Simultaneous
attainments of high conductivity and superior catalysis are major
challenges for amorphous electrocatalysts in carbon dioxide electroreduction
at high overpotential. In this study, one protocol is first demonstrated
to drive the shell amorphization of nanoporous Ag-Bi (a-NPSB) catalyst
with the spatially interconnected ligament during the initial stage
of CO2ER. This newborn a-NPSB bestows the outstanding catalysis,
evidenced by a Faradaic efficiency of 88.4% for formate production
at −1.15 V vs RHE, specific current density of 21.2 mA cm–2, and mass specific current density of 321 mA mg–1. The unique catalysis is considered as the collective
contribution of the conductive ligament internally and amorphous Bi2O3 shell with about 3.2 nm thickness externally.
Simultaneous obtaining of the conductivity of inner metals and catalytic
activity of the amorphous shell will pave a new avenue for designing
a robust electrode during electrochemical reaction.
We applied a DC electric field between two flat electrodes to attract thermally charged maghemite (γ-Fe(2)O(3)) nanocrystalline quantum dots dissolved in hexane to form smooth, robust, large area and apparently identical films of equal thickness on both electrodes. Visible microscopy, scanning electron microscopy, atomic force microscopy and profilometry showed that the electrophoretically deposited dot films were very smooth with an rms roughness of ∼10 nm for ∼0.2 µm thick films. The films were of high quality. They did not re-dissolve in hexane (as do those formed by dry casting), which is a good solvent for these dots, or in common cleaning solvents such as water, alcohols and acetone. The deposition on both electrodes implies there are both positively and negatively thermally charged dots, unlike conventional electrophoretic deposition. We used simple thermodynamics to explain the results of electrophoretic deposition macroscopically. To connect the macroscopic nature of the deposition to the microscopic nature of the dots we performed electrophoretic mobility measurements of the dots and the results seem to complement the thermodynamic treatment.
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