Azmat Ali Khan

Bio: Azmat Ali Khan is an academic researcher from Universiti Teknologi Malaysia. The author has contributed to research in topics: Photocatalysis & Titanium carbide. The author has an hindex of 5, co-authored 9 publications receiving 214 citations. Previous affiliations of Azmat Ali Khan include Balochistan University of Information Technology, Engineering and Management Sciences.

Recent advancements in engineering approach towards design of photo-reactors for selective photocatalytic CO2 reduction to renewable fuels

Abstract: Photocatalytic conversion of CO2 to solar fuels, an artificial photosynthesis, is a promising solution to resolve the energy crisis and global warming issues. The overall efficiency of photo-reduction of CO2 to fuels can be improved through the development of highly efficient catalyst and suitable photoreactor configuration. Significant efforts have been devoted to the design and developments of photo-catalysts, but very little focus has been given towards photo-reactors development. In this perspective, this review presents state of the art accomplishments in photocatalytic CO2 reduction through engineering approach towards reactor configuration and design aspects. In the main stream, the perspectives of different types of photo-reactors employed for the photocatalytic conversion of CO2 has been discussed. Slurry, fixed bed and membrane photo-reactors have been identified as the main categories that are critically discussed based on their operational mode, type of bed, number of phases involved, membrane used and type of light source. Comparative analysis of photo-reactors is also being employed to improve selectivity and photo-conversion rates of these photo-reactors. The influence of the factors such as light position and distribution, material of construction, temperature and pressure on the production of fuels has also been explicated. Moreover, perspective gives an overview of basic principles, thermodynamics and mass transfer involved in photocatalytic conversion of CO2 to fuels. Finally, conclusions and future perspectives paves further improvements in the design of photo-reactors to be made to increase the efficiency of CO2 conversion to renewable fuels.

Well-designed 2D/2D Ti3C2TA/R MXene coupled g-C3N4 heterojunction with in-situ growth of anatase/rutile TiO2 nucleates to boost photocatalytic dry-reforming of methane (DRM) for syngas production under visible light

Abstract: Well-designed fabrication of 2D/2D g-C3N4/Ti3C2TA/R (CN/TCT) MXene heterojunction with in-situ growth of TiO2-nucleates for boosting photocatalytic dry reforming of methane (DRM) has been investigated. Samples were synthesized through controlled chemical etching process to construct a TiO2 (anatase/rutile) embedded Ti3C2 (TCT) with layer by layer construction of g-C3N4, resulting in higher visible light absorption and proficient charges separation. Etching Ti3AlC2 with HF (49 vol. %) produces more TiO2 compared with HF (39 vol. %), whereas, amount of TiO2 produced was dependent on reaction time. The CN/TCT composite exhibited H2 and CO rate of 51.24 and 73.31 μmole g-1 h-1, much higher than using CN and TCT. This reveals layered Ti3C2 sheets embedded anatase/rutile TiO2, enabling proficient charge carrier separation with light absorption. The effect of feed ratio (CO2/CH4) further confirmed efficient sorption process with good recyclability and would be beneficial to promote the conversion of CO2 and CH4 to syngas under visible light.

Indirect Z-Scheme Assembly of 2D ZnV2O6/RGO/g-C3N4 Nanosheets with RGO/pCN as Solid-State Electron Mediators toward Visible-Light-Enhanced CO2 Reduction

Abstract: Indirect Z-scheme assembly of graphene-bridged 2D ZnV2O6/pCN nanosheets composite has been fabricated by one-step solvothermal process and tested for photoinduced CO2 conversion under visible-light irradiations. The highest CH3OH production of 3488 μmol g-cat–1 was obtained over ZnV2O6/RGO/g-C3N4 composite, 1.02 and 1.25 times higher comparing to ZnV2O6/RGO and ZnV2O6/g-C3N4 samples, respectively. This enhanced efficiency can be ascribed to well-designed ternary heterojunction with hierarchical structure and efficient charges separation by RGO. More importantly, CH3OH yield was further improved by introducing RGO/pCN as an electron sink, which led to a 1.07 times higher yield than using only RGO. This reveals that ternary 2D ZnV2O6/RGO/pCN nanostructure has higher visible-light absorption, improved charge separation, and enhanced photocatalytic efficiency due to RGO/pCN as multiple mediators. The stability of composite catalyst also prevailed for 32 h for continuous CH3OH production. Therefore, structured...

Constructing a Stable 2D Layered Ti3C2 MXene Cocatalyst-Assisted TiO2/g-C3N4/Ti3C2 Heterojunction for Tailoring Photocatalytic Bireforming of Methane under Visible Light

Abstract: Fabrication of two-dimensional (2D) titanium carbide (Ti3C2) MXene nanosheets with a unique morphology coupled with a 2D g-C3N4/TiO2 heterojunction for hydrogen-rich syngas production during photoc...

Titanium Carbide (Ti3C2) MXene as a Promising Co-catalyst for Photocatalytic CO2 Conversion to Energy-Efficient Fuels: A Review

Abstract: Photocatalytic CO2 reduction to produce valuable chemicals and fuels using solar energy provides an appealing route to alleviate global energy and environmental problems. However, available semicon...

Z-Scheme Photocatalytic Systems for Carbon Dioxide Reduction: Where Are We Now?

Abstract: Transforming CO2 into fuels by utilizing sunlight is promising to synchronously overcome global warming and energy-supply issues. It is crucial to design efficient photocatalysts with intriguing features such as robust light-harvesting ability, strong redox potential, high charge-separation, and excellent durability. Hitherto, a single-component photocatalyst is incapable to simultaneously meet all these criteria. Inspired by natural photosynthesis, constructing artificial Z-scheme photocatalysts provides a facile way to conquer these bottlenecks. In this review, we firstly introduce the fundamentals of photocatalytic CO2 reduction and Z-scheme systems. Thereafter we discuss state-of-the-art Z-scheme photocatalytic CO2 reduction, whereby special attention is placed on the predominant factors that affect photoactivity. Additionally, further modifications that are important for efficient photocatalysis are reviewed.

A review on photochemical, biochemical and electrochemical transformation of CO2 into value-added products

Abstract: Carbon dioxide (CO2), a greenhouse gas is considered to contribute significantly to climate change and global warming. Environmental changes require to minimize the measure of CO2 in air. The capture, storage and utilization of carbon based on photochemical, biochemical and electrochemical processes are the innovative proposed methods to decrease utilization of nonrenewables such as coal and oil. CO2 can be reduced chemically through either homogeneous or heterogeneous pathway. In general, photochemical transformation of CO2 involves formation of carrier charges followed by its separation, transportation and finally reduction of CO2 using generated photoelectrons. Photocatalytic reduction of carbon dioxide is a rising territory of research. Beginning from the premise of photocatalytic reduction, the investigations about different semiconducting frameworks like oxides, sulfides, and phosphides are considered in this review. Biochemical transformation deals with enzymatic conversion of CO2 and electrochemical reduction uses electrical energy for converting CO2 into its reduced form. The enzyme catalytic carbon dioxide change gives an eco-accommodating approach to make carbon-based chemical products. A few favorable circumstances related with enzymatic change incorporate high selectivity, high return, less quantity of waste, less response conditions however certain downsides, for example, staggering expense of catalysts and cofactors, and longer response times as contrasted and normal strategies. Some products obtained as a result of CO2 reduction includes methanol, formic acid, CO, methane, ethylene and gasoline. In this review, a overview on inalienably associated methodologies is given and ongoing advancement on the improvement, designing, and comprehension of CO2 reduction using photochemical, biochemical and electrochemical is outlined.

Nanostructured Carbon Nitrides for CO2 Capture and Conversion

Abstract: Carbon nitride (CN), a 2D material composed of only carbon (C) and nitrogen (N), which are linked by strong covalent bonds, has been used as a metal-devoid and visible-light-active photocatalyst owing to its magnificent optoelectronic and physicochemical properties including suitable bandgap, adjustable energy-band positions, tailor-made surface functionalities, low cost, metal-free nature, and high thermal, chemical, and mechanical stabilities. CN-based materials possess a lot of advantages over conventional metal-based inorganic photocatalysts including ease of synthesis and processing, versatile functionalization or doping, flexibility for surface engineering, low cost, sustainability, and recyclability without any leaching of toxic metals from photocorrosion. Carbon nitrides and their hybrid materials have emerged as attractive candidates for CO2 capture and its reduction into clean and green low-carbon fuels and valuable chemical feedstock by using sustainable and intermittent renewable energy sources of sunlight and electricity through the heterogeneous photo(electro)catalysis. Here, the latest research results in this field are summarized, including implementation of novel functionalized nanostructured CNs and their hybrid heterostructures in meeting the stringent requirements to raise the efficiency of the CO2 reduction process by using state-of-the-art photocatalysis, electrocatalysis, photoelectrocatalysis, and feedstock reactions. The research in this field is primarily focused on advancement in the synthesis of nanostructured and functionalized CN-based hybrid heterostructured materials. More importantly, the recent past has seen a surge in studies focusing significantly on exploring the mechanism of their application perspectives, which include the behavior of the materials for the absorption of light, charge separation, and pathways for the transport of CO2 during the reduction process.