The urgent need for sustainable solutions to environmental challenges has led to significant research efforts towards innovative processes and technologies capable of addressing global issues such as carbon dioxide (CO2) capture and valorisation as well as efficient water-reuse cycles. The majority of processes involved in CO2 conversion require highly active catalysts for practical implementation. Concurrently, wastewater treatment technologies, critical for achieving sustainable water reuse, often rely on complex multi-stage systems that incorporate advanced oxidation processes (AOPs). Optimising reaction conditions and exploring unconventional approaches to catalytic system design are crucial for enhancing the efficiency of these processes. Among the emerging solutions, the application of thin-film catalysts deposited by cold plasma onto various structured supports has shown promising potential for improving process performance to meet environmental goals. This paper discusses recent advancements in the development of thin-film nanocatalysts based on cost-effective transition metals. It highlights their application in gas-phase reactions, such as CO2 hydrogenation to value-added products, as well as innovative uses in multiphase gas-liquid systems, including CO2 capture in aqueous solvents and the ozonation of wastewater.