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) sp(2) 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. (c) 2018 Elsevier Ltd. All rights reserved.