Cobalt nanocrystals embedded into N-doped carbon as highly active bifunctional electrocatalysts from pyrolysis of triazolebenzoate complex

A new and highly-efficient electrocatalyst, constructed by surface enwraped Co nanocrystyals (NCs) embedded into 2-dimensional N-doping graphitized carbon layer (Co@NC), is synthesized by simple one-pot thermal treatment of complex Co(tzbc)₂(H₂O)₄ (tzbc = 4-(1H-1,2,4-triazol-1-yl) benzoate). The utilization of stoichiometrically clear Co(tzbc)₂(H₂O)₄ as precursor could reap following benefits: i) sp² carbon and nitrogen in tzbc groups could directly convert to N-doping graphitized carbon; ii) metallic Co NCs formed from the thermal reduction of Co²⁺ in Co(tzbc)₂(H₂O)₄, which can subsequently catalyze the graphitization of the obtained carbons, avoiding additional reducing agent or using potentially dangerous atmosphere; iii) most importantly, complex precursor is easily available and could synthesize in a large scale by simple stirring reaction. As a result, the Co@NC catalyst exhibits excellent activity and stability toward both hydrogen and oxygen evolution reactions (HER and OER, respectively), approaching electrocatalytic performance shown by state-of-the-art Pt and RuO₂. Such excellent HER and OER activities are attributed to the synergistic effect of the surface enwraped cobalt nanocrystyals and high conductivity of N-doped graphitized carbon.