Continued advancements
in the electrochemical reduction of CO
2
(CO
2
RR) have emphasized that reactivity, selectivity,
and stability are not explicit material properties but combined effects
of the catalyst, double-layer, reaction environment, and system configuration.
These realizations have steadily built upon the foundational work
performed for a broad array of transition metals performed at 5 mA
cm
–2
, which historically guided the research field.
To encompass the changing advancements and mindset within the research
field, an updated baseline at elevated current densities could then
be of value. Here we seek to re-characterize the activity, selectivity,
and stability of the five most utilized transition metal catalysts
for CO
2
RR (Ag, Au, Pd, Sn, and Cu) at elevated reaction
rates through electrochemical operation, physical characterization,
and varied operating parameters to provide a renewed resource and
point of comparison. As a basis, we have employed a common cell architecture,
highly controlled catalyst layer morphologies and thicknesses, and
fixed current densities. Through a dataset of 88 separate experiments,
we provide comparisons between CO-producing catalysts (Ag, Au, and
Pd), highlighting CO-limiting current densities on Au and Pd at 72
and 50 mA cm
–2
, respectively. We further show the
instability of Sn in highly alkaline environments, and the convergence
of product selectivity at elevated current densities for a Cu catalyst
in neutral and alkaline media. Lastly, we reflect upon the use and
limits of reaction rates as a baseline metric by comparing catalytic
selectivity at 10 versus 200 mA cm
–2
. We hope the
collective work provides a resource for researchers setting up CO
2
RR experiments for the first time.
