Dry Plasma Synthesis of Nanohybrids and Nanofluids for Water Electrolysis: Toward CRM-Free, Green and Efficient Catalytic Materials

This work presents a dry and green synthesis approach using RF magnetron sputtering, a physical vapor deposition (PVD) technique, to develop nanohybrids (catalyst-coated powders) and nanofluids (nanoparticles suspended in liquids) catalysts for water electrolysis.1,2 The method eliminates hazardous chemicals and multi-step processes, enabling sustainable and scalable catalyst production.2 For nanohybrids, copper-coated multi-walled carbon nanotubes (Cu/CNTs) are synthesized by O₂ plasma treatment of CNTs followed by RF sputtering of Cu. A vibrating deposition stage ensured uniform nanoparticle coating. XPS confirmed enhanced surface functionality, while dynamic light scattering (DLS) and thermogravimetric analysis (TGA) revealed improved dispersion and material loading. Finally, the produced nanohybrids exhibited hydrogen evolution reaction (HER) activity. For nanofluids, gold nanoparticles (AuNPs) were sputtered directly into polyethylene glycol (PEG) and transferred into a Nafion ionomer to fabricate a catalyst-coated membrane (CCM). Characterization using UV-VIS, TEM, SEM, XPS, and AFM confirmed the preservation of nanoscale morphology and uniform dispersion. The resulting CCM exhibited excellent HER activity, with an onset potential of 50 mV and a Tafel slope of 38 mV/dec. This work demonstrates RF magnetron sputtering as a clean, scalable, dry synthesis technique for producing CRM-free, high-efficiency catalysts for sustainable hydrogen production through water electrolysis.