Unique Size of Co Nanoparticles Encapsulated in N-Rich Carbon Structure Derived from Electrochemical Etching for Enhanced Electrocatalytic Hydrogen Evolution

Co nanoparticles with uniform size distribution are promising electrocatalysts for hydrogen evolution reaction. Herein, we synthesize Co nanoparticles encapsulated in in situ formed N-doped carbon and carbon nanotubes (CNTs) named as Co–N/C(CNTs) by low-temperature carbonization the organic–inorganic hybrid precursors. The as-prepared 4.55% Co–N/C(CNTs) shows the better hydrogen evolution reaction (HER) performance. As demonstrated in electrochemical measurements, 4.55% Co–N/C(CNTs) composite can achieve 10 mA cm–2 at the overpotential of 263 mV in 0.5 M H2SO4 at the first LSV curve. After electrochemical etching, which is carried out through the cyclic voltammetry (CV) cycle with different laps, a uniform Co nanoparticle with a diameter of around 7 nm encapsulated in N-doped carbon is obtained. The overpotential is 168 mV after 4000 times CV cycles and stabilizes at 180 mV after 6000 times cycles. Therefore, this work may provide an idea for the design of high activity HER electrocatalysts in acid solution.