Fast Electron Transfer Research Articles

Synergistic Co/S co-doped CeO2 sulfur-oxide catalyst for efficient catalytic reduction of toxic organics and heavy metal pollutants under dark conditions

The rising accumulation of pollutants, including heavy metals and toxic organics, necessitates effective environmental remediation to protect health and biological systems. In this study, a cubic cerianite CeO2-like Co/S co-doped CeO2 sulfur-oxide catalyst (labeled as CeCoOS) with super catalytic reduction performance of pollutants with NaBH4 as a reducing agent under dark was prepared via a green and facile preparation method. Transition metal Co2+-cation and S2−-anion co-doped CeO2 adjusted the energy bandgap and introduced oxygen vacancy (Vo), which converted Ce4+ around Vo into Ce3+ to maintain electric neutrality. The heterovalent Ce4+/Ce3+ states in Co/S-CeO2 enhance the electron lifetime and facilitate fast electron transfer. The valence transition between Ce4+/Ce3+ and Vo make the Co/S co-doped in CeO2 catalyst increase its electrochemically active surface sites and accelerate the pollutants reduction reaction. The CeCoOS-3 with Co/S dopants has an excellent catalytic reduction activity to completely reduce 20 ppm toxic 4-NP in 10 min, 50 ppm organic dyes of MB, RhB, and MO in 6 min, and 50 ppm heavy metal Cr6+ in 10 min. The CeCoOS-3 sulfur-oxide catalyst also exhibited excellent stability in the reusability test. Therefore, CeCoOS sulfur-oxide catalysts are expected to be used for dye decolorization, detoxification of organic toxins, and reduction of electroplating wastewater.

Single‐Atom Immobilization Boosting Oxygen Redox Kinetics of High‐Entropy Perovskite Oxide Toward High‐Performance Lithium‐Oxygen Batteries

AbstractUnderstanding and modulating the unique electronic interaction between single‐metal atoms and high entropy compounds are of great significance to enable their high‐efficiency oxygen electrocatalysis for aprotic lithium‐oxygen (Li‐O2) batteries. Herein, a novel bi‐functional electrocatalyst is for the first time created by immobilizing single‐atom ruthenium (Ru) on lanthanum‐based high entropy perovskite oxide La(Mn0.2Co0.2Fe0.2Ni0.2Cr0.2)O3 (Ru@HEPO), which demonstrates high activity and stability in Li‐O2 batteries. The heteronuclear coordination between single‐atom Ru and HEPO facilitates fast electron transfer from Ru to HEPO by establishing Ru‐O‐M (M stands for Mn, Co, Fe, Ni) bridges, which well redistributes electrons within the Ru@HEPO hence significantly improving its interfacial charge transfer kinetics and electrocatalytic activity. Additionally, the strong electron coupling between Ru and Mn atoms enhances the hybridization between Mn 3d and O 2p orbitals, which promotes the inherent affinity of Ru@HEPO toward the LiO2 intermediate, thereby reducing the reaction energy barrier of the oxygen electrode. As a result, the Ru@HEPO‐based Li‐O2 batteries deliver remarkable electrochemical performances, such as high energy efficiency (87.3% at 100 mA g−1), excellent rate capability (low overpotential of 0.52 V at 100 mA g−1) and durable cyclability (345 cycles at 300 mA g−1). This work opens up a promising avenue for the development of high entropy‐based electrocatalysts for Li‐O2 batteries by precisely tailoring the electronic distributions at an atomic scale.

Mechanochemical nitridation of micron zero-valent iron for enhanced dechlorination of trichloroethylene: Mechanistic insights into nitrogen sources and ball milling conditions

The performance optimization of zero-valent iron (ZVI) based materials for reductive dechlorination remains challenging. After extensive research on sulfidation modification, the doping of heteroatom nitrogen (N) into ZVI for reductive dechlorination of chlorinated hydrocarbons (CHCs) becomes a new promising trend. In this study, surface modification of microscale ZVI (mZVI) was carried out by a facile ball milling method, and Fe–N(C) coated mZVI (abbreviated as N(C)-mZVIbm) synthesized from different N sources of dimethylimidazole, urea and melamine were characterized. The effects of nitrogen-to-iron ratios (N/Fe), ball milling time and speed on the reductive dechlorination of trichloroethylene (TCE) were further investigated. A series of characterization and mechanistic analysis showed that the high reactivity of N(C)-mZVIbm with melamine as nitrogen source (abbreviated as N(C)-mZVIbm(M)) was attributed to the properties and thickness of its particle passivation layer, and faster electron transfer from the reduced iron species to the surface layer. In addition, N(C)-mZVIbm(M) exhibited great performance for dechlorination at a wide pH range of 3 to 11, due to alleviated passivation of the Fe0 core under alkaline conditions by Fe–N(C). This study presents new ideas and evidences for the environmentally friendly synthesis of N-modified ZVI materials and their practical application in groundwater remediation.

A Metal-Free Triazacoronene-Based Bimodal VOC Sensor.

Developing suitable sensors for selective and sensitive detection of volatile organic compounds (VOCs) is crucial for monitoring indoor and outdoor air quality. VOCs are very harmful to our health upon inhalation or contact. Bimodal sensor materials with more than one transduction capability (optical and electrical) offer the ability to extract complementary information from the individual analyte, thus improving detection accuracy and performance. The privilege of manipulating the optoelectronic properties of the polycyclic aromatic hydrocarbon-based semiconducting materials offers rapid signal transduction in multimodal sensing applications. A thiophene-functionalized triazacoronene (TTAC) donor-acceptor-donor (D-A-D) type sensor is reported here for VOC sensing. The single-crystal X-ray structure analysis of the TTAC revealed that a distinctive supramolecular polymer architecture was formed because of cooperative π-π and intermolecular D-A interactions and exhibited rapid signal transduction upon exposure to specific VOCs. The TTAC-embedded green luminescent paper-based test strip exhibited an on-off fluorescence response upon nitrobenzene vapor exposure for 120 s. The selective and rapid response is due to the fast photoinduced electron transfer, as is evident from the time-resolved excited-state dynamics and density functional theory studies. The thick-film-based prototype chemiresistive sensor detects harmful VOCs in a custom-made gas sensing system including benzene, toluene, and nitrobenzene. The TTAC sensor rapidly responds (200 s) at relatively low temperatures (180 οC) compared to other reported metal-oxide-based sensors.

Development of an inexpensive poly(MO)/CNT@PGE for voltammetric investigation of Methocarbamol in presence of Levofloxacin

This work describes the voltammetric investigation of trace amounts of pain reliever drug methocarbamol (MET) by carbon nanotubes decorated methyl orange polymerized pencil graphite electrode (poly(MO)/CNT@PGE). The proposed modified electrode was prepared by electropolymerization of methyl orange (MO) over the carbon nanotubes (CNTs) decorated on PGE. The geomorphologies of the equipped sensors were accomplished by scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) and electrochemical impedance spectroscopy (EIS) study. The electrochemical behaviour of MET in presence of levofloxacin (LVF) has been studied by applying different voltammetric techniques in 0.1 M PBS of pH 4.0. The proposed poly(MO)/CNT@PGE shows enhanced peak current with a small negative shift in peak potential for MET over the bare and modified electrodes due to the electrocatalytic features of the modifiers. The different parameters such as effect of polymer layers, pH, scan rate, concentrations, simultaneous and selectivity study for MET were studied by cyclic voltammetry (CV), linear sweep voltammetry (LSV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). The computed limit of detection (LOD) for MET at different concentrations (10.0–110.0 µM for DPV and 1.0–12.0 µM for SWV) was found to be 5.24 µM and 0.69 µM, respectively. The adapted electrode exhibits special characteristic features such as stability, repeatability, reproducibility, fast electron transfer behaviour and charge transfer resistance (Rct). Based on the results obtained, number of electrons (n), number of protons (m), heterogeneous rate constant (ko) and surface concentration (Γ0) of MET have been calculated by using relative formulae. The selectivity and applicability of the modified electrode were premeditated by real sample investigation of MET present in pharmaceutical tablets with good recovery results to confirm the analytical pertinence of the proposed sensor.

Non-Faradaic optoelectrodes for safe electrical neuromodulation

Nanoscale optoelectrodes hold the potential to stimulate optically individual neurons and intracellular organelles, a challenge that demands both a high-density of photoelectron storage and significant charge injection. Here, we report that zinc porphyrin, commonly used in dye-sensitized solar cells, can be self-assembled into nanorods and then coated by TiO2. The J-aggregated zinc porphyrin array enables long-range exciton diffusion and allows for fast electron transfer into TiO2. The formation of TiO2(e−) attracts positive charges around the neuron membrane, contributing to the induction of action potentials. Far-field cranial irradiation of the motor cortex using a 670 nm laser or an 850 nm femtosecond laser can modulate local neuronal firing and trigger motor responses in the hind limb of mice. The pulsed photoelectrical stimulation of neurons in the subthalamic nucleus alleviates parkinsonian symptoms in mice, improving abnormal stepping and enhancing the activity of dopaminergic neurons. Our results suggest injectable nanoscopic optoelectrodes for optical neuromodulation with high efficiency and negligible side effects.

Protein-Aided Synthesis of Copper-Integrated Polyaniline Nanocomposite Encapsulated with Reduced Graphene Oxide for Highly Sensitive Electrochemical Detection of Dimetridazole in Real Samples.

Dimetridazole (DMZ) is a derivative of nitroimidazole and is a veterinary drug used as an antibiotic to treat bacterial or protozoal infections in poultry. The residues of DMZ cause harmful side effects in human beings. Thus, we have constructed a superior electrocatalyst for DMZ detection. A copper (Cu)-integrated poly(aniline) (PANI) electrocatalyst (PANI-Cu@BSA) was prepared by using a one-step method of biomimetic mineralization and polymerization using bovine serum albumin (BSA) as a stabilizer. Then, the synthesized PANI-Cu@BSA was encapsulated with reduced graphene oxide (rGO) using an ultrasonication method. The PANI-Cu@BSA/rGO nanocomposite had superior water dispersibility, high electrical conductivity, and nanoscale particles. Moreover, a PANI-Cu@BSA/rGO nanocomposite-modified, screen-printed carbon electrode was used for the sensitive electrochemical detection of DMZ. In phosphate buffer solution, the PANI-Cu@BSA/rGO/SPCE displayed a current intensity greater than PANI-Cu@BSA/SPCE, rGO/SPCE, and bare SPCE. This is because PANI-Cu@BSA combined with rGO increases fast electron transfer between the electrode and analyte, and this synergy results in analyte-electrode junctions with extraordinary conductivity and active surface areas. PANI-Cu@BSA/rGO/SPCE had a low detection limit, a high sensitivity, and a linear range of 1.78 nM, 5.96 μA μM-1 cm-2, and 0.79 to 2057 μM, respectively. The selective examination of DMZ was achieved with interfering molecules, and the PANI-Cu@BSA/rGO/SPCE showed excellent selectivity, stability, repeatability, and practicability.

Electron transfer rate modulation with mid-IR in butadiyne-bridged donor-bridge-acceptor compounds.

Controlling electron transfer (ET) processes in donor-bridge-acceptor (DBA) compounds by mid-IR excitation can enhance our understanding of the ET dynamics and may find practical applications in molecular sensing and molecular-scale electronics. Alkyne moieties are attractive to serve as ET bridges, as they offer the possibility of fast ET and present convenient vibrational modes to perturb the ET dynamics. Yet, these bridges introduce complexity because of the strong torsion angle dependence of the ET rates and transition dipoles among electronic states and a shallow torsion barrier. In this study, we implemented ultrafast 3-pulse laser spectroscopy to investigate how the ET from the dimethyl aniline (D) electron donor to the N-isopropyl-1,8-napthalimide (NAP) electron acceptor can be altered by exciting the CC stretching mode (νCC) of the butadiyne bridge linking the donor and acceptor. The electron transfer was initiated by electronically exciting the acceptor moiety at 400 nm, followed by vibrational excitation of the alkyne, νCC, and detecting the changes in the absorption spectrum in the visible spectral region. The experiments were performed at different delay times t1 and t2, which are the delays between UV-mid-IR and mid-IR-Vis pulses, respectively. Two sets of torsion-angle conformers were identified, one featuring a very fast mean ET time of 0.63 ps (group A) and another featuring a slower mean ET time of 4.3 ps (group B), in the absence of the mid-IR excitation. TD-DFT calculations were performed to determine key torsion angle dependent molecular parameters, including the electronic and vibrational transition dipoles, transition frequencies, and electronic couplings. To describe the 3-pulse data, we developed a kinetic model that includes a locally excited, acceptor-based S2 state, a charge separated S1 state, and their vibrationally excited counterparts, with either excited νCC (denoted as S1Atr, S1Btr, S2Atr, and S2Btr, where tr stands for the excited triplet bond, νCC) or excited daughter modes of the νCC relaxation (S1Ah, S1Bh, S2Ah, and S2Bh, where h stands for vibrationally hot species). The kinetic model was solved analytically, and the species-associated spectra (SAS) were determined numerically using a matrix approach, treating first the experiments with longer t1 delays and then using the already determined SAS for modeling the experiments with shorter t1 delays. Strong vibronic coupling of νCC and of vibrationally hot states makes the analysis complicated. Nevertheless, the SAS were identified and the ET rates of the vibrationally excited species, S2Atr, S2Btr and S2Bh, were determined. The results show that the ET rate for the S2A species is ca. 1.2-fold slower when the νCC mode is excited. The ET rate for species S2B is slower by ca. 1.3-fold if the compound is vibrationally hot and is essentially unchanged when the νCC mode is excited. The SAS determined for the tr and h species resemble the SAS for their respective precursor species in the 2-pulse transient absorption experiments, which validates the procedure used and the results.

A universal synthesis strategy of Pd-based trimetallic nanowires for efficient alcohol electrooxidation.

Trimetallic nanowires (NWs) have drawn much attention in efficient alcohol oxidation reaction (AOR) due to their unique features, including high atomic utilization efficiency and fast electron transfer ability. However, a universal strategy to synthesize Pd-based trimetallic NWs with high catalytic performance is still lacking. Herein, we develop a universal method for facile synthesis of PdBiM (M = Pt, Ru, Ir, Co, Cu) NWs with excellent AOR activities. By taking PdBiPt NWs as an example, the formation mechanism was investigated, and it is found that introduction of bismuth (Bi) plays an important role in facilitating the formation of the NW structure. Moreover, the PdBiPt NWs deliver an outstanding performance toward both the ethanol oxidation reaction (EOR) and the methanol oxidation reaction (MOR). Density functional theory (DFT) calculations together with experimental results disclose that the moderate electronic structure of trimetallic PdBiPt NWs can optimize the adsorption of OHads and weaken the adsorption of COads, thereby leading to the substantially enhanced AOR performance. We believe that this work can inspire the design of multimetallic NWs as high-performance catalysts.

Fe–CuP nanocubes for nitrate-to-ammonia conversion

Fe-CuP prepared through phosphorization, possesses distinct surface morphology, fast electron transfer, and an increase in active sites, which is detrimental to the reduction reaction.

Unveiling the capability of novel cobalt/barium stannate nanoparticles embedded functionalized MWCNTs nanocomposite for electrochemical investigation of antibiotic drug nifuroxazide

Nifuroxazide (NFR) is a class of synthetic broad-spectrum antibiotics and recently was proven to have anticancer properties, which are widely used to treat infectious diarrhea and targeted anticancer therapeutic. However, clinical studies have shown that long-term consumption of nitrofurans can lead to numerous side effects on human health. To address these issues, very important to fabricate a hybrid sensor for highly accurate and ultra-low sensing of NFR in biological fluids. Herein, we designed a novel cobalt/barium stannate@functionalized MWCNT (CBS@f-MWCNT) using a simple ultrasonication route. The synthesized CBS@f-MWCNTs nanocomposite were meticulously inspected for their physicochemical and structural characteristics for comprehensive understanding. The CBS@f-MWCNT demonstrates excellent electrolytic response for NFR reduction due to synergistic effects, enhanced electrochemical active site, and fast electron transfer. The significant electrocatalytic mechanism of NFR exhibited that an equal number of protons (4H+) and electrons (4e–) participated in the process. Under the optimized conditions, the experimental results exposed that wide linear range (0.05–343.6 μM), an excellent limit of detection (LOD) of 0.015 μM, and a sensitivity of 1.07 μA μM−1 cm−2. Further, the electrochemical sensor reveals excellent selectivity, repeatability (RSD = 0.73 %), reproducibility (RSD = 3.1 %), and stability (92 %). Moreover, the practicability of the proposed sensor was verified for the detection of NFR in biological samples with a satisfactory relative recovery (>99.5 %). Therefore, this study not only provides a straightforward method to construct nanocomposites but also boosts the electrochemical performance for the determination of antibacterial drugs.

Rational design of N-doped C-encapsulated flower-like nickel-based heterostructured microsphere anodes for high-capacity and stable lithium storage.

Designing a unique morphology and nanoarchitecture with a heterostructure is regarded as an efficient strategy to achieve lithium-ion batteries (LIBs) with high capacity and cycle life. Herein, N-doped C-encapsulated flower-like NiS/Ni3(BO3)2 heterostructures (NiS/Ni3(BO3)2/NC) with a core-shell morphology are successfully synthesized by a facile general method to improve the rate performance and prolong the cycle life of LIBs. The coated NC layer and core-shell structure with elasticity can relieve the volume expansion during the lithiation/delithiation process to strengthen the stability of the structure. Moreover, the NC layer and NiS/Ni3(BO3)2/NC heterostructure can enhance the electronic conductivity of the electrode and guarantee fast and unimpeded electron transfer channels, thereby improving the electrochemical reaction kinetics. Owing to the synergy of heterostructures and core-shell layer, the as-synthesized NiS/Ni3(BO3)2/NC anode acquires a specific charge capacity of 549 mA h g-1 at 0.2 A g-1 after 100 cycles; meanwhile, a reversible capacity of 322 mA h g-1 can be maintained even at 1 A g-1 after 500 cycles. This study develops a universal interface manipulation strategy for the synthesis of M3B2O6-based or/and other advanced transition metal compound anode materials for the practical applications of LIBs.

An in situ exsolved Cu-based electrocatalyst from an intermetallic Cu5Si compound for efficient CH4 electrosynthesis.

A Cu-based electrocatalyst (e-Cu5Si) is developed by in situ exsolving ultrathin SiOx layer-coated CuO/Cu nanoparticles (<100 nm) on the surface of a conductive intermetallic Cu5Si parent. This specially designed e-Cu5Si catalyst exhibits high performance for the CO2 reduction reaction (CO2RR), which affords an excellent CH4 faradaic efficiency (FE) of 49.0% with partial current density of over 140.1 mA cm-2 at -1.2 V versus reversible hydrogen electrode (RHE) in a flow cell, with outstanding stability. The strongly coupled multiphase interfaces among the SiOx layer, CuO/Cu species, and substrate contribute to fast interfacial electron transfer for the CO2RR. Moreover, in situ Raman analysis suggests that the ultrathin SiOx layer simultaneously stabilizes the active Cu1+ species and promotes the protonation of *CO to form *CHxO, thereby greatly improving overall selectivity and activity of CH4 production.

A Poly(L-Arginine)-Based Electrochemical Sensor for Simultaneous Determination of Uric Acid, Tryptophan, and Hypoxanthine

This study presents the development of an efficient and cost-effective voltammetric sensor for the individual and simultaneous determination of uric acid (UA), tryptophan (Try) and hypoxanthine (HX), the three important biomarkers in the human body. The sensor consists of glassy carbon electrode (GCE) modified with the conducting layer of poly(L-Arginine) (p-Arg) prepared by the electropolymerisation of L-Arginine using cyclic voltammetry. p-Arg modified GCE (p-Arg/GCE) provided well-resolved and improved electrooxidation responses for UA, Try, and HX due to the greater electrocatalytic activity and fast electron transfer ability of the polymer layer. The fabricated sensor was characterised using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Atomic Force Microscopy (AFM), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Electrochemical Impedance Spectroscopy (EIS) and electroactive surface area calculations. Under optimal analytical conditions, determination of the three analytes was possible over wide linear ranges with the limit of detection of 1.97 × 10−8 M, 4.43 × 10−8 M, and 8.44 × 10−9 M, respectively for UA, Try, and HX. Practical utility of the sensor was successfully verified in synthetic urine and blood serum samples and determination of Try and HX was carried out in dietary supplements and commercially available samples of tea and coffee, respectively.

Achieving super lithium storage of FeC2O4/Gs composites with dual-level structured graphene sheets through electrostatic adherence

FeC2O4/Gs composites with dual-level structured graphene sheets were constructed via electrostatic adherence technology, which provide a facile pathway for fast electron transfer, more channels for Li+ diffusion, and excellent structural stability.

Designing a Schottky coupled p–n junction to enhance the kinetic behavior of the oxygen evolution reaction

The design of the energy band structure modulates the surface charge distribution and optimizes energy levels of Fe3C-NG@NiFe, the construction of the double heterojunction introduces additional active sites and fast electron transfer for the OER.

Constructing self-standing Fe2O3-Pt/NF nanoflowers with synergistic active sites for efficient electrocatalytic overall (sea) water splitting.

Designing cost-effective and highly stable heterostructures with synergistic active sites could simultaneously catalyze the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) for (sea) water splitting. However, there are still challenges in maintaining the catalytic performance of individual materials and in constructing intimate interfaces. Herein, a novel corrosion engineering method is provided to prepare self-standing Fe2O3-Pt/NF nanoflowers where ultra-small amounts of Pt combined with Fe2O3 are in situ grown on nickel foam (NF) in the corrosion system of "H2PtCl6-NaCl-FeCl3". The synthesized Fe2O3-Pt/NF shows the presence of a Pt-O bond, which can regulate the electronic structure of the active sites and optimize the binding energy of the reaction intermediates, leading to an improvement in catalytic performance. Compared with Pt/NF and FeOOH/NF, the Fe2O3-Pt/NF heterostructure exhibits remarkable electrocatalytic activities with overpotentials reaching 94 mV and 265 mV for the HER and OER, respectively, at a high current density of 100 mA cm-2 in alkaline solution. Furthermore, the self-assembled electrolytic cell employing Fe2O3-Pt/NF as the bifunctional electrode only requires potentials of 1.60 V and 1.61 V to achieve a current density of 100 mA cm-2 in overall water and seawater splitting, respectively. This material remained stable for 10 hours without obvious attenuation, indicating its good environmental adaptability and stability. Specifically, the enhanced catalytic activity and stability can be ascribed to the abundant active sites of nanoflowers, fast electron transfer rate of intimate interfaces, and strong electronic interaction between Pt atoms and Fe2O3. This work provides a new insight into the construction of highly efficient co-catalysts with intimate interfaces based on corrosion engineering methods.

Ti3C2Tx MXene-supported ruthenium nanoclusters for efficient electrocatalytic hydrogen evolution.

Developing an efficient and stable catalyst is both attractive and challenging for the electrochemical hydrogen evolution reaction (HER) due to the aggravation under the operating environment. MXene (Ti3C2Tx) is a potential catalyst support because of its abundant surface functional groups and unique hydrophilicity. However, anchoring noble metals onto MXene to construct high-performance electrocatalysts still presents some challenges. Herein, we present an MXene nanoparticle-supported Ru nanocluster (Ru@MXene-NP) electrocatalyst for HER. The Ru@MXene-NP not only effectively prohibits self-stacking but also ensures the full exposure of Ru nanoclusters. Thus, the Ru@MXene-NP catalyst exhibits an overpotential of 38.4 mV at 10 mA cm-2 and a Tafel slope of 26.4 mV dec-1 in an acidic medium, showcasing superior performance compared to most previously reported MXene-based catalysts. The small Tafel slope and low charge transfer resistance (Rct = 0.39 Ω) value indicate its fast electron transfer behavior. In addition, cyclic voltammetry curves and chronoamperometry tests demonstrate the high stability of Ru@MXene-NP. This work offers a novel perspective for designing catalysts by supporting noble metal nanoclusters on the MXene substrate's surface.

Easily constructed porous silver films for efficient catalytic CO2 reduction and Zn-CO2 batteries.

For the electroreduction of carbon dioxide into high value-added chemicals, highly active and selective catalysts are crucial, and metallic silver is one of the most intriguing candidate materials available at a reasonable cost. Herein, through a novel two-step operation of Ag paste/SBA-15 coating and HF etching, porous silver films on a commercial carbon paper with a waterproofer (p-Ag/CP) could be easily fabricated on a large scale as highly efficient carbon dioxide reduction reaction (CO2RR) electrocatalysts with a CO Faraday efficiency (FECO) as high as 96.7% at -1.0 V vs. the reversible hydrogen electrode (RHE), and it still reaches up to 90% FECO over applied potentials ranging from -0.8 to -1.1 V vs. the RHE. Meanwhile, the membrane electrode assembly (MEA) utilizing the p-Ag/CP catalyst has achieved a current density, FECO, and stability of ∼60 mA cm-2, >91%, and 11 h, respectively. Furthermore, the assembled aqueous Zn-CO2 battery using p-Ag/CP cathode yielded a peak power density of 0.34 mW cm-2, 75 charge-discharge cycles for 25 h, and 64% FECO at 2.5 mA cm-2. Compared with flat Ag/CP, the significant enhancement in the CO2RR activity of p-Ag/CP was mainly attributed to the distinctive porous structure and an improved three-phase boundary, which is capable of inducing the stabilization of *COOH intermediates, increased active specific surface areas, fast electron transfer kinetic and mass transportation. Further, theoretical calculations revealed that p-Ag/CP possessed an optimized energy barrier for *COOH intermediates.

Simultaneous derivatization and exfoliation of a multilayered Ti3C2Tx MXene into amorphous TiO2 nanosheets for stable K-ion storage.

Two-dimensional transition metal compounds (2D TMCs) have been widely reported in the fields of energy storage and conversion, especially in metal-ion storage. However, most of them are crystalline and lack active sites, and this brings about sluggish ion storage kinetics. In addition, TMCs are generally nonconductors or semiconductors, impeding fast electron transfer at high rates. Herein, we propose a facile one-step route to synthesize amorphous 2D TiO2 with a carbon coating (a-2D-TiO2@C) by simultaneous derivatization and exfoliation of a multilayered Ti3C2Tx MXene. The amorphous structure endows 2D TiO2 with abundant active sites for fast ion adsorption and diffusion, while the carbon coating can facilitate electron transport in an electrode. Owing to these intriguing structural and compositional synergies, a-2D-TiO2@C delivers good cycling stability with a long-term capacity retention of 86% after 2000 cycles at 1.0 A g-1 in K-ion storage. When paired with Prussian blue (KPB) cathodes, it exhibits a high full-cell capacity of 50.8 mA h g-1 at 100 mA g-1 after 140 cycles, which demonstrates its great potential in practical applications. This contribution exploits a new approach for the facile synthesis of a-2D-TMCs and their broad applications in energy storage and conversion.