Abstract
The gaseous product concentration in direct electrochemical CO2 reduction is usually hurdled by the electrode’s Faradaic efficiency, current density, and inevitable mixing with the unreacted CO2. A concentrated gaseous product with high purity will greatly lower the barrier for large-scale CO2 fixation and follow-up industrial usage. Here, we developed a pneumatic trough setup to collect the CO2 reduction product from a precisely engineered nanotwinned electrocatalyst, without using ion-exchange membrane. The silver catalyst’s twin boundary density can be tuned from 0.3 to 1.5 × 104 cm−1. With the lengthy and winding twin boundaries, this catalyst exhibits a Faradaic efficiency up to 92% at −1.0 V and a turnover frequency of 127 s−1 in converting CO2 to CO. Through a tandem electrochemical-CVD system, we successfully produced CO with a volume percentage of up to 52%, and further transformed it into single layer graphene film.
Highlights
The gaseous product concentration in direct electrochemical CO2 reduction is usually hurdled by the electrode’s Faradaic efficiency, current density, and inevitable mixing with the unreacted CO2
The fivefold twinned silver nanowires have been reported to be a prominent catalyst in CO2RR15, and recently study suggests that TB in this kind of silver nanowires shows two orders higher activity than (100) facet of silver nanocubes[16]
As for plate electrodes like metal foils, which are more common in industrial electrosynthesis, it still cannot be fabricated into a gas-diffusion electrode (GDE)
Summary
The gaseous product concentration in direct electrochemical CO2 reduction is usually hurdled by the electrode’s Faradaic efficiency, current density, and inevitable mixing with the unreacted CO2. By channeling the reduced CO stream into a chemical vapor deposition (CVD) system, we could convert the carbon atoms from CO2 into highly value-added single-layer graphene with extraordinary high quality. The pulsed electrochemical deposition was introduced to synthesize highly dense TBs. Under a pulsed current density of 1 A cm−2, the nanotwinned catalyst with the most probable twin width of 10 nm (Nt-10) was prepared.
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