posted on 2021-01-21, 15:35authored byVedran Jovic, Armando Consiglio, Kevin E. Smith, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, Domenico Di Sante, Simon Moser
The
active (110) surface of the benchmark oxygen evolution catalyst
RuO2 spans a flat-band surface state (FBSS) between the
surface projections of its Dirac nodal lines (DNLs) that define the
electronic properties of this functional semimetal. Monitoring well-known
surface adsorption processes of H2, O2, NO,
and CO by in operando angle-resolved photoemission
spectroscopy, we selectively modify the oxidation state of individual
Ru surface sites and identify the electronic nature of the FBSS: stabilized
by bridging oxygen Obr pz, the FBSS disperses
along ⟨001⟩ oriented chains of bridging Rubr 4dz2 orbitals, collapses
upon Obr removal, yet remains surprisingly unaffected by
the oxidation state of the undercoordinated 1f-cus-Ru species. This
directly reflects in the ability of RuO2(110) to oxidize
CO and H2 along with its inability to oxidize NO, demonstrating
the FBSS’s active role in catalytic charge transfer processes
at the oxygen bridge sites. Our synergetic approach provides momentum-resolved
insights to the interplay of a catalyst’s delocalized electronic
band structure and the localized orbitals of its surface reactantsa
route toward a microscopic understanding of heterogeneous catalysis.