Despite extensive studies to investigate photocatalysis towards environmental remediation, there is still much work to be done in the visible light sector. A major intellectual merit of our work is to utilize visible light active photocatalysts: to photo-transform and photo-degrade undesirable organic contaminants to desirable organic products; to photocatalytically produce H2 by coupling with a whole-cell biocatalyst; to photoreduce CO2 using a bi-functional nanocomposite; and to synthesize a core-shell heterostructured plasmonic photocatalyst for environmental remediation. The ultimate aim of our research is to promote sustainable pathways to address energy and environmental problems using visible light photocatalysis.
Synthesis of molecularly selective semiconductors for visible light photocatalysis as a green synthetic route towards organic synthesis
Common photocatalysts such as TiO2, tend to completely oxidize organic pollutants, and thus preclude the recovery of desirable intermediate products. The proposed research topic will comprehensively explore strategies for synthesizing visible light active molecularly selective photocatalyst in order to remove pollutants from aqueous systems as well establish a green synthetic route for the production of desirable organic products.
A visible light inorganic-bio hybrid photocatalysts for H2 production
Production of H2 by water-splitting provides a greener source for fuel (without the production of greenhouse gas, CO2), but is also an essential material for the organic chemical industry (e.g., Fischer-Tropsch reactions). Catalysts are a critical issue for H2 production, and there is intense interest in finding alternatives to noble metals (notably Pt) that are capable of converting water into H2. The cost and limited availability of Pt, coupled with its non-selectivity and poisoning by environmental pollutants, are major restrictions to future generation of H2 by renewable means.
An alternative approach is the use of enzymes known as hydrogenases which catalyze the reduction of protons into H2 at active sites composed of iron-iron or nickel/iron complexes. These enzymes can be coupled with electron-donating inorganic semiconductors, which upon light excitation, can transfer electrons directly to the adsorbed hydrogenase, and thus reduce H+ to H2.
Photocatalytic CO2 reduction using bi-functional nanocomposites
The capture and efficient use of CO2 is an important issue due to the fact that CO2 released by burning fossil fuels is a primary cause of global warming. One of the most promising solutions is to convert CO2 to valuable organic products by means of solar energy. Furthermore, the photoreduction of CO2 to energy sources such as CO, CH3OH, and CH4 is another viable strategy for reducing greenhouse gas levels and addressing the energy crisis simultaneously.
Efforts have been made to develop efficient heterogeneous photocatalysts for the reduction of CO2. Various photocatalysts, ranging from semiconducting materials like TiO2 to metal-incorporating zeolites have been investigated for their activity in photocatalytic CO2 reduction. However, most of the photocatalysts investigated are only active in the UV region and their efficiency for CO2 reduction is still quite low. This has been partly attributed to weak CO2 adsorption on the catalyst surface. Metal-organic frameworks (MOF), a class of porous crystalline materials formed by a network of metal ions/clusters linked by polydentate organic molecules, have emerged as an exciting potential CO2 adsorbent. The high adsorption properties have been attributed to their structural tunability, high surface area, and high selective CO2 adsorption capacity. Therefore, it is of great interest to develop highly efficient bi-functional nanocomposite that can reduce CO2 under visible light while having high CO2 adsorption capacity.
Synthesis and characterization of core-shell metal nanoparticle/photocatalyst for stability and recyclability applications of the plasmonic hybrid photocatalysis
Modification using silver (Ag) nanoparticles has been shown to improve the photocatalytic activity by hindering the electron-hole (e–/h+) recombination rate, as well as facilitating the electron excitation through a local electrical field. Due to the excellent plasmon resonant effect of the Ag nanoparticles, many traditionally UV light active photocatalysts, such as TiO2, have exhibited visible light photocatalytic activity. However, the exposed metal nanoparticles react with the surrounding medium during photocatalysis, resulting in the loss of the particles from the surface of the semiconductor. Thus, the synthesis of heterostructures with metal cores and semiconductor shells will provide both stability and enhanced photocatalytic activity under visible light irradiation.
The following is a list of instrumentation used in our research group. Contact Prof. Ismail if you are interested in collaborating using any of the below characterization techniques.
Scanning electron microscopy (SEM), X-ray powder diffractometer (XRD), Diffuse Reflectance UV-Vis spectrophotometer, FTIR spectrophotometer, zeta potential analyzer, dynamic light scattering particle size analyzer, 500 W Xe Arc Lamp, and many more.