Au Dendrite Electrocatalysts for CO2 Electrolysis

Journal Article (2018)
Author(s)

N.T. Nesbitt (Boston College)

M. Ma (TU Delft - ChemE/Materials for Energy Conversion and Storage)

Bartek J. Trześniewski

Samantha Jaszewski (Boston College)

Fazel Tafti (Boston College)

Michael J. Burns (Boston College)

W. A. Smith (TU Delft - ChemE/Materials for Energy Conversion and Storage)

M.J. Naughton (Boston College)

Research Group
ChemE/Materials for Energy Conversion and Storage
DOI related publication
https://doi.org/10.1021/acs.jpcc.8b01831
More Info
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Publication Year
2018
Language
English
Research Group
ChemE/Materials for Energy Conversion and Storage
Issue number
18
Volume number
122
Pages (from-to)
10006-10016

Abstract

Electrochemical CO2 reduction can convert CO2 into fuels and valuable chemicals using renewable electricity, which provides a prospective path toward large-scale energy storage. Au nanostructured electrodes have demonstrated the best catalytic performance for CO2 conversion: high catalytic selectivity for CO formation at low overpotentials, high current density, and long-term durability. Here, we report selective electrocatalytic CO2 reduction to CO on nanostructured Au with various morphologies, prepared via electrocrystallization with a megahertz potential oscillation. X-ray diffraction showed that the proportion of {100} and {110} to {111} surfaces increased at more negative deposition potentials. Cyclic voltammetry showed the potential of zero charge on an Au film was approximately 0.35 V vs standard hydrogen electrode (SHE) and that the surface energy decreased by ∼1 eV/nm2 at -0.5 V vs SHE, tending to 0 within several volts in either direction. Scanning electron micrograms showed that the Au crystals grow primarily in the 〈110〉 directions. From these data, a model for crystallization from melts was adapted to calculate the roughening temperature of the {111}, {100}, and {110} Miller indices as 7000, 4000, and 1000 K, decreasing for more negative deposition potentials. This offers a framework for exposed facet control in electrocrystallization. In CO2 electrocatalysis, -0.35 V vs reversible hydrogen electrode was observed to be a turn-on potential for improved CO2 reduction activity; dendrites showed 50% Faradaic efficiency for CO production at more cathodic potentials. The Tafel slope was measured to be 40 mV/decade for {100} and {110}-rich Au dendrites and 110 mV/decade for {111}-dominated Au plates, suggesting the higher surface energy crystal facets may stabilize all of the CO2 reduction reaction intermediates.

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