Anodic Current Research Articles

A N–CoSe/CoSe2–C@Cu hierarchical architecture as a current collector-integrated anode for potassium-ion batteries

The highly reversible insertion/extraction of large-radius K+ into electrode materials remains a tough goal, especially for conversion-type materials. Herein, we design a current collector-integrated electrode (N–CoSe/CoSe2–C@Cu) as an advanced anode for potassium-ion battery (PIBs). The conductive CoSe/CoSe2 heterojunction with rich Se vacancy defects, conductive sp2 N-doped carbon layer, and the elastic copper foil matrix can greatly accelerate the electron transfer and enhance the structural stability. Consequently, the well-designed N–CoSe/CoSe2–C@Cu current collector-integrated electrode displays enhanced potassium storage performance with regard to a high capacity (325.1 mAh·g−1 at 0.1 A·g−1 after 200 cycles), an exceptional rate capability (223.5 mAh·g−1 at 2000 mA·g−1), and an extraordinary long-term cycle stability (a capacity fading of only 0.019% per cycle over 1200 cycles at 2000 mA·g−1). Impressively, ex situ scanning electron microscopy (SEM) characterizations prove that the elastic structure of copper foil is merged into the cleverly designed N–CoSe/CoSe2–C@Cu heterostructure, which buffers the deformation of structure and volume and greatly promotes the cycle life during the potassium/depotassium process.Graphical abstract

Electrocatalytic Reduction of Carbon Dioxide in Acidic Electrolyte with Superior Performance of a Metal-Covalent Organic Framework over Metal-Organic Framework.

CO2 electroreduction (CO2RR) to generate valuable chemicals in acidic electrolytes can improve the carbon utilization rate in comparison to that under alkaline conditions. However, the thermodynamically more favorable hydrogen evolution reaction under an acidic electrolyte makes the CO2RR a big challenge. Herein, robust metal phthalocyanine(Pc)-based (M = Ni, Co) conductive metal-covalent organic frameworks (MCOFs) connected by strong metal tetraaza[14]annulene (TAA) linkage, named NiPc-NiTAA and NiPc-CoTAA, are designed and synthesized to apply in the CO2RR in acidic electrolytes for the first time. The optimal NiPc-NiTAA exhibited an excellent Faradaic efficiency (FECO) of 95.1% and a CO partial current density of 143.0 mA cm-2 at -1.5 V versus the reversible hydrogen electrode in an acidic electrolyte, which is 3.1 times that of the corresponding metal-organic framework NiPc-NiN4. The comparison tests and theoretical calculations reveal that in-plane full π-d conjugation MCOF with a good conductivity of 3.01 × 10-4 S m-1 accelerates migration of the electrons. The NiTAA linkage can tune the electron distribution in the d orbit of metal centers, making the d-band center close to the Fermi level and then activating CO2. Thus, the active sites of NiPc and NiTAA collaborate to reduce the *COOH formation energy barrier, favoring CO production in an acid electrolyte. It is a helpful route for designing outstanding conductive MCOF materials to enhance CO2 electrocatalysis under an acidic electrolyte.

Tetracycline hydrochloride electro- and photo-electrooxidation: a comparative influence study of current density, pollutant concentration, and anode material

Tetracycline hydrochloride electro- and photo-electrooxidation: a comparative influence study of current density, pollutant concentration, and anode material

Mesh GDEs: An alternative to carbon-based electrodes for CO2 reduction at higher current densities

Scaling up the electrolysis of CO2 to multi-carbon products remains a challenge due to the instability of conventional carbon-based gas diffusion materials at higher current densities. In this study, we investigate the use of a CuMesh-Polytetrafluoroethylene (PTFE) sandwich electrode, which is both scalable and can conduct large amounts of current on account of its metallic structure. Although we showcase CO2RR activity up to –500 mA cm−2, the trends we observe indicate this value can be pushed beyond –1 A cm−2. We find that we can achieve a higher ethylene (C2H4) partial current density by increasing mesh sizes (i.e., smaller pores). Furthermore, 100 h durability tests revealed that both morphological changes and reaction-driven electrolyte contamination are critical for steady C2H4 performance even if flooding is mitigated. Thus, substantial room for optimization exists for future works. To conclude, the mesh based GDE we propose herein opens up possibilities for achieving robust industrial-scale CO2 and CO reduction.

Controlling the coverage of intermediates on the active site enables efficient carbon dioxide electroreduction to hydrocarbons

The electrochemical CO2 reduction reaction (ECO2RR) has the capability to convert CO2 molecules into high-value products, offering a feasible pathway aligned with carbon cycling and emission reduction. Nevertheless, significant efforts are required to achieve highly active and selective catalysts tailored for specific products. Herein, a facile synthesis route is proposed, wherein copper, phosphorus, and carbon precursors are mixed and subsequently calcined at different temperatures to obtain a series of copper-based catalysts (CPC-300, 500, 700) containing various copper components with different phases and oxidation states. And further performance tests show their differentiated product distributions. Specifically, CPC-300, which contains more high-valence Cu, is more inclined to produce C2 products, while CPC-700 possessing low-valence Cu as its phase is more keen to produce C1 products. In particular, the CPC-700 catalyst presents a high FECH4 of 52.2 % with a CH4 partial current density of −167.8 mA cm−2 at −1.447 V vs. RHE. Combining the results of in-situ Raman and electrochemical characterizations confirms the effect of valence state and composition on the adsorbed intermediates containing *CO and *H during the reaction. This work achieves the design and development of highly selective and active Cu-based catalysts from the strategies of valence state and component engineering.

Stabilizing Cu0/Cu2+ interface by hydroxy-rich amorphous SiO2 for enhanced electrocatalytic CO2 reduction to ethylene

Constructing a stable Cu0/Cu2+ interface is critical for enhancing the C-C coupling during the process of CO2 electroreduction. However, the high-valence Cu species are unstable under the operating conditions. Herein, polyhedral-shaped CuO is coated with hydroxy-rich SiO2 nanoparticles (m-SiO2/CuO) to stabilize the Cu2+ species, enabling efficient CO2 reduction to the ethylene product. Significantly, the optimal m-SiO2/CuO catalyst exhibits an impressive Faradaic efficiency of 55.5 % and an industrial-level partial current density of 500 mA cm−2 toward ethylene. Fourier transform infrared spectra and X-ray photoelectron spectra reveal that the strong interfacial interaction between CuO and hydroxy-rich SiO2 is conducive to stabilizing the Cu2+ species. In-situ characterizations reveal that the Cu0/Cu2+ interface facilitates CO2 activation and the key intermediate *OCCHO, thus promoting the production of ethylene. This work paves the way for developing advanced electro-catalysts of producing ethylene.

Polyacrylate modified Cu electrode for selective electrochemical CO2 reduction towards multicarbon products

Highly selective production of value-added multicarbon (C2+) products via electrochemical CO2 reduction reaction (eCO2RR) on polycrystalline copper (Cu) remains challenging. Herein, the facile surface modification using poly (α-ethyl cyanoacrylate) (PECA) is presented to greatly enhance the C2+ selectivity for eCO2RR over polycrystalline Cu, with Faradaic efficiency (FE) towards C2+ products increased from 30.1% for the Cu electrode to 72.6% for the obtained Cu-PECA electrode at −1.1 V vs. reversible hydrogen electrode (RHE). Given the well-determined FEs towards C2+ products, the partial current densities for C2+ production could be estimated to be −145.4 mA cm−2 for the Cu-PECA electrode at −0.9 V vs. RHE in a homemade flow cell. In-situ spectral characterizations and theoretical calculations reveal that PECA featured with electron-accepting −C≡N and −COOR groups decorated onto the Cu electrode could inhibit the adsorption of *H intermediates and stabilize the *CO intermediates, given the redistributed interfacial electron density and the raised energy level of d-band center (Ed) of Cu active sites, thus facilitating the C–C coupling and then the C2+ selective production. This study is believed to be guidable to the modification of electrocatalysts and electrodes with polymers to steer the surface adsorption behaviors of reaction intermediates to realize practical eCO2RR towards value-added C2+ products with high activity and selectivity.

Atomically Engineered Encapsulation of SnS2 Nanoribbons by Single-Walled Carbon Nanotubes for High-Efficiency Lithium Storage.

Rechargeable lithium-ion batteries are integral to contemporary energy storage, yet current anode material systems struggle to meet the increasing demand for extended range capabilities. This work introduces a novel composite anode material composed of one-dimensional 2H-phase tin disulfide (SnS2) nanoribbons enclosed within cavities of single-walled carbon nanotubes (SnS2@SWCNTs), achieved through precise atomic engineering. Employing aberration-corrected transmission electron microscopy, we precisely elucidated the crystal structure of SnS2 within the confines of the SWCNTs. This deliberate design effectively addresses the inherent limitations of SnS2 as a lithium-ion anode material, including its low electrical conductivity, considerable volume expansion effects, and unstable solid electrolyte interface membrane. Testing confirmed that SnS2 transforms into the Li5Sn2 alloy phase after full lithiation and back to SnS2 after delithiation, showing excellent reversibility. The composite also benefits from edge effects, improving lithium storage through stronger binding and lower migration barriers, which were supported by calculations. This pioneering work advances high-performance anode materials for applications.

Creation of intrinsic defects on ZIF-8 particles to facilitate electrochemical reduction of CO2 over Fe single-atom catalyst

The fabrication of various defects on the surface of metal single-atom catalysts can improve their electrochemical CO2 reduction reaction (CO2RR) ability, and the current mainstream research focuses on the defect modification of heteroatom doping, while there are fewer studies on intrinsic defects on carbon substrates. Herein, a series of catalysts with both Fe-N4 sites and intrinsic defects were synthesized on the ZIF-8 surface by pyrolytic etching at a suitable temperature under ammonia atmosphere. Electrochemical tests in an H-cell showed that the catalyst achieved CO Faradaic efficiency (FECO) of 96.9 % and CO partial current density (JCO) of 9.088 mA cm−2 at −0.6 V. Through further studies, we introduced a “585” ring structure to describe these intrinsic defects and found that these intrinsic defects on the carbon-based surface can act as active sites to promote CO2RR along with the Fe-N4 sites. This work provides a reference for the study of intrinsic defect-modified single atomic materials.

Designing Bi‐In2O3 Nanoflower Catalysts for Enhanced Performance of Electrochemical CO2 Reduction to Formate

AbstractElectrochemical CO2 reduction (ECO2RR) is capable of converting CO2 into a wide range of value‐added products under relatively mild conditions. Electrocatalyst with high selectivity and activity is crucial for high efficient ECO2RR. Herein, Bi‐In2O3 nanoflower catalysts with different metal ratios synthesized by wet chemical method are used for ECO2RR to produce formate. The results indicate that the hydrogen evolution activity of the Bi‐In2O3 catalysts during ECO2RR is suppressed at a low level and the activity and selectivity of formate production is related to the ratio of Bi to In content in the catalysts. The optimized Bi‐In2O3 catalyst with the ratio of Bi6In94 can achieve a high formate Faradaic efficiency (FEformate) over 80 % under a wide potential range from −0.7 V to −1.2 V vs. RHE, with the maximum value of 88.1 % at −0.7 V vs. RHE. Meanwhile, the highest formate partial current density reaches 47.7 mA cm−2 at −1.2 V vs. RHE and the current density and Faradaic efficiency remain stable during the 10 h stability test. The enhanced formate formation on Bi‐In2O3 NF can be attributed to the synergistic effect between Bi and In according to the characterizations of the Bi‐In2O3 NF.

Facet-switching of rate-determining step on copper in CO2-to-ethylene electroreduction

Reduction of carbon dioxide (CO2) by renewable electricity to produce multicarbon chemicals, such as ethylene (C2H4), continues to be a challenge because of insufficient Faradaic efficiency, low production rates, and complex mechanistic pathways. Here, we report that the rate-determining steps (RDS) on common copper (Cu) surfaces diverge in CO2 electroreduction, leading to distinct catalytic performances. Through a combination of experimental and computational studies, we reveal that C─C bond-making is the RDS on Cu(100), whereas the protonation of *CO with adsorbed water becomes rate-limiting on Cu(111) with a higher energy barrier. On an oxide-derived Cu(100)-dominant Cu catalyst, we reach a high C2H4 Faradaic efficiency of 72%, partial current density of 359 mA cm-2, and long-term stability exceeding 100 h at 500 mA cm-2, greatly outperforming its Cu(111)-rich counterpart. We further demonstrate constant C2H4 selectivity of >60% over 70 h in a membrane electrode assembly electrolyzer with a full-cell energy efficiency of 23.4%.

Sulfite-Assisted Acetate Conversion from CO Electroreduction.

The efficient acetate conversion from CO electroreduction is challenging due to the poor selectivity at high reaction rate, which requires the competition with H2 and other C2+ (i.e., ethylene, ethanol, n-propanol) reduction products. Electrolyte engineering is one of the efficient strategies to regulate the reaction microenvironment. In this work, the adding of sulfite (SO32-) with high nucleophilicity in KOH electrolytes was demonstrated to enable improving the CO-to-acetate conversion via generating a S-O chemical bond between SO32- and oxygenated *C2 intermediates (i.e., *CO-CO, *CO-COH) compared with that in pure KOH system on both synthesized Cu(200)- and normal commercial Cu(111)-facets-exposed metallic Cu catalysts. As a result, the prepared Cu(200)-facets-exposed metallic Cu catalyst with surface ions modification showed an superior Faradaic efficiency of 63.6% at -0.6 A·cm-2, and extraordinary absolute value of peak partial current density as high as 1.52 A·cm-2 with adding SO32- in KOH electrolytes, compared to the best reported values in both CO and CO2 electroreduction. Our work suggests an attractive strategy to introduce the oxyanion with high nucleophilicity in electrolytes to regulate the microenvironment for industrial-current-density electrosynthesis of acetate from CO electroreduction.

Br, O‐Modified Cu(111) Interface Promotes CO2 Reduction to Multicarbon Products

AbstractElectrochemical reduction of CO2 to multicarbon (C2+) products with added value represents a promising strategy for achieving a carbon‐neutral economy. Precise manipulation of the catalytic interface is imperative to control the catalytic selectivity, particularly toward C2+ products. In this study, a unique Cu/UIO‐Br interface is designed, wherein the Cu(111) plane is co‐modified simultaneously by Br and O from UIO‐66‐Br support. Such Cu/UIO‐Br catalytic interface demonstrates a superior Faradaic efficiency of ≈53% for C2+ products (ethanol/ethylene) and the C2+ partial current density reached 24.3 mA cm−2 in an H‐cell electrolyzer. The kinetic isotopic effect test, in situ attenuated total reflection Fourier transform infrared spectroscopy and density functional theory calculations have been conducted to elucidate the catalytic mechanism. The Br, O co‐modification on the Cu(111) interface enhanced the adsorption of CO2 species. The hydrogen‐bond effect from the doped Br atom regulated the kinetic processes of *H species in CO2RR and promoted the formation of *COH intermediate. The formed *COH facilitates the *CO–*COH coupling and promotes the C2+ selectivity finally. This comprehensive investigation not only provides an in‐depth study and understanding of the catalytic process but also offers a promising strategy for designing efficient Cu‐based catalysts with exceptional C2+ products.

Active Oxygenated Structure‐Intensified CO2 Capture Enables Efficient Electrochemical Ethylene Production Over Carbon Nanofibers

AbstractThe pursuit of high efficacy C−C coupling during the electrochemical CO2 reduction reaction remains a tremendous challenge owing to the high energy barrier of CO2 activation and insufficient coverage of the desired intermediates on catalytic sites. Inspired by the concept of capture‐coupled CO2 activation, we fabricated quinone‐grafted carbon nanofibers via an in situ oxidative carbonylation strategy. The quinone functionality of carbon nanofibers promotes the capture of CO2 followed by activation. At a current density of 400 mA cm−2, the Faradaic efficiency of ethylene reached 62.9 %, and a partial current density of 295 mA cm−2 was achieved on the quinone‐rich carbon nanofibers. The results of in situ spectroscopy and theoretical calculations indicated that the remarkable selectivity enhancement in ethylene originates from the quinone structure, rather than the electronic properties of Cu particles. The interaction of quinone with CO2 increases the local *CO coverage and simultaneously hinders the co‐adsorption of *H on Cu sites, which greatly reduces the energy barrier for C−C coupling and restrains subsequent *CO protonation. The modulation strategy involving specific oxygenated structure, as an independent degree of freedom, guides the design of functionalized carbon materials for tailoring the selectivity of desired products during the CO2 capture and reduction.

Active Oxygenated Structure-Intensified CO2 Capture Enables Efficient Electrochemical Ethylene Production Over Carbon Nanofibers.

The pursuit of high efficacy C-C coupling during the electrochemical CO2 reduction reaction remains a tremendous challenge owing to the high energy barrier of CO2 activation and insufficient coverage of the desired intermediates on catalytic sites. Inspired by the concept of capture-coupled CO2 activation, we fabricated quinone-grafted carbon nanofibers via an in situ oxidative carbonylation strategy. The quinone functionality of carbon nanofibers promotes the capture of CO2 followed by activation. At a current density of 400 mA cm-2, the Faradaic efficiency of ethylene reached 62.9 %, and a partial current density of 295 mA cm-2 was achieved on the quinone-rich carbon nanofibers. The results of in situ spectroscopy and theoretical calculations indicated that the remarkable selectivity enhancement in ethylene originates from the quinone structure, rather than the electronic properties of Cu particles. The interaction of quinone with CO2 increases the local *CO coverage and simultaneously hinders the co-adsorption of *H on Cu sites, which greatly reduces the energy barrier for C-C coupling and restrains subsequent *CO protonation. The modulation strategy involving specific oxygenated structure, as an independent degree of freedom, guides the design of functionalized carbon materials for tailoring the selectivity of desired products during the CO2 capture and reduction.

Modulating the Hydrogenation Mechanism of Electrochemical CO2 Reduction Using Ruthenium Atomic Species on Bismuth

AbstractThe conversion of CO2 into formate through electrochemical methods is emerging as an elegant approach for industrial‐scale CO2 utilization in the near future. Although Bismuth (Bi)‐based materials have shown promise thank to their excellent selectivity, their limited reactivity remains a challenge. Herein, this study demonstrates a significant enhancement in the CO2‐to‐formate efficiency of Bi by incorporating ruthenium (Ru) atomic species. Ru single atom doped Bi exhibited a nearly twofold higher partial current density compared with pure Bi and Ru clusters doped Bi, while over 95% Faradaic efficiency (FE) is maintained. Through comprehensive investigations using a combined approach of electrochemical techniques, operando spectroscopy, and theoretical calculations, this study elucidates that the presence of Ru single atom promotes H2O dissociation and H* migration to Bi sites for CO2‐to‐formate conversion by significantly reducing the energy barrier via a H* spillover path. Besides, it is constructed Ru–Bi bridge sites for efficient CO2 hydrogenation via a non‐spillover path, which served as the major mechanism for CO2‐to‐formate conversion in Ru single atom doped Bi.

Reduced Graphene Oxide-Supported SrV4O9 Microflowers with Enhanced Electrochemical Performance for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have received considerable attention in recent years. Anode material is one of the key factors that determine SIBs' electrochemical performance. Current commercial hard carbon anode shows poor rate performance, which greatly limits applications of SIBs. In this study, a novel vanadium-based material, SrV4O9, was proposed as an anode for SIBs, and its Na+ storage properties were studied for the first time. To enhance the electrical conductivity of SrV4O9 material, a microflower structure was designed and reduced graphene oxide (rGO) was introduced as a host to support SrV4O9 microflowers. The microflower structure effectively reduced electron diffusion distance, thus enhancing the electrical conductivity of the SrV4O9 material. The rGO showed excellent flexibility and electrical conductivity, which effectively improved the cycling life and rate performance of the SrV4O9 composite material. As a result, the SrV4O9@rGO composite showed excellent electrochemical performance (a stable capacity of 273.4 mAh g-1 after 200 cycles at 0.2 A g-1 and a high capacity of 120.4 mAh g-1 at 10.0 A g-1), indicating that SrV4O9@rGO composite can be an ideal anode material for SIBs.

Reliability-Based Design Optimization of Additive Manufacturing for Lithium Battery Silicon Anode

Abstract With the blooming of the electric vehicle market and the advancement in the lithium-ion battery industry, silicon anode has shown great potential for the next-generation battery. Using the state-of-the-art additive manufacturing technique (three-dimensional (3D) holographic lithography), researchers have demonstrated that silicon anode can be fabricated as a three-dimensional bicontinuous porous microstructure. However, the volume fluctuation of the silicon anode caused by lithiation during the discharging process causes continuous capacity decay and poor cycling life. Besides, uncertainties are inherent in the manufacturing and usage processes, making it crucial to systematically consider them in the silicon anode design to improve its performance and reliability. To fill the gap between current silicon anode research and future industrial need, this study established a digital twin to investigate the optimal design for silicon anode under the uncertainties of additive manufacturing and battery usage. This study started with developing multiphysics finite element models of the silicon anode lithiation process to investigate the volume fluctuation of silicon. Then, surrogate models were built based on the results from the finite element models to reduce computational cost. The reliability-based design optimization (RBDO) was employed to find the best design point for the silicon anode, in which an outer optimization loop maximized the objective function and an inner loop dedicated to reliability analysis. Finally, the Pareto optimal front of the silicon anode designs was obtained and validated, which shows over 10% improvements in the silicon anode's total capacity and rate capability.

CO2 electrolysis to multi-carbon products in strong acid at ampere-current levels on La-Cu spheres with channels

Achieving satisfactory multi-carbon (C2+) products selectivity and current density under acidic condition is a key issue for practical application of electrochemical CO2 reduction reaction (CO2RR), but is challenging. Herein, we demonstrate that combining microenvironment modulation by porous channel structure and intrinsic catalytic activity enhancement via doping effect could promote efficient CO2RR toward C2+ products in acidic electrolyte (pH ≤ 1). The La-doped Cu hollow sphere with channels exhibits a C2+ products Faradaic efficiency (FE) of 86.2% with a partial current density of −775.8 mA cm−2. CO2 single-pass conversion efficiency for C2+ products can reach 52.8% at −900 mA cm−2. Moreover, the catalyst still maintains a high C2+ FE of 81.3% at −1 A cm−2. The channel structure plays a crucial role in accumulating K+ and OH- species near the catalyst surface and within the channels, which effectively suppresses the undesired hydrogen evolution and promotes C–C coupling. Additionally, the La doping enhances the generation of *CO intermediate, and also facilitates C2+ products formation.

Cu-In Dual Sites with Sulfur Defects toward Superior Ethanol Electrosynthesis from CO2 Electrolysis.

The electrosynthesis of multi-carbon chemicals from excess carbon dioxide (CO2) is an area of great interest for research and commercial applications. However, improving both the yield of CO2-to-ethanol conversion and the stability of the catalyst at the same time is proving to be a challenging issue. Here it is proposed to stabilize active Cu(I) and In dual sites with sulfur defects through an electro-driven intercalation strategy, which leads to the delocalization of electron density that enhances orbital hybridizations between the Cu-C and In-H bonds. Hence, the energy barrier for the rate-limiting *CHO formation step is reduced toward the key *OCHCHO* formation during ethanol production, which is also facilitated by the combined Cu site enabling C-C coupling and In site with a higher oxygen affinity based on both thermodynamic and kinetic calculations. Accordingly, such dual-site catalyst achieves a high partial current density toward ethanol of 409 ± 15mAcm⁻2 for over 120 h. Furthermore, a scaled-up flow cell is assembled with an industrial-relevant current of 5.7 A for over 36 h, in which the carbon loss is less than 2.5% and single-pass carbon efficiency is ≈19%.