Amorphous Iridium and Tantalum Oxide Layers Coated on Titanium Felt for Electrocatalytic Oxygen Evolution Reaction

The layer of electrocatalytic mixed oxides is known as a dimensionally stable anode (DSA) used in many industrial electrochemical processes. A layer of iridium oxide (IrO 2 ) and tantalum oxide (Ta 2 O 5 ) coated on a titanium (Ti) substrate electrode is active for oxygen evolution reaction (OER) in acidic solution. Herein, we used a porous Ti felt composed of microfibers as a conductive substrate for the IrO 2 -Ta 2 O 5 electrocatalytic layer. The effect of the Ti substrates and the calcination temperature on the electrocatalytic activity for OER was investigated by cyclic voltammetry in an acidic sulfate solution. The results show that the IrO 2 -Ta 2 O 5 layer on the porous Ti felt with a large surface area was more active than the layer on the conventional Ti plate. The electrocatalytic activity of IrO 2 -Ta 2 O 5 layers was maximized by calcination at 350 °C and decreased by increasing the calcination temperature with the decrease of the double-layer capacitance ( C dl ), which is recognized as an electrochemically active surface area (ECSA). The IrO 2 -Ta 2 O 5 thin layer on the Ti felt was amorphous in the measurement of X-ray diffraction and Raman spectroscopy. The amorphous layer was confirmed to have rare cracks, larger ECSA, and higher catalytic activity for OER. The overpotential required to reach the current density of 10 mA cm –2 was only 0.27 V. The constant current was the Faradaic current for water oxidation to evolve O 2 .