Acidity‐Mediated Metal Oxide Heterointerfaces: Roles of Substrates and Surface Modification

Abstract

Abstract Although strong modulation of interfacial electron concentrations by the relative acidity of surface additives is suggested, direct observation of corresponding changes in surface conductivity, crucial for understanding the role of local space charge, is lacking. Here, a model platform comprising well‐aligned mixed ionic‐electronic conducting Pr 0.2 Ce 0.8 O 2‐δ nanowire arrays (PCO NA ) is introduced to show that acidity‐modulated heterointerfaces predict electron depletion or accumulation, resulting in tunable electrical properties. Three orders of magnitude increased PCO NA conductivity are confirmed with basic Li 2 O infiltration. Moreover, the relative acidity of the insulating substrate supporting the PCO NA strongly influences its electronic properties as well. This strategy is further validated in purely ionic‐conducting nanostructured ceria as well as PCO NA . It is suggested that observed conductivity changes stem not only from acidity‐mediated space charge potentials at heterointerfaces but also from grain boundaries, chemically‐modulated by cation in‐diffusion. These findings have broad implications for how substrate and surface treatment choices can alter the conductive properties of nanostructured functional oxides.