The precise control of designing and synthesizing highly efficient water oxidation catalysts is a key role in enhancing the electrochemical processes such as water electrolysis. Herein, we fabricate the ultrafine Fe (variations on Fe amounts, chi(Fe) = M-Fe/M(Co+Fe)) and B modulated CoFeBO nanoparticles as efficient water oxidation precatalysts. In view of intrinsic amorphous nanostructure, optimal Fe-doping amounts and borate-rich CoFeOOH active nanosheets formed on the surface of CoFeBO nanoparticles during oxygen evolution reaction (OER) process, the CoFeBO (chi(Fe) = 0.3) precatalyst has demonstrated active electrochemical water oxidation properties under widen pH value from neutral to alkaline conditions. It exhibits only 263 mV in overpotential to reach a current density of 10 mA/cm(2) on glassy carbon (GC) electrode with the lowest Tafel slope of 39 mV/dec in 1 M KOH solution, which outperforms those of individual CoBO and FeBO as well as commercial RuO2 electrocatalyst in the same electrolyte. Moreover, continuous stability tests in 1 M KOH solution by recording potential response at 10 mA/cm(2) for 28 h and current response at overpotential of 270 mV for another 28 h show no obvious fluctuation. Combining the merits of cost-efficient, scalable synthesis and active water oxidation performances, amorphous CoFeBO nanoparticles could be employed as highly active OER precatalysts for OER. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.