Octahedral PdAg@Pd core-shell nanocrystals with ultrathin Pd shells as highly efficient catalysts for formic acid dehydrogenation

Abstract

Development of a catalyst for formic acid decomposition into hydrogen and carbon oxide has been highlighted due to the potentiality of formic acid as a prospective hydrogen source. A highly active and selective catalyst is readily synthesized in aqueous solution via one pot synthesis of PdAg alloy octahedral nanocrystals (ONCs) followed by epitaxial deposition of Pd. The composition and thickness of the obtained PdAg@Pd core-shell ONCs can be controlled with slight modifications during synthesis, cutting across catalytic activity. The optimized structural conditions (Pd to Ag ratio of 3.5:1, Pd shell with 1.1 atomic layers) provide lowered activation energy and exceedingly high activity under ambient condition, represented by turnover frequency of $12260 h^{-1}$ (at $30^circ C$) and $21500 h^{-1}$ (at $50^ circ C$) as well as high selectivity. The remarkable catalytic activity comes from the combination of the electronic promotion of Ag on Pd and the lattice strain arising from the difference in lattice parameters between PdAg and Pd. Thus, our design paves a synthetic route to develop a nanocatalyst with efficient hydrogen storage in formic acid and enhanced performance of proton exchange membrane fuel cell.