Today, as a result of the advancement of technology and increasing environmental problems, the need for clean energy has considerably increased. In this regard, hydrogen, which is a clean and sustainable energy carrier with high energy density, is among the well-regarded and effective means to deliver and store energy, and can also be used for environmental remediation purposes. Renewable hydrogen energy carriers can successfully substitute fossil fuels and decrease carbon dioxide (CO₂) emissions and reduce the rate of global warming. Hydrogen generation from sustainable solar energy and water sources is an environmentally friendly resolution for growing global energy demands. Among various solar hydrogen production routes, semiconductor-based photocatalysis seems a promising scheme that is mainly performed using two kinds of homogeneous and heterogeneous methods, of which the latter is more advantageous. During semiconductor-based heterogeneous photocatalysis, a solid material is stimulated by exposure to light and generates an electron–hole pair that subsequently takes part in redox reactions leading to hydrogen production. This review paper tries to thoroughly introduce and discuss various semiconductor-based photocatalysis processes for environmental remediation with a specific focus on heterojunction semiconductors with the hope that it will pave the way for new designs with higher performance to protect the environment.

Waste-derived materials obtained from the recovery and recycling of electronic waste (e-waste) such as batteries and printed circuit boards have attracted enormous attention from academia and industry in recent years, especially due to their eco-friendly nature and the massive increment in e-waste due to technological development. Several investigations in the literature have covered the advances achieved so far. Meanwhile, photocatalytic applications are especially of interest since they maintain mutual benefits and can be used for H₂ production from solar water splitting based on semiconductor processing as a proper environmentally friendly technique for solar energy conversion. In addition, they can be utilized to degrade a variety of organic and non-organic contaminations. Nonetheless, to the best of the authors’ knowledge, there has not been any comprehensive review that has specifically been focused on e-waste-derived photocatalytic materials. In this regard, the present work is dedicated to thoroughly discussing the related mechanisms, strategies, and methods, as well as the various possible photocatalysts synthesized from e-wastes with some critiques in this field. This brief overview can introduce modern technologies and promising possibilities for e-waste valorization, photocatalytic processes, and new photocatalytic degradation methods of eco-friendly nature. This paper discusses various e-waste-obtained photocatalytic materials, synthesis procedures, and applications, as well as several types of e-waste, derived materials such as TiO₂, ZnO, indium tin oxide, and a variety of sulfide- and ferrite-based photocatalytic materials.