General Approach to the Synthesis of Metal Hybrid Carbon/Titania Aerogel for the Oxygen Reduction Reaction

A mass production route to catalysts for the oxygen reduction reaction (ORR) is crucial for their end-use application. To date, the direct manufacture of ORR catalysts through simple and economic manufacturing routes remains a challenge, with current approaches relying on convoluted processes using expensive components. Here, a straightforward and cost-effective method is developed to fabricate metal hybrid carbon/titania composite aerogels (CTA-M) as ORR catalysts, which was obtained via carbonizing metal hybrid resorcinol-formaldehyde (RF)/titania composite aerogels at 900 °C in an inert atmosphere. The effect of metal nitrate, including La, Sm, Zr, Cr, Fe, and Cu nitrates, on the structure and ORR performance was investigated. The high porosity and specific surface area enabled CTA-M with a high mass transfer performance. The high asymmetry of anatase leads to the presence of oxygen vacancies in the crystal structure of CTA-M, which maintains the electrostatic equilibrium of the crystal structure, which verifies that the catalytic activity of anatase is superior to that of rutile, whereas the non-homogeneous product enhances the electrical conductivity, which further affects the catalytic activity of the ORR. Trace metal doping can modulate the electronic structure and composition of CTA-M. Iron nitrate doping carbon/titania aerogel (CTA-Fe-A) showed the best pore structure and oxygen adsorption performance. The specific surface area and pore volume of CTA-Fe-A were 720 m² g^-1 and 1.12 cm³ g^-1, respectively. The onset potential, half-wave potential, and ultimate current density were 0.82 V, 0.74 V, and 4.96 mA cm^-2, respectively. It is expected that this synthesis technique and the resulting CTA-M could be used as a method for large-scale commercial production of ORR catalysts, thus enabling the use of these materials in a broad spectrum of industrial applications.