Role of Surface Defects and Optical Band-gap Energy on Photocatalytic Activities of Titanate-based Perovskite Nanomaterial

In recent years, water pollution has become one of the major challenges faced by humans because of consistent rise in population and industrial activities. Water pollution due to discharge from cosmetics and pharmaceutical wastes, organic dyes, and heavy metal seen as carcinogens has the potential to disrupt hormonal processes in the body. Different approaches such as chlorination, aerobic treatment, aeration, and filtration have been deployed to treat wastewaters before being discharged into the streams, lakes, and rivers. However, more attention has been accorded to treatment approaches that involve use of nanomaterial due to non-secondary pollution, energy efficiency, and ease of operation. Titanate-based perovskite (TBP) is one of the most frequently studied nanomaterials for photocatalytic applications because of its stability and flexibility in optical band-gap modification. This chapter provided an overview of basic principles and mechanisms of a semiconductor photocatalyst, and current synthesis techniques that have been used in formulating TBP nanomaterial. The effect of reaction conditions and approaches such as doping, codoping, composites, temperature, pH, precursor type, surface area, and morphology on surface defects and optical band-gap energy of TBP nanomaterial was highlighted. Importantly, the impact of surface defects and optical band-gap energy of TBP on its photocatalytic activities was discussed. Finally, how to enhance the degradation efficiency of TBP was proposed

Effects of p-type-metal-doping (Ba, Cs, and Y) of the compact-TiO2 electron transporting layer on the photovoltaic properties of n-i-p perovskite solar cells

Tailoring of charge transport properties of the electron transport layer (ETL) in solution-processible solar cells is continuously addressed not only for the performance enhancements in perovskite solar cells but also in various other applications in nanotechnology. In this work, three p-type dopants: barium, cesium (Cs), and yttrium (Y) with varying crystal radii and charges are doped in the titanium dioxide (TiO2) material so as to modify the electrical and optical properties of the ETL. The pure and doped TiO2 films were prepared by spin-coating a sol–gel precursor and their effects on the crystal structure, morphology, optical, electrical and photovoltaic properties of the perovskite solar cells were studied and reported. Among them, Y-doped TiO2 with similar crystal radii as that of the host titanium atom showed an enhanced photo-conversion efficiency mainly contributed by enhanced open circuit voltage and fill factor. The power conversion efficiency (PCE) for the perovskite absorber layer on Cs- and Y-doped TiO2 show the maximum PCE of 2.81 and 4.50% respectively. These are encouraging results for optimizing the yttrium doping level and fabrication conditions to further push the performance indicators of PSCs

Disinfection of a farmstead roof harvested rainwater for potable purposes using an automated solar photocatalytic reactor.

Access to safe and reliable water supply is a challenge in many parts of the developing world. The use of roof harvested rainwater for domestic and potable purposes is common in households and farmsteads in the rainforest and some parts of savannah ecological zones of  Nigeria in spite of  the health risk associated with ingestion of water from an unimproved source such as untreated roof harvested rainwater. Solar photocatalysis has been proven to be effective in water treatment devoid of the short comings of high fuel cost and formation of carcinogens associated with conventional households water disinfection methods such as boiling and the use of chemicals.  In this study, an automated photocatalytic batch reactor which uses solar radiation as its photon source was developed with materials sourced locally in Nigeria. The automated system  injects contaminated water into the reactor tube and evacuates the water into the treated water tank upon the reception of a preset solar radiation dose. Roof harvested rainwater from a farmstead inoculated with E.coli was used in the evaluation. Results from the experiments show that the  automated photocatalytic batch reactor was faster in bacteria inactivation than other reactors without TiO2 insert. A solar radiation dose of 160 kJ/L received on the photocatalytic reactor effectively and consistently inactivated  E. coli concentrations of 107 ± (1.3 x 106) CFU/ml to concentrations below the detection limit of 4 CFU/ml as well as prevent E. coli regrowth after 24 hrs storage in the dark. The use of this system as a point-of- use water disinfection system could enhance access to potable water in remote places such as farmsteads.

Electronic thermal conductivity, thermoelectric properties and supercapacitive behaviour of conjugated polymer nanocomposite (polyaniline-WO

A facile two-step, binder-free, chemical bath deposition (CBD) method was successfully employed in the synthesis of WO3 nanograins onto the matrix of conjugated polymer (polyaniline). The X-ray diffraction (XRD) results showed that the nanocomposite retained monoclinic phase of WO3 even when dispersed in polyaniline matrix. Owing to the synergistic effect offered by both the nanocomposite and structured metal oxide which may enhance the surface area, polyaniline-WO3 nanocomposite exhibited good specific capacitance. Polyaniline-WO3 yielded maximum specific capacitance ~96 F/g at scan rate of 5 mV/s in 0.5 M H2SO4 electrolyte. With the electronic thermal conductivity showing strong dependence on temperature, the estimated dimensionless figure of merit zT ~ 10−3 shows that the polymer nanocomposite (PNC) is promising as a new type of thermoelectric material. The electrochemical impedance spectroscopy showed that the PNC exhibited both pseudocapacitive and electric double layer capacitance behaviour