Electrodeposition and electrocrystallization of tellurium on glassy carbon electrode (GCE) from both TeO2 silica sol and TeO2 solutions were investigated by utilizing cyclic voltammetry and chronoamperometry, respectively. The experiment results indicated that TeO2 was reduced to Te and Te was then reduced to H2Te in TeO2 silica sal, which was similar to that in TeO2 solutions although the reduction process was promoted in silica sol. Chronoamperometry results indicated that current density contributions of nucleation (i(nucleation)) in current-time transients (CTTs) overlapped with the current density contributions of double-layer charging (i(DL)) in both of TeO2 silica sol and TeO2 solutions. An adsorption-nucleation model was proposed to analyze quantitatively the CTTs, which could separate the i(DL) and i(nucleation) perfectly. And tellurium electrocrystallization mechanisms were characterized as instantaneous nucleation with 3D growth (3DI) under diffusion control in both of the TeO2 sol and solutions. The diffusion coefficient of HTeO2+ in TeO2 sol was smaller than that in solution, which resulted in smaller nuclei number density. (C) 2012 Elsevier Ltd. All rights reserved.