# Facet Preferencing by Chemical Substitution Controls Semi-Hydrogenation Selectivity in Ternary Pyrite-Type Intermetallic Compounds

## TL;DR

This paper shows how substituting Pd with Au in a catalyst changes its surface structure, improving selectivity in hydrogenation reactions.

## Contribution

The study introduces a new strategy for enhancing catalytic selectivity through facet preferencing via chemical substitution.

## Key findings

- Substituting Pd with Au in PdSb2 leads to preferential exposure of the (100) crystal facet.
- The (100) facet shows higher alkene selectivity due to weaker alkene binding.
- This approach indirectly modifies active sites by altering the exposed crystal facets.

## Abstract

Intermetallic compounds
serve as model catalysts for selective
hydrogenation reactions, offering precise control over the active
site composition(s), geometric and electronic structure. The addition
of a third element to form a ternary intermetallic alters the exposed
crystal facet(s), demonstrating a strategy to impart improved catalytic
behavior in intermetallic catalysts. The site-specific substitution
of a small fraction of Pd atoms with Au in pyrite-type PdSb2 results in the preferential exposure of the (100) facet over the
(111) facet. Electron back scattered diffraction and density functional
theory calculations confirm the facet change upon the substitution
of Pd with Au to form the ternary Pd1–x
Au
x
Sb2 (0.075 ≤ x ≤ 0.25). The (100) facet demonstrates higher net
alkene selectivity due to significantly weaker alkene binding compared
to the (111) facet. Distinct from our prior work on chemical substitution
to directly alter the active site composition, this work demonstrates
the indirect modification of active sites via preferential facet exposure.