2 research outputs found
Trends in Formic Acid Decomposition on Model Transition Metal Surfaces: A Density Functional Theory study
We present a first-principles, self-consistent
periodic density
functional theory (PW91-GGA) study of formic acid (HCOOH) decomposition
on model (111) and (100) facets of eight fcc metals (Au, Ag, Cu, Pt,
Pd, Ni, Ir, and Rh) and (0001) facets of four hcp (Co, Os, Ru, and
Re) metals. The calculated binding energies of key formic acid decomposition
intermediates including formate (HCOO), carboxyl (COOH), carbon monoxide
(CO), water (H<sub>2</sub>O), carbon dioxide (CO<sub>2</sub>), hydroxyl
(OH), carbon (C), oxygen (O), and hydrogen (H; H<sub>2</sub>) are
presented. Using these energetics, we develop thermochemical potential
energy diagrams for both the carboxyl-mediated and the formate-mediated
dehydrogenation mechanisms on each surface. We evaluate the relative
stability of COOH, HCOO, and other isomeric intermediates (i.e., CO
+ OH, CO<sub>2</sub> + H, CO + O + H) on these surfaces. These results
provide insights into formic acid decomposition selectivity (dehydrogenation
versus dehydration), and in conjunction with calculated vibrational
frequency modes, the results can assist with the experimental search
for the elusive carboxyl (COOH) surface intermediate. Results are
compared against experimental reports in the literature
Facile Synthesis of Palladium Right Bipyramids and Their Use as Seeds for Overgrowth and as Catalysts for Formic Acid Oxidation
Controlling
the shape and thus facets of metal nanocrystals is
an effective way to enhance their performance in catalytic reactions.
While Pd nanocrystals with a myriad of shapes have been successfully
prepared with good uniformity and in high yield, Pd right bipyramids
(RBPs) that have a singly twinned structure have been elusive. We
report a facile route based on polyol reduction for the synthesis
of Pd RBPs with purity >90% and sizes controlled in the range 5–15
nm. The success of our synthesis relies on the use of iodide ions
to manipulate the strength of an oxidative etchant and selectively
cap the Pd{100} facets. The as-prepared RBPs could serve as seeds
to generate a set of Pd nanocrystals with novel shapes and structures.
The RBPs also exhibited enhanced catalytic activity toward formic
acid oxidation, with a current density 2.5 and 7.1 times higher than
those of the single-crystal Pd nanocubes (which were also mainly covered
by {100} facets) and commercial Pd black, respectively