Rational design of Cu3PdN nanocrystals for selective electroreduction of carbon dioxide to formic acid

Tailoring vinegar residue-derived all-carbon electrodes for efficient electrocatalytic carbon dioxide reduction to formate through heteroatom doping and defect enrichment

Electrocatalytic carbon dioxide reduction (ECO2R) to formate is the most technically and economically feasible approach to achieve electrochemical CO2 value addition. Here, a few-layer graphene is prepared from vinegar residue. Then a series of heteroatom-doped vertical graphene electrodes (X-rGO, X=P/S/N/B/, NS/NP/NB, NSP/NSB/NPB/NSPB) are prepared. The NS-rGO has improved ECO2R to formate selectivity (Faraday Efficiency (FEHCOO-) = 78.7 %) thanks to the synergistic effect between N and S. Carbon quantum dots (CQDs) are introduced into the electrode, the doped heteroatoms are further removed by high-temperature to form the defects-rich electrode (NS-CQDs-rGO-1100), which has better catalytic performance (FEHCOO-=90 %, stability over 10 h) with electrochemical double layer capacitance of 12.5 mF cm-2. The intrinsic effect of heteroatom doping and defects on the ECO2R activity of the electrodes are explored by density functional theory calculation. This work broadens the field of preparation of graphene and opens the door to the development of cost-effective electrocatalysts for efficient ECO2R.

Recent advancements in carbon/metal-based nano-catalysts for the reduction of CO2 to value-added products

Due to the increased human activities in burning of fossil fuels and deforestation, the CO2 level in the atmosphere gets increased up to 415 ppm; although it is an essential component for plant growth, an increased level of CO2 in the atmosphere leads to global warming and catastrophic climate change. Various conventional methods are used to capture and utilize CO2, among that a feasible and eco-friendly technique for creating value-added products is the CO2RR. Photochemical, electrochemical, thermochemical, and biochemical approaches can be used to decrease the level of CO2 in the atmosphere. The introduction of nano-catalysts in the reduction process helps in the efficient conversion of CO2 with improved selectivity, increased efficiency, and also enhanced stability of the catalyst materials. Thus, in this mini-review of nano-catalysts, some of the products formed during the reduction process, like CH3OH, C2H5OH, CO, HCOOH, and CH4, are explained. Among different types of metal catalysts, carbonaceous, single-atom catalysts, and MOF based catalysts play a significant role in the CO2 RR process. The effects of the catalyst material on the surface area, composition, and structural alterations are covered in depth. To aid in the design and development of high-performance nano-catalysts for value-added products, the current state, difficulties, and future prospects are provided.

A dendritic porous copper foam-carbonic anhydrase biohybrid for carbon dioxide electroreduction

Carbonic anhydrase (CA) is bound to a dendritic porous copper foam (3D-Cu) via electrostatic interaction to form a biohybrid (CA/3D-Cu), which exhibits high selectivity and Faraday efficiency in the electroreduction of carbon dioxide (CO2) to formic acid (selectivity of 98.7%, Faraday efficiency of 82.1%) due to the large specific surface area of the 3D-Cu and the ultra-high CO2 hydration capacity of CA.

Metal-Oxide Heterojunction: From Material Process to Neuromorphic Applications

As technologies like the Internet, artificial intelligence, and big data evolve at a rapid pace, computer architecture is transitioning from compute-intensive to memory-intensive. However, traditional von Neumann architectures encounter bottlenecks in addressing modern computational challenges. The emulation of the behaviors of a synapse at the device level by ionic/electronic devices has shown promising potential in future neural-inspired and compact artificial intelligence systems. To address these issues, this review thoroughly investigates the recent progress in metal-oxide heterostructures for neuromorphic applications. These heterostructures not only offer low power consumption and high stability but also possess optimized electrical characteristics via interface engineering. The paper first outlines various synthesis methods for metal oxides and then summarizes the neuromorphic devices using these materials and their heterostructures. More importantly, we review the emerging multifunctional applications, including neuromorphic vision, touch, and pain systems. Finally, we summarize the future prospects of neuromorphic devices with metal-oxide heterostructures and list the current challenges while offering potential solutions. This review provides insights into the design and construction of metal-oxide devices and their applications for neuromorphic systems.

Investigation of the Mechanisms of CO2/O2 Adsorption Selectivity on Carbon Materials Enhanced by Oxygen Functional Groups

Power plant flue gas and industrial waste gas are produced in large quantities. Using these as feedstocks for CO2 electroreduction has important practical significance for the treatment of excessive CO2 emissions. However, O2 in such sources strongly inhibits the electrochemical conversion of CO2. The inhibitory effect of O2 can be mitigated by constructing CO2-enriched regions on the surface of the cathode. In this study, the reaction zone was controlled by the selective adsorption of CO2 on oxygen-functionalized carbon materials. The results of quantum chemical simulations showed that CO2 adsorption was mainly influenced by electrostatic interactions, whereas O2 adsorption was completely regulated by dispersion interactions. This distinction indicated that introducing polar oxygen functional groups at the edge of the carbon plane can significantly enhance the selectivity for CO2/O2 adsorption. The difference in the adsorption energy between CO2 and O2 increased most noticeably after the carboxyl groups were introduced. The results of the adsorption experiments showed that oxygen-functionalization increased the CO2/O2 selectivity of the carbon material under an atmosphere of multicomponent gases by more than 4.9 times. The carboxyl groups played a dominant role. Our findings might act as a reference for the selective adsorption of polar molecules over nonpolar molecules.

Regulating charge distribution of Cu3PdN nanocrystals for nitrate electroreduction to ammonia

As-synthesized Cu3PdN nanocrystals displayed high faradaic efficiency and selectivity for nitrate-to-ammonia conversion. The excellent performances can be attributed to the charge redistribution in Cu3PdN as a result of modulations of the electronic structures of Pd and Cu atoms, which altered the adsorption activation energy of the intermediates during the nitrate reduction reaction process.

Honeycomb-like CuO@C for electroreduction of carbon dioxide to ethylene

The electrochemical CO₂ reduction (ECR) of high-value multicarbon products is an urgent challenge for catalysis and energy resources. Herein, we reported a simple polymer thermal treatment strategy for preparing honeycomb-like CuO@C catalysts for ECR with remarkable C₂H₄ activity and selectivity. The honeycomb-like structure favored the enrichment of more CO₂ molecules to improve the CO₂-to-C₂H₄ conversion. Further experimental results indicate that the CuO loaded on amorphous carbon with a calcination temperature of 600 °C (CuO@C-600) has a Faradaic efficiency (FE) as high as 60.2% towards C₂H₄ formation, significantly outperforming pure CuO-600 (18.3%), CuO@C-500 (45.1%) and CuO@C-700 (41.4%), respectively. The interaction between the CuO nanoparticles and amorphous carbon improves the electron transfer and accelerates the ECR process. Furthermore, in situ Raman spectra demonstrated that CuO@C-600 can adsorb more adsorbed *CO intermediates, which enriches the CC coupling kinetics and promotes C₂H₄ production. This finding may offer a paradigm to design high-efficiency electrocatalysts, which can be beneficial to achieve the "double carbon goal."

Alloying strategies for tuning product selectivity during electrochemical CO2 reduction over Cu

Excessive reliance on fossil fuels has led to the release and accumulation of large quantities of CO₂ into the atmosphere which has raised serious concerns related to environmental pollution and global warming. One way to mitigate this problem is to electrochemically recycle CO₂ to value-added chemicals or fuels using electricity from renewable energy sources. Cu is the only metallic electrocatalyst that has been shown to produce a wide range of industrially important chemicals at appreciable rates. However, low product selectivity is a fundamental issue limiting commercial applications of electrochemical CO₂ reduction over Cu catalysts. Combining copper with other metals that actively contribute to the electrochemical CO₂ reduction reaction process can selectively facilitate generation of desirable products. Alloying Cu can alter surface binding strength through electronic and geometric effects, enhancing the availability of surface confined carbon species, and stabilising key reduction intermediates. As a result, significant research has been undertaken to design and fabricate copper-based alloy catalysts with structures that can enhance the selectivity of targeted products. In this article, progress with use of alloying strategies for development of Cu-alloy catalysts are reviewed. Challenges in achieving high selectivity and possible future directions for development of new copper-based alloy catalysts are considered.

Lattice-dislocated Bi nanosheets for electrocatalytic reduction of carbon dioxide to formate over a wide potential window

Electrochemical reduction of CO₂ to HCOOH (ERC-HCOOH) is one of the most feasible and economically valuable ways to achieve carbon neutrality. Unfortunately, achieving optimal activity and selectivity for ERC-HCOOH remains a challenge. Herein, ultrathin Bi nanosheets (NS) with lattice dislocations (LD-Bi) were prepared by the topological transformation of Bi₂O₂CO₃ NS under high current conditions. LD-Bi exhibited excellent activity and selectivity as well as stability in ERC-HCOOH. Electrochemical tests and DFT calculations revealed that the excellent performance of LD-Bi was attributed to lattice dislocations, which can induce the production of more active sites on the catalyst surface and improve the electronic transfer ability. In addition, LD-Bi was beneficial to enhance the adsorption of CO₂ and key reaction intermediates (OCHO*), thus improving the reaction kinetics. The result provides a unique perspective on the crucial role of lattice dislocations, which may have a significant impact on highly selective electrochemical conversion of CO₂.

Controlled assembly of nitrogen-doped iron carbide nanoparticles on reduced graphene oxide for electrochemical reduction of carbon dioxide to syngas

The electrocatalytic CO₂ reduction reaction (CO₂RR) decreases the amount of greenhouse gas in the atmosphere while enabling a closed carbon cycle. Herein, iron oleate was used as a precursor to produce oleic acid-coated triiron tetraoxide nanoparticles (Fe₃O₄@OA NPs) by pyrolysis, which was then assembled with reduced graphene oxide (rGO) and doped with dicyandiamide as a nitrogen source to obtain nitrogen-doped iron carbide nanoparticles assembled on rGO (N-Fe₃C/rGO NPs). The catalyst prepared by nitrogen doping at 800 °C with an Fe₃O₄@OA NPs to rGO weight ratio of 20:1 showed good activity and stability for the CO₂RR. At -0.3 to -0.4 V, the H₂/CO ratio of the product from the catalyzed CO₂RR was close to 2; thus, the product can be used for Fischer-Tropsch synthesis. The results of a series of experiments and X-ray photoelectron spectroscopy analysis showed that the synergy between the CN and FeN groups in the catalyst can promote the reduction of CO₂ to CO. This work demonstrates a facile method for improving the catalytic reduction of CO₂.