Resolving the Two-Track Scaling Trend for Adsorbates on Rutile-Type Metal Oxides: New Descriptors for Adsorption Energies

Identifying the trends in the adsorption energy (AE) of a given intermediate is of fundamental importance theoretically and also vital for rational catalyst design but is far less known on important transition metal oxide (TMO) catalysts. Herein, we report adsorption trends of a wide range of adsorbates on a variety of rutile-type TMO surfaces. We show that all the adsorbates on surface metallic sites (Mcus) can be surprisingly classified into two cross-uncorrelated groups, which scale well with either oxygen AE (EO@M) or hydrogen AE (EH@M). Two new descriptors, that is, the dz2 electrons and valence electrons of the Mcus site, are identified for EO@M and EH@M with R2 = 0.95 and 0.91, respectively. Their different bonding natures are demonstrated to be the chemistry origin of these two adsorption classes. In contrast, AEs of all the adsorbates on the lattice Obri sites can simply correlate with EO@M. These results may have far-reaching implications in TMO catalysis.