Plasma Functionalization of Carbon-Based Materials for Electrocatalytic Applications

Carbon-based materials are widely employed in electrocatalytic energy conversion and storage technologies owing to their high electrical conductivity, chemical stability, tunable structure, and low cost. However, the limited intrinsic activity and surface inertness of pristine carbon materials often necessitate surface modification to generate catalytically active sites and improve interactions with reactants and electrolytes. Among the available approaches, plasma functionalization has emerged as a versatile, rapid, solvent-free, and potentially resource-efficient technique that enables systematic tuning of surface chemistry while often limiting modification primarily to the near-surface region. This review discusses the fundamentals of plasma-assisted surface modification of carbon materials, including plasma generation, reactive species, plasma-surface interaction mechanisms, and the influence of key processing parameters such as gas composition, power, pressure, and treatment time. Particular attention is devoted to plasma-induced heteroatom doping, defect engineering, surface functionalization, and the dynamic structural evolution of carbon frameworks during treatment. The impact of these modifications on the physicochemical properties and electrocatalytic performance of carbon materials is critically examined with respect to representative reactions, including the oxygen reduction, oxygen evolution, and hydrogen evolution reactions. The advantages, limitations, and scalability of plasma technologies are also discussed, along with current challenges in process control and reproducibility. Finally, future opportunities involving operando diagnostics, single-atom catalysts, advanced porous carbon architectures, and industrial-scale plasma processing are highlighted. Plasma processing offers a versatile route to carbon surface and catalyst-interface engineering, although standardized reporting and quantitative plasma-structure-performance relationships are still required for rational process design and scale-up.