Hydrogen spillover depicts the dynamic migration of surface adsorbed hydrogen species from hydrogen-rich sites to hydrogen-poor sites. It plays an important role in many H-involving reaction processes.
In order to enhance the catalytic performance of H-involving reactions, it is important to understand the detailed mechanism of hydrogen spillover, and uncover how hydrogen transfers and what factors control hydrogen conductivity on solid surface.
Recently, a research team led by Prof. MU Rentao and Prof. FU Qiang from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) directly observed the acceleration of hydrogen spillover via surface-lattice-confinement effect.
This work was published in Nature Communications on February 04.
Schematic of high pressure scanning tunneling microscopy (HP-STM) using a STM tip to probe the hydrogen spillover on MnO and Mn3O4 surfaces in H2 atmosphere (Image by MU Rentao and LIU Yijing)
The researchers constructed stripe-like MnO(001) and grid-like Mn3O4(001) monolayers on Pt(111) substrate, and investigated their hydrogen spillover atop by a combination of surface science investigation and theoretical calculation.
They found that hydrogen species from Pt diffused unidirectionally along the stripes on MnO(001), whereas it exhibited an isotropic pathway on Mn3O4(001).
Moreover, by using dynamic surface imaging in H2 atmosphere, they revealed that hydrogen diffused four times more rapidly on MnO than the case on Mn3O4, which was promoted by one-dimension surface-lattice-confinement effect.
Theoretical calculations indicated that a uniform and medium O-O distance favored hydrogen diffusion while low-coordinate surface O atom inhibited it.
"Our study illustrates the surface-lattice-confinement effect of oxide catalysts on hydrogen spillover and provides a promising route to improve the hydrogen spillover efficiency." said Prof. FU.
This work was supported by the National Key R&D Program of China, the National Natural Science Foundation of China, and Photon Science Center for Carbon Neutrality.