glimpses of the modification of perovskite with graphene-analogous materials in photocatalytic applications

This review highlights the recent trends in the modification of perovskite with graphene-analogous materials towards H₂production and pollutant degradation.

BaTiO3–graphene nanocomposites: synthesis and visible light photocatalytic activity

The new role of graphene as a macromolecular photosensitizer transforms the wide band gap BaTiO₃ to have visible light photoactivity.