https://phys.org/news/2018-07-catalytic-material-role.html

Using a combination of theoretical calculations and measurements with advanced analytical techniques, the research team investigated the interactions between an organometallic iridium catalyst and support materials composed of sulfated alumina and sulfated zirconia. These interactions took place during a catalytic reaction promoted by the organo-iridium species with the support materials.

Thanks to previous research, scientists had been aware of a catalysis pathway that involves the donation of protons from the sulfated metal oxides. The research team discovered a second pathway, a redox reaction involving the acceptance of electrons from the organometallic complex on the sulfated metal oxide surface. They also discovered that some sites on the sulfated metal oxide surface that had been proton-donating could be transformed into electron-accepting sites, thereby changing the organometallic catalyst's chemical behavior.