2.3 Copper based
Copper is one of the few metals that can efficiently convert
CO2 to hydrocarbons such as methane
(CH4) and ethylene
(C2H4), owing to the moderate adsorption
energy of the *CO intermediate.[38,60-61] Because
the electrocatalytic performance of Cu electrodes is usually determined
by the Cu crystal facets, shape control of Cu nanoparticles (NPs) has
been widely studied for desirable CO2RR
selectivity.[62] Zhang et al. synthesized
nanodefective Cu nanosheets using an electrochemical reduction
method.[63] Cu nanosheet electrocatalysts with
defects exhibited a better total current density, maximum ethylene FE of
83.2 % at −1.18 V vs. RHE without CO generation, and partial current
density of up to 66.5 mA cm–2 at −1.48 V vs. RHE,
which is much higher than those of its counterparts (Figure 2(F)–(H)).
Such nanodefective structures promote ethylene production by enhancing
the adsorption of intermediates and hydroxyl ions on the
electrocatalyst.
Recently, simple approaches have been reported for fabricating ultrathin
CuO nanoplate arrays through anodic oxidation for the conversion of
CO2 to
C2H4.[64]Benefitting from stable Cu/Cu2O interfaces, the catalyst
exhibits remarkable C2H4 FE of 84.5 %,
partial current densities of 92.5 mA cm−2 at −0.81 V
vs. RHE, and high stability for 55 h. Yang et al. prepared
one-dimensional ultrathin 5-fold twinned copper NWs for conversion of
CO2 to methane.[65] Corresponding
SEM and transmission electron microscopy (TEM) images revealed ultrathin
NW structures with diameters of ~20 nm. Owing to its
abundant edge sites, Cu NWs showed outstanding CH4selectivity with a maximum FECH4 up to 55 % at −1.25 V
vs. RHE and selectivity.