Exploring the use of carbon-based nanocatalysts for sustainable processes

In recent years, new schemes for the industrial system, from energy production to chemical synthesis, have been central to research. Elevated waste emissions and global warming threaten quality of life and future livability on the planet. Reducing emissions and transitioning to a circular economy with low environmental impact is therefore a top global priority. In this context, alternative processes are widely investigated, especially electrocatalytic and photocatalytic approaches where renewable resources are the main drivers. Besides sustainable energy sources, raw material choice is also crucial. Industrial catalysts mostly rely on expensive, scarce elements with supply risks. An effective solution is using earth-abundant carbon-based materials to partly or entirely replace traditional catalysts. Although considerable research focuses on metal-free materials, much remains to explore in this field. This thesis investigates electrocatalytic and photocatalytic processes, using carbon-based nanostructures (CNSs) coupled with non-precious metal-based catalysts. Thanks to the adaptability of CNSs, the dissertation explores diverse catalytic applications for sustainable chemical production. Proposed catalytic systems include: (a) a defective carbon nitride photocatalyst combined with a homogeneous nickel complex to drive dual photocatalysis for producing value-added organic molecules under visible light; (b) functionalized carbon nanohorns (CNHs) integrated with a bismuth-based catalyst to enhance electrocatalytic CO2 conversion into formic acid, creating an effective nanohybrid with reduced bismuth content; and (c) novel metal-free nitrogen-doped carbon materials derived from hyper-crosslinked polymers to study hydrogen peroxide electrosynthesis, investigating how structural, compositional, and textural properties relate to the catalysts’ behavior, activity, and selectivity. Across all research lines, the tuning and versatility of these carbon-based materials are designed for specific tasks: introducing functional groups on the carbon nitride surface to improve interaction with the nickel complex, exploiting the unique morphology of carbon nanohorns for close contact with the inorganic bismuth catalyst, and tuning graphitization and nitrogen doping of oxygen reduction reaction electrocatalysts. These studies, while not yet at industrial scale, offer valuable insights for future development, highlighting the potential of carbon-based catalysts in advancing sustainable catalysis.