Synthesis of Noble Monometal and Bimetal-Modified Lignin Nanofibers and Carbon Nanofibers Through Surface-Grafted Poly(2-(Dimethylamino)Ethyl Methacrylate) Brushes

Various noble monometallic and bimetallic nanoparticles, including Pd, Pt, Au, Pd/Pt, Pd/Au, and Pt/Au, deposited lignin nanofiber mats (LFMs), and lignin carbon nanofiber mats (LCFMs) were fabricated using a novel lignin fiber surface PDMAEMA brush-guided strategy. PDMAEMA brushes were immobilized on lignin nanofiber mat surfaces by surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP) in an aqueous solution followed by monometallic nanoparticle deposition. For the Pd and Pt nanoparticle-immobilized LFMs, the metallic ions were reduced using citric acid and ascorbic acid, respectively; however, for the Au nanoparticle-immobilized LFMs, in-situ reduction occurred via the reducing potential of the PDMAEMA. The process was repeated to produce the bimetallic, Pd/Pt, Pd/Au, and Pt/Au-immobilized lignin nanofiber mats. The resultant mono and bimetallic nanoparticle-immobilized LFMs were then carbonized to the corresponding metallic-modified carbon nanofibers. XPS, XRD, and SEM were used to confirm the uniformity of nanoparticle deposition and the metallic state on the lignin fiber and carbon nanofiber surfaces.