Efficient solar driven photoelectrochemical (PEC) response by enhancing charge separation has attracted great interest in the hydrogen generation application. The formation of one-dimensional ZnO nanorod structure without bundling is essential for high efficiency in PEC response. In this present research work, ZnO nanorod with an average 500 nm in length and average diameter of about 75 nm was successfully formed via electrodeposition method in 0.05 mM ZnCl2 and 0.1 M KCl electrolyte at 1 V for 60 min under 70 °C condition. Continuous efforts have been exerted to further improve the solar driven PEC response by incorporating an optimum content of TiO2 into ZnO nanorod using dip-coating technique. It was found that 0.25 at % of TiO2 loaded on ZnO nanorod film demonstrated a maximum photocurrent density of 19.78 mA/cm2 (with V vs. Ag/AgCl) under UV illumination and 14.75 mA/cm2 (with V vs. Ag/AgCl) under solar illumination with photoconversion efficiency ~2.9% (UV illumination) and ~4.3% (solar illumination). This performance was approximately 3–4 times higher than ZnO film itself. An enhancement of photocurrent density and photoconversion efficiency occurred due to the sufficient Ti element within TiO2-ZnO nanorod film, which acted as an effective mediator to trap the photo-induced electrons and minimize the recombination of charge carriers. Besides, phenomenon of charge-separation effect at type-II band alignment of Zn and Ti could further enhance the charge carrier transportation during illumination.

The present paper reports on the facile formation of ZnO nanorod photocatalyst electrodeposited on Zn foil in the production of hydrogen gas via water photoelectrolysis. Based on the results, ZnO nanorod films were successfully grown via electrochemical deposition in an optimum electrolyte set of 0.5 mM zinc chloride and 0.1 M potassium chloride at pH level of 5-6 and electrochemical deposition temperature of around 70°C. The study was also conducted at a very low stirring rate with different applied potentials. Applied potential was one of the crucial aspects in the formation of self-organized ZnO nanorod film via control of the field-assisted dissolution and field-assisted deposition rates during the electrochemical deposition process. Interestingly, low applied potentials of 1 V during electrochemical deposition produced a high aspect ratio and density of self-organized ZnO nanorod distribution on the Zn substrate with an average diameter and length of ~37.9 nm and ~249.5 nm, respectively. Therefore, it exhibited a high photocurrent density that reached 17.8 mA/cm2under ultraviolet illumination and 12.94 mA/cm2under visible illumination. This behaviour was attributed to the faster transport of photogenerated electron/hole pairs in the nanorod’s one-dimensional wall surface, which prevented backward reactions and further reduced the number of recombination centres.

Palm oil (PO) is an edible vegetable oil that is extracted from the mesocarp of oil palm fruit (Elaeis guineensis), which is known to contain an almost equal proportion of saturated fatty acids (SFAs) and unsaturated fatty acids (USFAs). PO is used globally, because of its wide application as a frying medium. Extracted from the mesocarp of the oil palm fruit, PO needs to be processed to make it of edible quality. However, to meet growing global demand, it is often adulterated with recycled cooking oil (RCO), which is of inedible quality. As the methods of fresh palm olein (FPO) adulteration are sophisticated, it created an urgent need for commensurate analytical techniques with which to detect FPO adulteration. As such, chromatography and spectroscopy are commonly used to detect adulterations in edible oil. Therefore, this study evaluated the efficacy of utilising gas chromatography-mass spectrometry (GC-MS) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy to detect the adulteration of FPO with inedible RCO. Although previous studies attest to the efficacy of utilising GC-MS and ATR-FTIR spectroscopy in adulteration detection, both these techniques only provided specific qualitative and quantitative insights into the compounds present in oil samples. As such, further extensive studies on the application of a variety of adulteration detection methods are needed to provide regulatory authorities with information on the reliability of these modern adulteration detection methods.

Background: The conversion of sunlight to electrical power has been dominated by solidstate junction devices, often made of silicon. However, this dominance is now being challenged by the emergence of the new generation of water splitting cell (integration of photovoltaic system with an electrolyzer to generate clean and portable H2 energy carrier. This cell normally is based on nanocrystalline materials, which offers the prospect of cheap fabrication together with other attractive feature such as high chemical stability and flexibility in aqueous solution under evolving oxygen (O2) gases. However, nanocrystalline materials are facing few drawback such as recombination losses of charge carriers and less response under visible spectrum. Therefore, an effort to minimize the recombination losses of charge carriers and extended the spectral response of TiO2 NTs into visible spectrum by incorporating an optimum amount of lower band gap and suitable band edge position semiconductor (cadmium selenide [CdSe]) into the lattice of TiO2 NTs. Methods: An efficient approach has been demonstrated in this research work to enhance the solardriven photoelectrochemical (PEC) water splitting performance by decorating CdSe species into highly ordered TiO2 nanotubes (NTs) film through a facile and cost-effective chemical bath deposition. Morphology, chemical properties, and electronic structures have been studied. Results: A maximum photocurrent density of ~2.50 mA/cm2 at 0.6V versus Ag/AgCl electrode was exhibited by TiO2 NTs with the presence of approximately 1 at % of CdSe species. The presence of CdSe species offered an improvement of photocurrent density under solar irradiation due to the effective mediators to trap the photo-induced electrons and minimizes the recombination of charge carriers within the lattice of TiO2 NTs. Conclusion: Hybrid CdSe-TiO2 NTs were successfully fabricated through chemical bath deposition method in order to study the synergistic coupling effect of CdSe with TiO2 NTs on the PEC performance. By bathing pure TiO2 NTs film in a 5 mM CdSe precursor solution extensively covered by approximately 1 at % CdSe exhibited the highest jp of 2.50 mA/cm2 among the samples. However, excessive deposition (≥5 mM) was neither negatively affected by the self-organized NTs nor decreased in jp. This condition inferred that higher ionic product (Cd and Se ions) leaded to rapid ion-by-ion condensation or adsorption of colloidal particles clogged the opening pore’s mouth of TiO2 NTs. Thus, an improvement in the photoresponse was observed when optimum amount (~ 1 at %) of the CdSe was deposited on TiO2 NTs film.

A facile electrodeposition synthesis was introduced to prepare the nanodisk-dendritic ZnO film using a mixture solution of zinc chloride (ZnCl2) with potassium chloride (KCl) that acted as a directing agent. This study aims to determine the best photoelectrochemical response for solar-induced water splitting. Based on our results obtained, it was found that an average diagonal of nanodisk was approximately 1.70 µm with the thickness of ≈150 nm that was successfully grown on the surface of substrate. The photocatalytic and photoelectrochemical responses of the resultant wurtzite type based-nanodisk-dendrite ZnO film as compared to the as-prepared ZnO film were monitored and evaluated. A photocurrent density of 19.87 mA/cm2under ultraviolet rays and 14.05 mA/cm2under visible light (500 nm) was recorded for the newly developed nanodisk-dendritic ZnO thin film. It was believed that nanodisk-dendritic ZnO film can harvest more incident photons from the illumination to generate more photoinduced charge carriers to trigger the photocatalytic and photoelectrochemical reactions. Moreover, strong light scattering effects and high specific surface area of 2D nanostructures aid in the incident light absorption from any direction.