Non-conductive TiO_2 as the anode catalyst support for PEM water electrolysis

摘要

The applicability of a non-conductive TiO_2 as the support of the anodic catalyst for PEM water electrolysis was tested. Three TiO_2 samples with different specific surface areas were modified by IrO_2 using a modified version of the Adams fusion method. A constant weight ratio of IrO_2/TiO_2 of 0.6 was maintained in all cases. The size, specific surface area and morphology of IrO_2 electrocatalyst crystallites were investigated by X-ray diffraction, nitrogen adsorption (BET) and scanning electron microscopy, respectively. The electron conductivity of compressed catalyst powders was evaluated. Their electrochemical properties were studied on a rotating disk electrode (RDE) and finally in a laboratory electrolyser. Utilization of the TiO_2 support resulted in a reduction in the size of the IrO_2 crystallites. It was found that the lower the specific surface area of the supports, the higher was the electrochemical activity of the catalyst. This is most likely due to the formation of a conductive IrO_2 film on the surface of non-conductive supports. For the supports with a higher surface area, the amount of IrO_2 used was not sufficient to form an adequately compact film. This resulted in high electron resistance of such a catalyst. The RDE results were confirmed by a laboratory electrolysis test. Taken together with the excellent stability of TiO_2 in an anodic environment, these results suggest that these materials are promising supports if the appropriate amount of iridium is deposited.