Hydrogen (H₂) is a clean and efficient energy carrier, which can be directly used as a fuel in transportation and various applications. Water electrolysis is one of the most practical ways to produce pure hydrogen, and is well-suited in conjunction with solar energy sources. Although alkaline electrolysis is currently used for this purpose, polymer electrolyte membrane water electrolyser (PEMWE) has received much attention as a promising new alternative technology. Compared to the conventional alkaline electrolysis, PEMWE possesses confident advantages, which are high working current density, energy efficiency, easy operation, compactness and greater operating safety. However, the significant drawback of PEMWE is the high cost of the anodic electrocatalyst for oxygen evolution reaction (OER), which is typically based on precious metal oxide e.g. IrO₂ and RuO₂. Therefore, it is exceedingly important to reduce the amount of precious metals for the commercialization of PEMWE. One method of achieving this is to maximize the catalytic activity toward OER by controlling the shape of noble metal nanoparticles, and thereby reduce their usage in the system. Among various shape controlled structures, nanodendrite (ND) has attracted great interest because the rich edges and corner atoms derived from the dendritic structure are highly desired for improving the catalytic activity. Another approach to reduce the amount of noble metal is the use of an electrocatalyst supports, which may increase the specific surface area and hence the mass specific activity of the catalysts. Typically, carbon black has been used as catalyst support material. However, carbon material is easily corroded in the strongly oxidative condition of water electrolysers, and such electrochemical corrosion leads to the aggregation and migration of noble metal catalysts and even their detachment from the support surface with a loss of the electroactive surface area. In the present study, mesoporous ATO with high surface area (263 m² g^-1) was used as an electrocatalyst support. Ir-ND was synthesized to improve the catalytic activity for OER using tetradecyltrimethylammonium bromide (TTAB) as surfactant, which was loaded on prepared ATO. The electrocatalytic activity and stability of Ir-ND/ATO were investigated using cyclic voltammetry and galvanostatic mode. The physical properties were tested via XRD, BET and HR-TEM.