Copper is a unique catalyst for the electrochemical CO2reduction reaction (CO2RR) as it can produce multi-carbon
products,
such as ethylene and propanol. As practical electrolyzers will likely
operate at elevated temperatures, the effect of reaction temperature
on the product distribution and activity of CO2RR on copper is important
to elucidate. In this study, we have performed electrolysis experiments
at different reaction temperatures and potentials. We show that there
are two distinct temperature regimes. From 18 up to ∼48 °C,
C2+ products are produced with higher Faradaic efficiency, while methane
and formic acid selectivity decreases and hydrogen selectivity stays
approximately constant. From 48 to 70 °C, it was found that HER
dominates and the activity of CO2RR decreases. Moreover, the CO2RR
products produced in this higher temperature range are mainly the
C1 products, namely, CO and HCOOH. We argue that CO surface coverage,
local pH, and kinetics play an important role in the lower-temperature
regime, while the second regime appears most likely to be related
to structural changes in the copper surface.