Water pollution has been a prevalent issue globally for some time. Some pollutants are released into the water system without treatment, making the water not suitable for consumption. This problem may lead to more grave problems in the future including the destruction of the ecosystem along with the organisms inhabiting it, and illness and diseases endangering human health. Conventional methods have been implemented to remove hazardous pollutants such as dyes, heavy metals, and oil but are incapable of doing so due to economic restraints and the inability to degrade the pollutants, leading to secondary pollution. Photocatalysis is a more recently applied concept and is proven to be able to completely remove and degrade pollutants into simpler organic compounds. Titanium dioxide (TiO2) is a fine example of a photocatalyst owing to its cost-effectiveness and superb efficiency. However, issues such as the high recombination rate of photogenerated electrons along with positive holes while being only limited to UV irradiation need to be addressed. Carbonaceous materials such as graphene oxide (GO) can overcome such issues by reducing the recombination rate and providing a platform for adsorption accompanied by photocatalytic degradation of TiO2. The history and development of the synthesis of GO will be discussed, followed by the methods used for GO/TiO2 synthesis. The hybrid of GO/TiO2 as a photocatalyst has received some attention in the application of wastewater treatment due to its efficiency and it being environmentally benign. This review paper thereby aims to identify the origins of different pollutants followed by the sickness they may potentially inflict. Recent findings, including that GO/TiO2-related nanocomposites can remove pollutants from the water system, and on the photodegradation mechanism for pollutants including aromatic dyes, heavy metal and crude oil, will be briefly discussed in this review. Moreover, several crucial factors that affect the performance of photocatalysis in pollutant removal will be discussed as well. Therefore, this paper presents a critical review of recent achievements in the use of GO/TiO2-related nanocomposites and photocatalysis for removing various pollutants in wastewater treatment.

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Textile dyeing wastewater becomes one of the root causes of environmental pollution. Titanium dioxide (TiO 2 ) is one of the photocatalysts that shows prominent organic dye photodegradation ability. In this study, a porous tungsten oxide (WO 3 )/ TiO 2 composite was prepared through ultrasonic-assisted solvothermal technique with varying amounts of WO 3 ranging from 0.25 to 5 weight % (wt.%). The prepared 0.50 wt.% WO 3 /TiO 2 (0.50WTi) composite exhibited the highest photodegradation activity (4.39 × 10 −2 min −1 ) and complete mineralization in chemical oxygen demand (COD) reading towards 30 mg.L −1 of Reactive Black 5 (RB5) dye under 60 min of light irradiation. Effects of large surface area, small crystallite size, high pore volume and size, and low electron-hole pair recombination rate attributed to the superiority of 0.50WTi. Besides, 0.50WTi could be reused, showing 86.50% of RB5 photodegradation at the fifth cycle. Scavenger study demonstrated that photogenerated hole (h + ) was the main active species of 0.50WTi to initiate the RB5 photodegradation. Cytotoxicity assessment determined the readings of half-maximal inhibitory concentration (IC 50 ) were 1 mg.mL −1 and 0.61 mg.mL −1 (24 and 72 h of incubations) for the 0.50WTi composite.

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Hydrogen (H2) has proved itself as a viable future energy carrier and alternative for fossil fuel in terms of ensuring a clean and sustainable energy supply. However, H2 must be made available at a lower cost so that everyone can benefit from it and prevent causing a worldwide ecological imbalance. The usage of photoelectrochemical water splitting (PEC) technology by using TiO2 photocatalyst can produce H2 using renewable solar energy. The essential milestones, as well as the mechanism in PEC H2 generation, are discussed in this article.