Single crystal tungsten oxide (WO(3)) nanoparticles were prepared via a microwave-assisted method. Electrochemical activity for hydrogen evolution reaction (HER) on WO(3) supported on carbon black (WO(3)/C) electrocatalyst was first studied in acid solution (0.5 M H(2)SO(4)) and alkaline solution (1.0 M KOH) at room temperature. The overall experimental results revealed that the electrocatalytic activity for HER on WO(3)/C is one order magnitude higher than those obtained with carbon black in 0.5 M H(2)SO(4) and is six times than in the case of carbon black in 1.0 M KOH. These results demonstrated that WO(3) could enhance the electrocatalytic activity for hydrogen evolution reaction in acid solution (0.5 M H(2)SO(4)) and alkaline solution (1.0 M KOH). On the other hand, the kinetic reaction mechanisms were discussed on WO(3)/C electrocatalysts and carbon black in acid solution and alkaline solution for HER. Consequently, the rate-determining step changed from Tafel to Volmer due to the incorporation of WO(3) in acid solution. However, the rate-determining step carries through Tafel reaction on both electrocatalysts in alkaline solution though WO(3) was introduced. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.