Synthesis of Pt Carbon Aerogel Electrocatalysts with Multiscale Porosity Derived from Cellulose and Chitosan Biopolymer Aerogels via Supercritical Deposition for Hydrogen Evolution Reaction

The aim of this study is to investigate the activity and stability of carbon aerogel-supported platinum electrocatalysts in the hydrogen evolution reaction, compared to current solutions based on carbon black. Self-synthesized carbon aerogels (pyrolyzed cellulose, and chitosan-based aerogels) with multiscale porosity and high overall specific surface area (up to ≈2500 m² g⁻¹), as well as Vulcan XC-72R supports were loaded via supercritical deposition (SCD) with platinum nanoparticles (mean particle diameter ≈1.3–2.0 nm, 2.8–3.8 wt% Pt loading). Overpotentials ranged from 46.5 to 50.0 mV at 10 mA cm⁻², whereas self-synthesized electrocatalysts had similar overpotentials as compared to a commercial catalyst with ≈8–10 times higher Pt loading. In addition, Pt-carbon aerogel electrocatalysts had higher stability and durability as compared to Pt-Vulcan, most probably due to the high micro- to mesoporosity of carbon aerogels, which promotes nanoparticle stability. The current density at 40 mV for Pt-Vulcan decreased by 80% after 20 h, whereas an insignificant drop was observed for Pt-carbon aerogels. These results show that the applied combination of materials (biopolymer-based carbon aerogels) and loading method (SCD) are a promising approach for synthesizing stable electrocatalysts with reduced platinum content for green hydrogen production.