Dear Colleagues,

Due to their remarkable chemical stability and suitable electrical properties, functionalized carbon materials with different inorganic/organic moieties are required materials for emerging applications. This is especially true in the generation of hydrogen via electrocatalytic water splitting, overcoming the performance of fullerenes, carbon nanotubes, graphene or carbon dots alone. Among these, heteroatom (e.g., nitrogen)-doped carbon nanomaterials are efficient electrocatalysts for hydrogen evolution reactions (HERs). It is now known that the carbons in vicinity of nitrogen atoms (although not those directly linked to nitrogen) promote the HER most actively. On the other hand, binary metal-oxide-based catalysts have been proven to be more effective for water splitting catalyzed reactions than their single metal oxide counterparts for both oxygen evolution reactions (OERs) and HERs. In addition, the combination of carbon-based materials and binary oxides to make composite nanostructures is interesting not only because they display the individual properties of both components, but they also exhibit synergistic properties that are advantageous for both water-splitting catalysis (photoanode materials) and gas sensing applications. This Special Issue also covers applications in optoelectronic field/field emission displays, because undoped and doped oxide nanomaterials have strong luminescence, thermo-stability, and thermo-responsive emission properties. According to the successful results that have been obtained, oxide-carbon-based complexes are much stronger adsorbents than carbon materials in gas adsorption (the charge transfers to the NO₂ and CO gas molecules from these complexes are much more significant compared to those from carbon materials). Finally, synergistic effects between porphyrins (as versatile organic macrocycles) and carbon-based materials are offering the best molecular electrocatalysts with regard to oxygen reduction reactions (ORRs) yet reported, and are also acting as high-performance gas sensors. Metalloporphyrins have been shown to be an exceptionally efficient supported homogeneous catalysts for the reduction of carbon dioxide (CO₂) to CO in water once inserted in a flow cell. As a notable result, electronics fabricated from organic materials are much less toxic, easier to recycle, and scalable. This Special Issue also invites papers that envisage advances in methods and technologies used to realize porous multicomponent surface layers consisting of bimetallic oxide nanoparticles/porphyrins and carbon nanomaterials. Special attention will be dedicated to computational chemistry techniques employing density functional theory (DFT) to achieve a fundamental understanding of the relationships between structure, morphology and (electro)catalytic, sensing and luminescence properties of these composites. Usually, the revised Perdew–Burke–Ernzerhof functional is used for DFT calculations. Reactions involving a concerted proton-electron transfer will lead to surface intermediates. DFT has been proven successful in calculating and using the free energy of adsorption of reaction intermediates to determine the efficiency of electrocatalysts for reactions such as the oxygen evolution reaction. A constant energy difference between different key reaction intermediates will lead to scaling relationships which can be used to discover electrocatalytically active materials.

Dr. Eugenia Fagadar-Cosma
Dr. Mihaela Birdeanu
Dr. Isabela Costinela Man
Dr. Serban Stamatin
Guest Editors

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• carbon nanomaterials covered in this issue include: graphene, multi-walled nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs), graphene quantum dots, nanodiamonds, carbon nanofibers, carbon nitride and fullerenes
• doped and undoped binary oxides
• macrocyclic compounds (porphyrin derivatives and corroles)
• optical and luminescent properties
• metal-free carbon–nitrogen (N–C) composites
• transition-metal-incorporated carbon–nitrogen matrices
• cathode catalyzed membrane with porphyrins and carbon powder for ORR
• doped carbon xerogels functionalized with binary transition metal oxides for electrochemical activity for ORR
• oxygen reduction reaction mechanism and kinetics for fuel cell technologies
• binary oxides (Co–Ni, Sn-Co, Fe-Co)/carbon materials as supercapacitor electrode materials
• binary metal oxide electrocatalysts for efficient overall water splitting
• electrocatalytic water splitting
• density functional theory