Nanoarchitectured <i>N</i>-Heterocyclic Carbene-Pt Nanoparticles on Carbon Nanotubes: Toward Advanced Electrocatalysis in the Hydrogen Evolution Reaction

In response to the need for sustainable energy, this study focuses on advancing the electrocatalytic Hydrogen Evolution Reaction (HER). Considering platinum-based catalysts' efficacy, but acknowledging their cost and scarcity implications, our work pursues Pt content minimization, simultaneously upholding catalytic efficiency. Our approach introduces a precisely engineered nanoarchitecture, leveraging multiwalled carbon nanotubes (MWCNTs) bearing anchored <i>N</i>-heterocyclic carbenes (NHCs). These carbenes form robust covalent bonds with ultrastable, highly crystalline, platinum nanoparticles (PtNPs), establishing MWCNTs-NHC-PtNPs as a highly efficient electrocatalyst. The synergistic effect of NHCs and triazole moieties facilitates controlled nanoparticle growth and stabilization, yielding 2.0 ± 0.3 nm, uniformly distributed {1 1 1}-faceted PtNPs. The as-obtained MWCNTs-NHC-PtNPs nanomaterial exhibits exceptional HER efficiency in 0.5 M H₂SO₄ with an overpotential of 77 mV at -10 mA cm^-2 and a 50 mV dec^-1 Tafel slope, despite containing a merely 0.4% Pt/C atomic ratio content, as determined by XPS. Notably, at 200 mV overpotential, the mass activity reaches 8.6 A/mg_Pt and the specific activity is 53 mA/cm²_Pt, highlighting the efficiency of each Pt site within this nanostructure. Cyclic voltammetry reveals a distinctive, reversible PtO/Pt redox process, demonstrating surface-controlled and diffusion-assisted kinetics with charge storage properties that stabilize the electrocatalyst's electron-surface and facilitate proton reduction. Equally important, the nanoarchitecture prevents aggregation and mitigates Pt irreversible oxidation, showcasing enhanced stability after extensive cycling and exposure to air. Comparative analyses with a control electrocatalyst lacking NHC-PtNPs ligation emphasize the unique role of NHC-Pt (0) bonding in enhancing electrocatalytic efficiency. Comprehensive surface and electronic property analyses validate the potential of the MWCNTs-NHC-PtNPs platform.