Review on Metals and Metal Oxides in Sustainable Energy Production: Progress and Perspectives

Abstract

The exponential population growth on earth has put an enormous strain on energy resources, which come in various forms like fossil fuels, geothermal energy, and so on. Currently, fossil fuels are fulfilling most of our energy requirements. However, their nonrenewable nature and the production of toxic and greenhouse gases have forced the research community to explore different renewable and nontoxic energy resources. Among different renewable energy resources, hydrogen is considered an important alternative energy source. However, the production of hydrogen (H 2 ) from water is a nonspontaneous process. Therefore, different processes like photocatalysis and photoelectrocatalysis are employed to carry out the water splitting. For these processes, there is a dire need to develop different substances that can act as catalysts. For energy applications, different metals (particularly noble metals) and metal oxides (mostly transition metal oxides) have shown promising catalytic applications in the past decade. Herein, we discuss the progress made in the synthesis of metal and metal oxide nanostructures, followed by a discussion regarding the advances made in the application of these nanostructures as photocatalysts, electrocatalysts, and photoelectrocatalysts. From an energy application standpoint, it is found that doping and heterostructure development are the most advantageous methods used to date to improve the efficiency of metal and metal oxide nanostructures. Also, the development of dye-sensitized metal oxide catalysts for energy applications is considered a powerful method to develop highly efficient photocatalysts and electro-/photoelectrocatalysts. Finally, the limitations and challenges facing the practical application of these nanostructures are also discussed.

Air Cathode Design for Light-Assisted Charging of Metal–Air Batteries: Recent Advances and Perspectives

“…The microstructure of the semiconductor is a critical factor that affects photocatalytic efficiency. 41 For instance, layered nanosheets not only facilitate the rapid transmission of photogenerated electron holes but also enable large-area two-dimensional nanomaterials to receive more light. To reduce the charging voltage of Li−O 2 batteries to 1.9 V (Figure 3a), Liu et al prepared ultralarge-sized siloxane nanosheets using a modified topochemical exfoliation method.…”

Advanced Hybrid Ceramics for Nuclear and Hydrogen Energy Applications

“…ZnO has band gap around 3.3 eV synonymous to TiO 2 . It is cheap, easy to synthesize, chemically stable, nontoxic and environmental friendly in nature [85][86][87] and has been proven by multiple studies that it is an outstanding catalyst for hydrogen generation through overall water splitting. However ZnO has some disadvantages including improper utilization of visible light, rapid recombination of photo-induced charge carriers, quick backward reactions.…”

Recent Trends in Sustainable Solar Energy Conversion Technologies: Mechanisms, Prospects, and Challenges

“…There are a couple of reviews published in the recent past that highlight the importance of different materials or engineering aspects of the resulting devices used in these technologies. − For example, Wang et al discussed the role of different semiconductor-based heterostructures fabricated for photocatalytic production of H 2 fuel . In another review, the authors highlighted different doping strategies to engineer the bandgap of different metal- and metal-oxide-based photocatalysts for efficient solar energy conversion .…”

“…There are a couple of reviews published in the recent past that highlight the importance of different materials or engineering aspects of the resulting devices used in these technologies. − For example, Wang et al discussed the role of different semiconductor-based heterostructures fabricated for photocatalytic production of H 2 fuel . In another review, the authors highlighted different doping strategies to engineer the bandgap of different metal- and metal-oxide-based photocatalysts for efficient solar energy conversion . Likewise, Ma and co-workers have reviewed how carbon dots help in the growth process of perovskite crystals and control the energy levels at the interfaces of different layers, such as hole transport layer (HTL) or electron transport layers (ETL), in these devices .…”

“…51 In another review, the authors highlighted different doping strategies to engineer the bandgap of different metal-and metal-oxide-based photocatalysts for efficient solar energy conversion. 52 Likewise, Ma and co-workers have reviewed how carbon dots help in the growth process of perovskite crystals and control the energy levels at the interfaces of different layers, such as hole transport layer (HTL) or electron transport layers (ETL), in these devices. 53 Paul et al reviewed the valorization of biomass using sunlight to obtain fine chemicals and green fuel.…”