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[Display omitted] • CuBi catalysts were grown on derived copper foam by electrodeposition for CO 2 electroreduction. • Electrodeposition potential significantly affected bimetallic catalyst and CO 2 electroreduction. • The highest formate Faradaic efficiency (FE formate) of 94.4 % was recorded at 38.5 mA/cm2 in a H-type cell. • A higher FE formate of 98.3 % was achieved at 56.6 mA/cm2 in a continuous-flow MEA reactor. Electrochemical reduction of CO 2 to fuels and chemicals is an effective way to reduce greenhouse gas emissions and alleviate the energy crisis, but the highly active catalysts necessary for this reaction under mild conditions are still rare. In this work, we grew CuBi bimetallic catalysts on derived copper foam substrates by co-electrodeposition, and then investigated the correlation between co-electrodeposition potential and electrochemical performance in CO 2 -to-formate conversion. Results showed that the bimetallic catalyst formed at a low potential of − 0.6 V vs. AgCl/Ag electrode achieved the highest formate Faradaic efficiency (FE formate) of 94.4% and a current density of 38.5 mA/cm2 at a low potential of − 0.97 V vs. reversible hydrogen electrode (RHE). Moreover, a continuous-flow membrane electrode assembly reactor also enabled the catalyst to show better performance (a FE formate of 98.3% at 56.6 mA/cm2) than a traditional H-type reaction cell. This work highlights the vital impact of co-electrodeposition potential on catalyst performance and provides a basis for the modulated growth of bimetallic catalysts on substrates. It also shows the possibility of preparing Bi-based catalysts with no obvious decrease in catalytic activity that have been partially replaced with more economic copper. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu 2 O/β-Bi 2 O 3 heterojunction has beautiful flower-like morphology. • The Cu 2 O and β-Bi 2 O 3 phases in Cu-Bi-O/300 are independent. • The Cu 2 O/β-Bi 2 O 3 heterojunction has excellent photo-assisted electrocatalytic CO 2 reduction. • The Cu 2 O/β-Bi 2 O 3 heterojunction can provide lots of active edge sites. CO 2 , as one of the greenhouse gases, actually represents a cheap and abundant C1 fuel to produce fuels and chemical stocks. Herein, inspired by photocatalysis and electrocatalysis, we have successfully synthesized a series of copper and bismuth oxides with heterostructure by a first co-electrodeposition method and then by thermal treatment at different temperatures. The bimetallic oxide (Cu 2 O/β-Bi 2 O 3) at 300 °C with the main exposure of β-Bi 2 O 3 (2 0 1) planes shows the beautiful micro-flower morphology with numerous petals in thickness around 20 ∼ 40 nm. Therefore, the Cu 2 O/β-Bi 2 O 3 heterostructure with active edge sites can electrochemically convert CO 2 into formate with a promising Faradaic efficiency (96.3 %) and current density (40.4 mA cm−2) at − 0.97 V vs. RHE. Specifically, the current density of Cu 2 O/β-Bi 2 O 3 bimetallic catalyst can be largely enhanced to 48.5 mA cm−2 at − 0.92 V vs. RHE with the assistance of light compared to the 30.1 mA cm−2 without light. The production rate of formate with the assistance of light can also be increased to 705.1 μmol h−1 cm−2, superior to that of 536.4 μmol h−1 cm−2 without light. Such an excellent photo-assisted electrochemical CO 2 reduction performance is due to the fast charge-transfer process between Cu 2 O and β-Bi 2 O 3. This study may provide a new route to directly synthesize the photoactive electrocatalysts with more edge sites and heterojunction for promoting electrochemical CO 2 reduction performance with the assistance of light field. [ABSTRACT FROM AUTHOR]

• Bimetallic Bi-Cu electrode was synthesized via co-electroplating strategy. • The synergistic effect of Bi and Cu atoms favors the adsorption of OCHO*. • The superb durability and partial current density toward formate are realized. • KOH and alkaline anion-exchange membrane are beneficial for eCO 2 RR. Tuning the geometric and electronic structure of bimetallic electrocatalyst to facilitate a specific reaction pathway and offer more active sites is a promising avenue for enhancing activity and selectivity of electrocatalytic CO 2 reduction reaction (eCO 2 RR). Owing to formation of Bi-Cu interface through the separated growth of Bi and Cu atoms on defective copper foam, the Bi-Cu bimetallic electrode converts CO 2 to formate with an allured Faradaic efficiency (94.37%) and partial current density (27.85 mA cm−2) at -0.91 Vversus reversible hydrogen electrode (RHE). Notably, such electrode with tight moss-like structure delivers the excellent durability under 58 h electrolysis, outperforming most of the current Bi-based catalysts. Moreover, we have experimentally shown that KOH is a better electrolyte than KHCO 3 due to the lower solution resistance and more confinement of free CO 2 gas, and the alkaline anion-exchange membrane is more ideal than the cation-exchange membrane counterpart, owing to the enhancement of formate selectivity by suppressing the evolution of H 2. This study inspires a complete set of concepts for highly converting CO 2 to formate that contains the design of effective electrocatalysts, the role of growth substrate, the effect of different electrolytes and membranes. [ABSTRACT FROM AUTHOR]

• A nitrogen doped porous carbon cloth (N-CC) is successfully established by calcining the raw carbon cloth with urea. • The N-CC might provide abundant active sites for the nucleation and growth of anchoring nano-sized Cn/Sn (3.39 nm). • The bimetallic copper and tin was simultaneously co-electrodeposited onto the N-CC. • The Cu/Sn electrode could provide abundant active sites for highly coverting CO 2 to formate. The electrochemical CO 2 reduction reaction (CO 2 RR) into liquid fuels is a promising avenue to both store intermittent renewable energy and reduce global CO 2 emission, but daunting bottlenecks owing to poor selectivity, low activity and stability of the electrocatalysts. Herein, we report that bimetallic copper and tin are simultaneously deposited on the nitrogen doped porous carbon cloth (N-CC) via an efficient and facile co-electroplating strategy. The highly conductive N-doped porous carbon cloth as substrate enables a largely uniform distribution of N-doped defects, which can provide more active sites for the nucleation and growth of anchoring nano-sized Cn/Sn (3.39 nm). The as-prepared electrode (Cu (1) Sn (4) -N-CC), with a 3D-hierarchical porous honeycomb structure, could not only favor the diffusion of electrolyte and serve as "transfer posts" to confine the intermediates of reduced CO 2 , but also provide abundant terrace, ledge and kink atoms to function as active site for highly efficient CO 2 RR. As such, the obtained Cu (1) Sn (4) -N-CC electrode convert CO 2 to formate with allured faradic efficiency (90.24 %), partial current density (15.56 mA cm−2) and production rate (173 μmol h-1 cm−2) at −0.97 V RHE , along with a long-term tolerance in CO 2 RR. This study may provide a new design for self-growing bimetallic catalyst on N-doped porous substrate to regulate advanced catalysts/electrodes for different applications. [ABSTRACT FROM AUTHOR]