Morphology-Controlled Silver-Containing Rhodium Nanoparticles for the Hydrogen Evolution Reaction

Abstract

Rh nanoparticles (RhNPs) and Rh-based alloys have attracted significant attention owing to their superior electrocatalytic activity in several energy conversion reactions. Three types of silver-containing RhNPs, namely, nanoshells, nanoframes, and porous nanoplates, have recently been synthesized via inverse directional galvanic replacement. These RhNPs were used here to elucidate the relationship between the morphology of RhNPs and their performance in the hydrogen evolution reaction (HER). The activity of RhNPs in HER was investigated using cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy. X-ray photoelectron spectroscopy and X-ray diffraction data revealed that RhNPs contain different Rh/Ag ratios. All RhNPs showed long-term stability in acidic conditions. In particular, nanoshells RhNPs exhibited better performance in the low overpotential range than those of Pt/C, a commercial Rh electrocatalyst, and other RhNPs. Thus, the morphology and composition of RhNPs can be controlled for efficient electrocatalysis.

Morphology‐ and composition‐controlled silver‐containing rhodium nanoparticles for the oxygen reduction reaction

“…The two semi-circles of pRhNPs may be related to the porous structure. 10 From the fitted data, the values of R 1 and Z w were found to be significant at high overpotentials (+0.3 and +0.4 V). However, sRhNPs exhibited a completely different trend compared to fRhNPs and pRhNPs.…”

“…This trend is similar to the experimental results of RhNPs for HER, which were previously published by our group. 10 Considering the higher favorability of the onset potential of sRhNPs for ORR compared to that of other RhNPs (Figure 2), the oxidation/reduction processes of the remaining Ag on the Rh surface were expected to promote ORR. To confirm this hypothesis, the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) data were analyzed (Figures S1, S2, and Table S1 in the Supporting Information).…”

“…Recently, three types of RhNPs, i.e., nanoshells (sRhNPs), nanoframes (fRhNPs), and porous nanoplates (pRhNPs), have been prepared by the inverse galvanic replacement method. 9,10 In a previous study, sRhNPs exhibited superior performance in HER. 10 In this study, these RhNPs were investigated to understand the relationship between their morphology and ORR activity.…”

“…9,10 In a previous study, sRhNPs exhibited superior performance in HER. 10 In this study, these RhNPs were investigated to understand the relationship between their morphology and ORR activity. The ORR performance and reaction mechanism were investigated by linear sweep voltammetry (LSV), Koutecky-Levich (K-L) plots, Tafel slopes, electrochemical impedance spectroscopy (EIS), and long-term stability measurements.…”