In this study, we
have taken advantage of a pulsed CO
2
electroreduction reaction
(CO
2
RR) approach to tune the
product distribution at industrially relevant current densities in
a gas-fed flow cell. We compared the CO
2
RR selectivity
of Cu catalysts subjected to either potentiostatic conditions (fixed
applied potential of −0.7 V
RHE
) or pulsed electrolysis
conditions (1 s pulses at oxidative potentials ranging from
E
an
= 0.6 to 1.5 V
RHE
, followed by
1 s pulses at −0.7 V
RHE
) and identified the main
parameters responsible for the enhanced product selectivity observed
in the latter case. Herein, two distinct regimes were observed: (i)
for
E
an
= 0.9 V
RHE
we obtained
10% enhanced C
2
product selectivity (FE
C
2
H
4
= 43.6% and FE
C
2
H
5
OH
= 19.8%) in comparison to the potentiostatic CO
2
RR at −0.7 V
RHE
(FE
C
2
H
4
= 40.9% and FE
C
2
H
5
OH
= 11%),
(ii) while for
E
an
= 1.2 V
RHE
, high CH
4
selectivity (FE
CH
4
=
48.3% vs 0.1% at constant −0.7 V
RHE
) was observed.
Operando
spectroscopy (XAS, SERS) and
ex situ
microscopy (SEM and TEM) measurements revealed that these differences
in catalyst selectivity can be ascribed to structural modifications
and local pH effects. The morphological reconstruction of the catalyst
observed after pulsed electrolysis with
E
an
= 0.9 V
RHE
, including the presence of highly defective
interfaces and grain boundaries, was found to play a key role in the
enhancement of the C
2
product formation. In turn, pulsed
electrolysis with
E
an
= 1.2 V
RHE
caused the consumption
of OH
–
species near the catalyst surface, leading
to an OH-poor environment favorable for CH
4
production.