Human activities during the last century have increased the concentration of greenhouse gases in Earth's atmosphere, mainly carbon dioxide (CO2), and the impacts of climate change around the world ...are becoming more damaging. Therefore, scientific research is needed to mitigate the consequences of atmospheric CO2, and, among others, the electrochemical CO2 conversion to useful chemicals is one of the most interesting alternatives. Herein, different Bi, Sn and Sb systems were synthesised as nanoparticles, supported on carbon (Vulcan XC‐72R) and finally used to manufacture electrodes. The Bi−Sn−Sb nanoparticulated systems and their corresponding electrodes were characterised by TEM, XPS, ICP‐OES and SEM. Electrochemical reduction of CO2 to formate was performed in an electrochemical H‐type cell in a CO2‐saturated KHCO3 and KCl solution. The Bi−Sn−Sb electrodes exhibited good activity and selectivity for the CO2 reduction towards formate. Particularly, Bi95Sb05/C and Bi80Sn10Sb10/C electrodes showed improved stability compared to previous works, keeping values of formate efficiency over 50 % after 24 h.
Carbon‐supported Bi−Sn−Sb nanoparticles were prepared, characterized, and used for the electrocatalytic reduction of CO2 to formate. Results indicate that Bi95Sb05/C and Bi80Sn10Sb10/C electrodes displayed an optimal trade‐off in terms of activity, selectivity, and stability under working conditions. Interestingly, the incorporation of small quantities of Sb and Sn to Bi significantly enhanced its stability without substantially affecting its activity and selectivity.
Bismuth is a catalyst material that selectively produces formate during the electrochemical reduction of CO2. While different synthesis strategies have been employed to create electrocatalysts with ...better performance, the restructuring of bismuth precatalysts during the reaction has also been previously reported. The mechanism behind the change has, however, remained unclear. Here, we show that Bi2O3 nanoparticles supported on Vulcan carbon intrinsically transform into stellated nanosheet aggregates upon exposure to an electrolyte. Liquid cell transmission electron microscopy observations first revealed the gradual restructuring of the nanoparticles into nanosheets in the presence of 0.1 M KHCO3 without an applied potential. Our experiments also associated the restructuring with solubility of bismuth in the electrolyte. While the consequent agglomerates were stable under moderate negative potentials (−0.3 VRHE), they dissolved over time at larger negative potentials (−0.4 and −0.5 VRHE). Operando Raman spectra collected during the reaction showed that under an applied potential, the oxide particles reduced to metallic bismuth, thereby confirming the metal as the working phase for producing formate. These results inform us about the working morphology of these electrocatalysts and their formation and degradation mechanisms.
Herein, the electrochemical reduction of CO2 to formate on carbon-supported bismuth nanoparticles is reported. Carbon-supported Bi nanoparticles (about 10 nm in size) were synthesized using a simple, ...fast and scalable approach performed under room conditions. The so-prepared Bi electrocatalyst was characterized by different physicochemical techniques, including transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction and subsequently air-brushed on a carbon paper to prepare electrodes. These electrodes were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy and also by cyclic voltammetry. Finally, CO2 electroreduction electrolyses were performed at different electrode potentials for 3 h. At the optimal electrode potential (−1.6 V vs AgCl/Ag), the concentration of formate was about 77 mM with a faradaic efficiency of 93 ± 2.5%. A 100% faradaic efficiency was found at a lower potential (−1.5 V vs AgCl/Ag) with a formate concentration of about 55 mM. In terms of stability, we observed that after about 70 h (in 3 h electrolysis experiments at different potentials), the electrode deactivates due to the gradual loss of metal as shown by SEM/EDX analyses of the deactivated electrodes.
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•Bi-based catalysts were used in a continuous process for CO2 electroreduction.•The process developed offers the best trade-off among relevant figures of merit.•FE of 90% and ...concentrations of 340 g·L−1 of HCOO− were achieved.•At 45 mA·cm−2, energy consumption of only 180 kWh·kmol−1 was required.
The electrochemical conversion of CO2 is gaining increasing attention because it could be considered as an appealing strategy for making value-added products at mild conditions from CO2 captured. In this work, we report a process for the electrocatalytic reduction of CO2 to formate (HCOO−) operating in a continuous way, employing a single pass of the reactants through the electrochemical reactor and using Bi carbon supported nanoparticles in the form of a membrane electrode assembly composed by a Gas Diffusion Electrode, a current collector and a cationic exchange membrane. This contribution presents the best trade-off between HCOO− concentration, Faradaic Efficiency and energy consumption in the literature. We also show noteworthy values of energy consumption required of only 180 kWh·kmol−1 of HCOO−, lower than previous approaches, working at current densities that allow achieving formate concentration higher than 300 g·L−1 and simultaneously, a Faradaic Efficiency close to 90%. The results here displayed make the electrochemical approach closer for future implementation at the industrial scale.
The development of new electrocatalysts with improved properties for the electrochemical reduction of CO2 is being the objective of innumerable contributions. In this contribution, the ...electrochemical reduction of CO2 to formate on novel carbon-supported antimony nanoparticles (Sb/C NPs) is studied. The carbon-supported Sb2O3/Sb nanoparticles were synthesised using a simple methodology at room temperature and characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The Sb2O3/Sb/C electrodes were prepared by air-brushed onto a carbon paper and were characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The Sb2O3/Sb/C electrodes were also electrochemically characterized by cyclic voltammetry and displayed a clear activity for CO2 electroreduction. To evaluate the properties of the electrodes for the reduction of CO2, electrolyses at different potentials were systematically conducted. Hydrogen and formate were the only products found. The faradic efficiency towards formate was found to be about 20%. This FE was in good agreement with previous finding obtained with comparable system. Interestingly, 24-hour tests were carried out to analyse the stability of the material under working conditions. The results indicate that Sb2O3/Sb-based electrodes display a remarkably better stability than other nanostructured electrocatalysts such as Sn or Bi.
The combination of compositional versatility and topological diversity for the integration of electroactive species into high-porosity molecular architectures is perhaps one of the main appeals of ...metal–organic frameworks (MOFs) in the field of electrocatalysis. This premise has attracted much interest in recent years, and the results generated have also revealed one of the main limitations of molecular materials in this context: low stability under electrocatalytic conditions. Using zirconium MOFs as a starting point, in this work, we use this stability as a variable to discriminate between the most suitable electrocatalytic reaction and specific topologies within this family. Our results revealed that the PCN-224 family is particularly suitable for the electroreduction of molecular nitrogen for the formation of ammonia with faradaic efficiencies above 30% in the presence of Ni2+ sites, an activity that improves most of the catalysts described. We also introduce the fluorination of porphyrin at the meso position as a good alternative to improve both the activity and stability of this material under electrocatalytic conditions.
Electrochemical conversion of CO2 into formic acid (FA) in an aqueous electrolyte is considered a promising strategy to valorise waste-CO2. Some studies, mainly performed using Sn cathodes, have ...shown that the performance of the process can be strongly improved using pressurized systems. On the other hand, other studies, usually carried out in non-pressurized systems, have indicated that the nature of the cathode can strongly affect the process. Hence, in this work, we have investigated the coupled effect of nature of the cathode and CO2 pressure (PCO2) on the electrochemical conversion of CO2 to FA. Four electrodes (Sn, Sn/C-NP, Bi, Bi/C-NP) have been used as model cathodes. The results obtained have shown that the increase of PCO2 enhances the production of FA and the faradic efficiency of the process (FEFA) for all tested cathodes. Moreover, it has been observed that nanoparticle-based cathodes provided better results for electrolyses carried out at 1 bar and high current density. Conversely, at relatively high PCO2, the effect of the nature of the cathode becomes less important and bulk Sn and Bi electrodes display very interesting results in terms of production of FA, FEFA and stability.
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Bismuth is a catalyst material that selectively produces formate during the electrochemical reduction of CO
. While different synthesis strategies have been employed to create electrocatalysts with ...better performance, the restructuring of bismuth precatalysts during the reaction has also been previously reported. The mechanism behind the change has, however, remained unclear. Here, we show that Bi
O
nanoparticles supported on Vulcan carbon intrinsically transform into stellated nanosheet aggregates upon exposure to an electrolyte. Liquid cell transmission electron microscopy observations first revealed the gradual restructuring of the nanoparticles into nanosheets in the presence of 0.1 M KHCO
without an applied potential. Our experiments also associated the restructuring with solubility of bismuth in the electrolyte. While the consequent agglomerates were stable under moderate negative potentials (-0.3 V
), they dissolved over time at larger negative potentials (-0.4 and -0.5 V
).
Raman spectra collected during the reaction showed that under an applied potential, the oxide particles reduced to metallic bismuth, thereby confirming the metal as the working phase for producing formate. These results inform us about the working morphology of these electrocatalysts and their formation and degradation mechanisms.
Electrochemical reduction of carbon dioxide (CO2) into green fuels and valuable chemicals is an up-and-coming method of CO2 valorization. Formate/formic acid is one the most desirable product among ...the many other possible chemicals that can be generated from CO2. Herein, we report on a simple and tunable method to prepare Bi-based electrocatalyst. An affordable metal-organic framework (MOF) precursor TAL-33 has been utilized upon carbonization. This MOF was fabricated from a novel modular carbon-rich ligand 1H-benzodimidazole-5,6-diol and bismuth chloride. Cyclic voltammetry and chronoamperometric measurements were performed to investigate the electrocatalytic activity and selectivity towards the formate. The most promising samples have shown high Faradaic efficiency and stability. The in-depth physical characterization of catalyst structure (XPS, XRD, SEM, and TEM) was performed to investigate the structure-activity relationships. Theoretical studies have been performed to confirm that the enhanced CO2 electroreduction to formate is linked to the presence of metallic bismuth sites.
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•The carbon-rich linker ensured formation of metallic bismuth sites after carbonization at 600 ºC.•Bi-based catalysts were tested for CO2 electroreduction to formate.•Theoretical modeling has confirmed positive effect of metallic bismuth active sites.
The combination of compositional versatility and topological diversity for the integration of electroactive species into high-porosity molecular architectures is perhaps one of the main appeals of ...metal-organic frameworks (MOFs) in the field of electrocatalysis. This premise has attracted much interest in recent years, and the results generated have also revealed one of the main limitations of molecular materials in this context: low stability under electrocatalytic conditions. Using zirconium MOFs as a starting point, in this work, we use this stability as a variable to discriminate between the most suitable electrocatalytic reaction and specific topologies within this family. Our results revealed that the PCN-224 family is particularly suitable for the electroreduction of molecular nitrogen for the formation of ammonia with faradaic efficiencies above 30% in the presence of Ni
sites, an activity that improves most of the catalysts described. We also introduce the fluorination of porphyrin at the
position as a good alternative to improve both the activity and stability of this material under electrocatalytic conditions.
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