Copolymer-templated nitrogen-doped carbon (CTNC) films deposited on glassy carbon were used as electrodes to study electrochemically driven hydrogen evolution reaction (HER) in 0.5 M H2SO4. The activity of these materials was extremely enhanced when a platinum counter electrode was used instead of a graphite rod and reached the level of commercial Pt/C electrodes. Postreaction scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) measurements of electrode surfaces revealed that incorporation of even extremely low amounts of Pt resulted in this considerable gain of HER activity. High resolution XPS analysis and density functional theory (DFT) calculations confirmed that pyridinic nitrogen atoms act as active sites for Pt coordination and deposition. The Pt can be incorporated in both molecular (Pt(2+)) and metallic (Pt(0)) form. This study shows that great caution must be taken when designing "metal-free" HER catalysts based on N-doped carbons.
Keywords: N-doped carbon; block copolymers; electrocatalysis; hydrogen evolution; platinum nanoparticles.