Control of the pore size distribution inside the RuO2 catalyst by using silica nanosphere particle for highly efficient water electrolysis

Abstract As state-of-the-art catalysts for polymer electrolyte membrane water electrolysis (PEMWE), IrO2 and RuO2 have been extensively developed to accelerate the oxygen evolution reaction (OER) and to achieve high stability under acidic conditions. In this study, RuO2 catalysts with controlled pore size distributions, particularly with a large number of macropores, are synthesized using a modified Adams method with silica nanosphere particles (SNPs) as a template. The specific surface areas of the prepared catalysts are 240–270 m2 g−1 regardless of the sizes of the SNP template. Also, all RuO2 catalysts have a rutile structure suggested from X-ray diffraction. The RuO2 catalysts with large portions of macropores (more than 20% of the total pore volume) exhibited greater OER activity and stability than the catalysts prepared using the conventional Adams method. These enhancements are attributed to fast mass transport during the reaction and the 50% increase in the electrochemically active surface area (ECSA) of the RuO2 catalysts prepared from the modified method over those prepared by the conventional Adams method. In addition, the enhanced catalytic activity (overpotential of 263 mV at 10 mA cm−2) of RuO2 with a large portion of macropores is revealed at the single-cell level in PEMWE.