The transition from fossil fuels to sustainable energy sources needs more efficient materials and improved technologies. Traditional materials (either pristine or their composites) are restricted by their low efficiency, low performance, short durability, environmental issues, high production costs, and narrow spectrum of applications. In recent years, the research in the field of materials for energy applications is very active as documented by the number of scientific contributions that is trending with exponential growth (Figure 1). Sept.This is a provisional file, not the final typeset article Furthermore, from a subject area standpoint, the field of "energy materials" is very broad and its relevant research is multidisciplinary. For example, the subject area can range from the materials for nuclear reactors harnessing nuclear energy to the materials for chemical energy storage. Even, the safety materials for energy technologies may qualify as "energy materials". Consequently, a journal issue on "energy materials" may include basic and fundamental scientific studies to more applicative contributions (Figure 2).For this reason, it is quite difficult to provide a complete overview over the energy materials. From the operational point of view, energy materials typically include materials for energy conversion, transport and storage. Topics are manifold, multifaceted, and sometimes very diverse. For example, the field of the electrical energy storage is very far from fuel storage. In any case, a very wide and transversal viewpoint in a specific field can make available a remarkable innovation. Of course, a look must always be directed towards new materials, fabricated experimentally (Uddin et al., 2014), or predicted theoretically (Sarker et al., 2013) and their properties (Zhang et al., 2019). For example, very recently the concept that uses the earth as a heat source and the night sky as a heat sink, known as thermoradiative photovoltaics (PV), has been demonstrated (Raman et al., 2019;Deppe and Munday, 2020). Materials for such devices will need a strong absorption and emission in the thermal radiation range, enough transparency to permit optical access to the night sky and have the potential to revolutionize the PV technology. Another look must always be oriented towards new characterization techniques and innovative methods. For example, in the specific field of lithium-ion batteries, the machine learning assisted statistical analysis together with experiment-informed mathematical modelling have been shown very recently by Jiang et al. (Jiang et al., 2020). The authors have correlated the degree of particle detachment cathodes with the charging rate and particle sizes. Alternatively, X-ray nano-computed tomography (CT) dual-scan superimposition technique has been adopted by (Lu et al., 2020) to shed light on microstructural heterogeneities, and how the performance of the lithium-ion batteries is affected under high rate conditions. The present article collection, composed of six research articles and three reviews, showcases some of the latest achievements and future perspectives in the field of the carbon-based and inorganic materials that are being designed to meet some of our energy challenges. It will be shown that the attention to the environment is a common perspective, due to preparation methods adopted from natural resources, polymers and the attempt to minimize (or replace) metals for a more sustainable development of technologies. Cesano et al. reviewed the topic of metal-free conductors based on macrosized and nanoscale carbons (i.e., carbon fibers, carbon nanotubes, graphene) from the viewpoint of the electrical and thermal conductivity for electronic and electrical wiring applications. Specifically, CNTs and graphene can be assembled into macroscopic fibers, yarns and ropes to be used as conductors (Akia et al., 2017;Jang et al., 2020). From the perspective of replacing metals, which are present in nature with limited amounts, the role played by the chemistry in helping to exceed the electrical conductivity of metals by means of the molecular-level control and doping, is emphasized. The contribution helps to elucidate most recent results in the field, and envisages new directions and potential applications. Jangir et al. designed and fabricated a bio-hybrid electrode, which integrates lithium (Li), sulfur (S), and molybdenum (Mo) in a nitrogen-doped reduced graphene oxide (NDRGO) matrix of biological origin. The obtained composite material works as an electrode, based on concepts of "embedded redox couples" and "induced electron transfer", behaving as a supercapacitor. Wu et al. reviewed MnO2/carbon composites for supercapacitors from the viewpoints of the synthesis and the electrochemical performance. Along with this broad theme, MnO2 has emerged as one of the most promising electrode materials for its specific capacitance, wide potential range, high electrochemical activity, and environmental friendliness. In addition, due to their low electrical resistance, significant thermal stability, large specific surface area, and porosity, carbon materials are ideal materials to be compounded with MnO2. The authors show the latest findings on MnO2/carbon supercapacitor electrodes, focusing on the fabrication strategies and the electrochemical performance influencing factors, with an outlook on the possible development directions in future for designing high-performance materials. for supercapacitor applications. The combination of Ni-Co LDHs with carbon-based materials gives a remarkable improvement in the specific energy, specific capacitance, and specific power performance of supercapacitors. The authors explore important factors influencing the synthesis of LDHs and the correlation among morphology, structure, and electrochemical performances of the NiCo LDHs. Improvements needed to increase the performance of these new supercapacitors are also provided. Kumar et al. synthesized hexagonal copper phosphide (Cu3P) platelets by CVD technique and incorporated it in the highly conducting 3D graphene scaffold (3DG), leading to the formation of Cu3P/graphene hybrid to be used as a coulombic efficient supercapacitor. The fabricated asymmetric supercapacitor (ASC) using Cu3P/graphene hybrid on graphite as cathode and activated carbon (AC) on graphite as anode showed high specific capacity, energy density, remarkable power density and an excellent life cycle. Li et al. fabricated spinel lithium manganese oxide (LiMn2O4) in Li-ion battery. The authors observed improved stability even at elevated temperature with the addition of 1, 3-propane sultone working as an electrolyte additive compared to the cell without additive. On the other hand, Gouda et al. fabricated membrane electrode assembly (MEA) in the proton exchange membrane fuel cells (PEMFC) using graphene materials obtained from the thermal dissociation of polyethylene terephthalate (PET), working as catalytic electrodes, and a ternary polymer blend (i.e. polyvinyl alcohol, polyethylene oxide, and polyvinyl pyrrolidone). The authors then investigated the effect of gas diffusion layers (GDL) and the number of catalyst layers in three types of MEAs. Alternatively, semiconductor nanowires have the potential to reduce costs and increase the efficiency of the devices. -doped cobaltite perovskite LaCoO3 particles as efficient catalysts for oxygen evolution reaction.Overall, the published papers in this issue cover materials for energy which are manifold, multifaceted, and sometimes very different from each other, but we can easily conclude that the theme will have significant developments in the coming years.
