Functionalized Ultrafine Rhodium Nanoparticles on Graphene Aerogels for the Hydrogen Evolution Reaction

Water electrolysis over a wide pH range offers promising technology for hydrogen production, which requires highly stable and active electrocatalysts for the hydrogen evolution reaction (HER). Herein, polyallylamine (PA)‐functionalized ultrafine rhodium nanoparticles (Rh−uNPs) uniformly anchored on three‐dimensional graphene aerogel (GA) nanocomposites (PA@Rh−uNPs/GA) are synthesized by using a facile surface adsorption‐chemical reduction method at room temperature. Physical characterization shows that the PA@Rh−uNPs/GA nanocomposites have three‐dimensionally porous architecture and that PA@Rh−uNPs with a 1.3 nm size are uniformly dispersed on the GA surface. Electrochemical measurements show that the molecular weight of PA affects the HER activity of PA@Rh−uNP nanocomposites. The molecular weight‐optimized PA@Rh−uNPs/GA nanocomposites with 10 % Rh mass show higher HER activity than the commercial 20 % Pt/C electrocatalyst over a wide pH range, which originates from proton or water enrichment at the electrode/solution interface due to the specific function of −NH 2 groups at PA molecules.