Core–shell nanoparticles with tensile strain enable highly efficient electrochemical ethanol oxidation

Abstract

The ethanol oxidation reaction (EOR), the anode reaction of direct ethanol fuel cells, suffers from the sluggish oxidation kinetics and its low selectivity toward complete oxidation to CO2. The key...

Effects of Ligands on Synthesis and Surface‐Engineering of Noble Metal Nanocrystals for Electrocatalysis

“…The optical property evolution of the precursor solution can be explained by the change in the d orbitals of the Pd(II) center when coordinated to the glucose ligand, according to the crystal field theory. [28] The coordination substantially reduces the reduction potential of the PGM salt, which is the key to the suppression of the galvanic replacement reaction in this synthesis.…”

“…Because the galvanic replacement reaction arises from the reduction potential difference, it is rational to suppress the galvanic replacement reaction by engineering the reduction potential of the metal salt by coordinating a strong ligand to it. [14,[28][29][30][31] In an early effort, we demonstrated the efficacy of this strategy by synthesizing an Ag@Au core-shell nanostructure with the ligand of an iodide (I À ). [14] I À reacts with AuCl 4 À to form more stable AuI 4 À , accompanying a decrease in the standard reduction potential of the Au salt from 1.002 V (AuCl 4 À /Au) to 0.56 V (AuI 4 À /Au), which is a value even lower than that of the Ag salt (0.80 V).…”

“…As a demonstration, Ag@Pd core-shell nanoplates show substantially improved activity in the electrocatalytic ethanol oxidation reaction (EOR) (Figure 4e). [28] A mass activity of 12.7 A mg Pd À 1 was reported in 1.0 m KOH + 1.0 m EtOH, which has been attributed to the decreased energy barriers associated with the dehydrogenation of ethanol and the improved C2path selectivity of the ethanol oxidation toward the final product of CO 2 , thanks to the tensile strain in the Pd shells associated with the core-shell nanostructure.…”

“…[30] Similarly, Pd can grow on Ag nanocrystals to form an Ag@Pd core-shell nanostructure by employing glucose as the ligand for the Pd salt (Figure 4d). [28] The coordination of acetonitrile to the Pt(IV) salt was evidenced by NMR, as the 13 resulting coordination compound. [30] The coordination of glucose to the Pd(II) salt was demonstrated to show a gradual increase in the UV-vis absorbance, displaying a yellow color that deepened with time.…”

“…First, the ligand can substantially modify the reduction potential of noble metal salts, which enables the selfnucleation-free synthesis of noble metal nanocrystals on a large scale [23][24][25][26][27] and galvanic-replacement-free synthesis of a bimetallic core-shell nanostructure with a less-stable metal core and a noble metal shell. [14,[28][29][30][31] Second, some small-molecule ligands, sulfite for example, can initiate a mechanism resembling an electroless plating process for effective noble metal/non-noble metal co-reduction toward precisely controlled synthesis of alloy nanocrystals. [32,33] Moreover, the ligands may directly alter the surface properties of noble metal nanocrystals, leading to intriguing electrocatalytic properties (Figure 1).…”