Why the abnormal phenomena of D-band center theory exist? A new BASED theory for surface catalysis and chemistry

Since the D-band center theory was proposed, it has been widely used in the fields of surface chemistry by almost all researchers, due to its easy understanding, convenient operation and relative accuracy. However, with the continuous development of material systems and modification strategies, researchers have gradually found that D-band center theory is usually effective for large metal particle systems, but for small metal particle systems or semiconductors, such as single atom systems, the opposite conclusion to the D-band center theory is often obtained. To solve the issue above, here we propose a bonding and anti-bonding orbitals stable electron intensity difference (BASED) theory for surface chemistry. The newly-proposed BASED theory can not only successfully explain the abnormal phenomena of D-band center theory, but also exhibits a higher accuracy for prediction of adsorption energy and bond length of intermediates on active sites. Importantly, a new phenomenon of the spin transition state in the adsorption process is observed based on the BASED theory, where the active center atom usually yields an unstable high spin transition state to enhance its adsorption capability in the adsorption process of intermediates when their distance is about 2.5 Å. In short, the BASED theory can be considered as a general principle to understand catalytic mechanism of intermediates on surfaces.