TY - JOUR

T1 - Self-Limiting Adsorption of WO3 Oligomers on Oxide Substrates in Solution

AU - Müllner, M.

AU - Balajka, J.

AU - Schmid, M.

AU - Diebold, U.

AU - Mertens, S.F.L.

PY - 2017/9/14

Y1 - 2017/9/14

N2 - Electrochemical surface science of oxides is an emerging field with expected high impact in developing, for instance, rationally designed catalysts. The aim in such catalysts is to replace noble metals by earth-abundant elements, yet without sacrificing activity. Gaining an atomic-level understanding of such systems hinges on the use of experimental surface characterization techniques such as scanning tunneling microscopy (STM), in which tungsten tips have been the most widely used probes, both in vacuum and under electrochemical conditions. Here, we present an in situ STM study with atomic resolution that shows how tungsten(VI) oxide, spontaneously generated at a W STM tip, forms 1D adsorbates on oxide substrates. By comparing the behavior of rutile TiO2(110) and magnetite Fe3O4(001) in aqueous solution, we hypothesize that, below the point of zero charge of the oxide substrate, electrostatics causes water-soluble WO3 to efficiently adsorb and form linear chains in a self-limiting manner up to submonolayer coverage. The 1D oligomers can be manipulated and nanopatterned in situ with a scanning probe tip. As WO3 spontaneously forms under all conditions of potential and pH at the tungsten-aqueous solution interface, this phenomenon also identifies an important caveat regarding the usability of tungsten tips in electrochemical surface science of oxides and other highly adsorptive materials. (Chemical Equation Presented).

AB - Electrochemical surface science of oxides is an emerging field with expected high impact in developing, for instance, rationally designed catalysts. The aim in such catalysts is to replace noble metals by earth-abundant elements, yet without sacrificing activity. Gaining an atomic-level understanding of such systems hinges on the use of experimental surface characterization techniques such as scanning tunneling microscopy (STM), in which tungsten tips have been the most widely used probes, both in vacuum and under electrochemical conditions. Here, we present an in situ STM study with atomic resolution that shows how tungsten(VI) oxide, spontaneously generated at a W STM tip, forms 1D adsorbates on oxide substrates. By comparing the behavior of rutile TiO2(110) and magnetite Fe3O4(001) in aqueous solution, we hypothesize that, below the point of zero charge of the oxide substrate, electrostatics causes water-soluble WO3 to efficiently adsorb and form linear chains in a self-limiting manner up to submonolayer coverage. The 1D oligomers can be manipulated and nanopatterned in situ with a scanning probe tip. As WO3 spontaneously forms under all conditions of potential and pH at the tungsten-aqueous solution interface, this phenomenon also identifies an important caveat regarding the usability of tungsten tips in electrochemical surface science of oxides and other highly adsorptive materials. (Chemical Equation Presented).

KW - Catalysts

KW - Interfaces (materials)

KW - Oligomers

KW - Oxide minerals

KW - Phase interfaces

KW - Scanning tunneling microscopy

KW - Solutions

KW - Substrates

KW - Adsorptive materials

KW - Chemical equations

KW - Electrochemical conditions

KW - Electrochemical surface science

KW - Point of zero charge

KW - Solution interface

KW - Submonolayer coverage

KW - Surface characterization

KW - Tungsten

U2 - 10.1021/acs.jpcc.7b04076

DO - 10.1021/acs.jpcc.7b04076

M3 - Journal article

VL - 121

SP - 19743

EP - 19750

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7447

IS - 36

ER -