Can we judge an oxide by its cover? The case of platinum over α-Fe₂O₃ from first principles

Abstract

Metal/metal-oxide interfaces appear in a wide variety of disciplines including electronics, corrosion, electrochemistry, and catalysis. Specifically, covering a metal-oxide with a metal is often thought to enhance solar energy absorption and to improve photocatalytic activity. For example, the platinum/hematite (Pt/α-Fe2O3) interface has demonstrated improved functionality. In order to advance our understanding of how metal coverage over an oxide helps performance, we characterize the geometry and electronic structure of the Pt/α-Fe2O3 interface. We investigate the interface using density functional theory +U, and find a stable crystallographic orientation relationship: Fe2O3(0001)[11[combining macron]00]∥Pt(111)[101[combining macron]] that agrees with experiment. Furthermore, there are significant changes in the electronic structure of α-Fe2O3 as a result of Pt coverage. We therefore suggest the concept of "judging" the electronic properties of an oxide only with its cover. Specifically, covering Fe2O3 with Pt reduces carrier effective mass and creates a continuum of states in the band gap. The former could be beneficial for catalytic activity, while the latter may cause surface recombination. In order to circumvent this problem, we suggest putting metal coverage behind the oxide and far from the electrolyte in a photoelectrochemical device in order to quickly collect electron carriers and avoid recombination with vulnerable holes accumulating as a result of catalysis at the surface.

Charge Transport Calculation along Two‐Dimensional Metal/Semiconductor/Metal Systems

“…For convenience, we chose to use the metal/metal/semiconductor ordering (Figure b). The lattice constant of the unit cell is an average of the lattice constants of the metal and semiconductor contacting the system, as was suggested by . The system super cell contains ten metal monolayer (FeS 2 or VS 2 ) unit cells and five semiconductor monolayer (CrS 2 , MoS 2 or CrS 2 ) unit cells, 45 atoms (Figure ).…”

Unusual Photoactive Water Oxidation Activity of Pt/PtOx Cocatalyst Decorated Crystalline α‐Fe2O3 Nanostructures: Exposed Facets Dependent Reactivity

“…The overlaps of electronic states extend the charge carrier and exhibit synergic properties . Neufeld et al study on density functional theory calculation of Pt covered Fe 2 O 3 and show that strong hybridization between Fe and Pt states reduced the electron effective mass and improve the overall charge transport …”

The nature of the Pt(111)/α-Fe2O3(0001) interfaces revealed by DFT calculations

“…Pt(111) surface is often used as a substrate for α-Fe 2 O 3 (0001) thin film growth, because it is chemically inert, allows good epitaxy conditions and ensure conductive backcontact to improve the PEC activity in electrochemical devices. 10,21,[37][38][39][40] It is thus mandatory to determine the effect of Pt(111) substrate over hematite. In order to gather information about the chemical, structural and electronic properties in such interfaces, a molecular level investigation is required.…”

“…In order to gather information about the chemical, structural and electronic properties in such interfaces, a molecular level investigation is required. Despite numerous studies reported on α-hematite growth, mainly experimental 10,21,37,41,42 , but also some theoretical about sandwiched hematite 39,40 , the substrate-overlayer interface has not been resolved. In particular the termination (Feor O 3 ) of hematite interacted with platinum is not well-known.…”