Multifunctional Electrocatalysts Research Articles

Boosting Oxygen Reduction Reaction with Fe-Based Single-Atom Catalysts: The Role of Cluster Interactions

Fuel cells (FCs) have emerged as a promising alternative for efficient electricity production in the future [1]. However, their widespread commercialization is hindered by their prohibitive cost due to the large amount of platinum used in these electrochemical systems [2]. Platinum is used to accelerate the unfavorable kinetics of the cathodic oxygen reduction reaction (ORR) [3]. To achieve large-scale and cost-effective development of FCs, it is essential to find high-performance platinum-free catalysts. Two solutions are mainly reported in the literature: the development of non-precious metal-based carbon catalysts and metal-free carbon catalysts. However, the work reported on these two types of carbon catalysts is sometimes contradictory regarding the actual nature of the active sites and the mechanisms of reduction of oxygen molecules on the catalyst [4].Pyrolyzed metal-nitrogen-carbon (M-N-C) catalysts for the ORR, especially single-atom catalysts (SACs), have been widely studied because they exhibit excellent electrocatalytic performance, thanks to the high content of metal atoms anchored on a carbon support [5]. Recent research has indicated that the combination of single-atom active sites with metal nanoclusters can further improve the catalytic activity, but the underlying mechanism remains unclear [6]. Therefore, it is necessary to develop model catalysts based on both single-atoms and nanoclusters to better understand their catalytic activity.In this work, we prepared nitrogen-doped and iron-doped carbon catalysts (called Fe-NC below) with precise control of the type of iron in the material. First, the functionalization of an activated carbon was performed by carbonizing it under air in the presence of urea. Then, the sample was placed in an autoclave for hydrothermal treatment in the presence of FeCl3.6H2O to allow the incorporation of iron, and thermal post-treatment was applied to synthesize model catalysts (Fig. 1a). The precursor ratio and final pyrolysis temperature were adjusted and optimized to produce either iron-based single atoms (SA) (here referred to as FeSA-NC) or atomic clusters (AC) associated with single atoms (here referred to as FeSA+AC-NC). The results show that the iron-based catalysts exhibit outstanding catalytic activity (Fig. 1b) and durability (Fig. 1c) in alkaline medium for the ORR, even better than commercial Pt (20 wt.%)/C in the case of FeSA+AC-NC. The analysis provided insight into the development of highly efficient multifunctional electrocatalysts, where the presence of iron nanoclusters was found to be a crucial determinant of the catalytic activity for the ORR.[1] M.K. Debe, Electrocatalyst approaches and challenges for automotive fuel cells, Nature. 486 (2012) 43–51. https://doi.org/10.1038/nature11115.[2] C. Sealy, The problem with platinum, Mater. Today. 11 (2008) 65–68. https://doi.org/10.1016/S1369-7021(08)70254-2.[3] M. Borghei, J. Lehtonen, L. Liu, O.J. Rojas, Advanced Biomass-Derived Electrocatalysts for the Oxygen Reduction Reaction, Adv. Mater. 30 (2018) 1703691. https://doi.org/10.1002/adma.201703691.[4] A. Dessalle, J. Quílez-Bermejo, V. Fierro, F. Xu, A. Celzard, Recent progress in the development of efficient biomass-based ORR electrocatalysts, Carbon. 203 (2023) 237–260. https://doi.org/10.1016/j.carbon.2022.11.073.[5] K. Liu, J. Fu, Y. Lin, T. Luo, G. Ni, H. Li, et al., Insights into the activity of single-atom Fe-N-C catalysts for oxygen reduction reaction, Nat. Commun. 13 (2022) 2075. https://doi.org/10.1038/s41467-022-29797-1.[6] X. Wan, Q. Liu, J. Liu, S. Liu, X. Liu, L. Zheng, et al., Iron atom–cluster interactions increase activity and improve durability in Fe–N–C fuel cells, Nat. Commun. 13 (2022) 2963. https://doi.org/10.1038/s41467-022-30702-z. Figure 1

Construction of Dual-atom catalysts on MoTe2 monolayer to achieve high-efficiency OER/ORR performance

Developing efficient, economical and environmentally friendly multifunctional electrocatalysts is a prerequisite for developing renewable energy conversion and storage technologies. Dual-atom catalysts have significant catalytic performance compared to monoatomic catalysts due to the larger metal loading and synergistic effects between metal atoms, and the reduction of overpotentials and increase of the reaction rate are the keys to obtaining high-performance OER/ORR bifunctional electrocatalysts, as determined by the electrocatalytic thermodynamics and kinetics of electrocatalysis. This work investigates efficient electrocatalysts with bifunctional catalytic activity for OER/ORR. Modifying the MoTe2 material by doping with transition metal atoms shows that the catalysts exhibit better electrochemical stability due to higher solvation potentials. The Pd2@MoTe2 catalysts were screened for bifunctional electrocatalysts due to the change in the local chemical environments. The Pd2@MoTe2 catalysts have excellent bifunctional electrocatalytic activity with overpotentials for OER and ORR of 0.23 and 0.21 V. The results show it can compete with and outperform the currently developed catalysts. This excellent catalytic activity can be attributed to the change in the coordination environment around the modified material, resulting in a change in electronic properties. This effectively ensures excellent electrical conductivity and electron transfer to modulate the strength of adsorbate interactions and optimize the catalytic performance. This work provides new ideas for understanding and optimizing the active center of bifunctional catalysts and new strategies for designing high-performance multifunctional electrocatalysts for metal-air batteries.

Modulating the exposed facets of Pd-Pb intermetallic compounds via morphology engineering for efficient multifunctional electrocatalysts

To develop Pd-based intermetallic compounds (IMCs) nanomaterials with specific morphologies for exposing specific facets is essential yet full of challenges for highly efficient electrocatalysts. Herein, we utilized morphology engineering to successfully acquire Pd-Pb concave nanocubes (Pd-Pb CNCs) with Pd3Pb IMC phase and exposing (200) facet mainly. The Pd-Pb CNCs catalyst displays the ultrahigh activity of 4.01 A mgPd-1 for ethanol oxidation reaction (EOR), surpassing than that of Pd-Pb nanoparticles with Pd3Pb IMC phase but exposing (111) facet mainly, and far exceeding than commercial Pd/C. Density functional theory simulation manifests that the excellent EOR activity for Pd-Pb CNCs is attributed to the weakened reaction intermediates adsorption on catalyst surface. Importantly, the Pd-Pb CNCs are also with excellent reactivities for methanol oxidation reaction and glycerol oxidation reaction, indicating potentials as outstanding multifunctional electrocatalysts. This work may not only furnish a simple strategy for fabricating Pd-based IMCs exposing specific facets, but also promote their high-efficient applications in alcohol oxidation reactions and beyond.

A Route to Complex Materials Consisting of Multiple Crystalline Phases Ir‐Ru‐IrxRu1‐xO2 as Multifunctional Electrocatalysts

AbstractThe synthesis of catalytic materials containing active sites of various oxidation states (metal, oxide, etc.) for the dual use in reduction and oxidation reactions remains challenging because most of the reported methods for the metallic state are often incompatible with those for the oxide state. A new methodology is reported for the synthesis of a library of bimetallic metal‐oxide materials containing three crystalline phases Ir‐Ru‐IrxRu1‐xO2 by combining the calcination under air and the polymerization of aniline in the presence of IrCl3 and RuCl3 precursors. Morphology, structure, and surface oxidation state studies (XRD, SEM/EDX, S/TEM, XPS) confirm the hypothesis that IrCl3 evolves to Ir while RuCl3 evolves to RuO2 during the calcination under air. An Ir:Ru atomic ratio of 50:50 can be converted into a heterogeneous nanostructure composed of Ir, Ru, and IrxRu1‐xO2 to date, with remarkable catalytic activity for both hydrogen evolution reaction (HER) with a small overpotential of 40 mV and oxygen evolution reaction (OER) with a small overpotential of 290 mV at the metric current density of 10 mA cm−2 in 0.5 m H2SO4. The results can serve as a platform for the development of efficient multifunctional materials for practical use in both catalytic oxidation and reduction reactions.

Novel structured carbon nanotubes fiber based microelectrodes for efficient electrochemical water splitting and glucose sensing

An efficient electrocatalyst composed of nickel and cobalt selenide over unique structure carbon nanotubes (NiCo-Se@CNTs) fiber has been fabricated via a single-step hydrothermal method which showed efficient electrocatalytic performance towards electrochemical non-enzymatic glucose sensing and overall water splitting applications. The structural and elemental composition of a modified electrode (NiCo-Se@CNTs) was ascertained via transmission electron microscopy (TEM), X-rays diffraction (XRD) pattern, X-rays photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) along with energy dispersive X-ray spectroscopy (EDX) techniques. Modified fiber-based electrode was used for the electrochemical water splitting which showed a low overpotential value (η10 = 260 mV) with a corresponding Tafel slope of 138 mV dec−1. These values are far superior in contrast with pristine CNTs fiber, having 384 mV overpotential and 318 mV dec−1 of Tafel slope. In extension, while studying overall water splitting by engaging both modified CNTs fiber as anode and cathode, it exhibited excellent performance with an overpotential (η10) of 297 mV and corresponding Tafel slop of 159 mV dec−1. The fabricated electrode was further investigated for electrochemical glucose sensing which exhibited excellent performance towards the glucose detection with a linear dynamic range of up to 10 mM, a detection limit of 0.59 μM in an alkaline condition (pH=13) and high sensitivity of 813 mAmM−1cm−2. The outcomes demonstrated that fabricated fiber (NiCo-Se@CNTs) might be a promising material in future as a multifunctional electrocatalyst for flexible and wearable energy and sensing related applications.

Self-assemble strategy to fabricate multifunctional electrocatalyst for efficient and energy-saving water splitting

It is a significant and challenging task to develop cheap, high-performance, and stable electrocatalysts for electrochemical water splitting. However, owing to the ponderous kinetics and high thermodynamic potential essential conditions of the anodic oxygen evolution reaction (OER), more energy is needed for the water splitting. Introducing more easily oxidized small molecules at the anode can achieve more energy-efficient electrochemical water hydrogen conversion. Herein, a high-capacity electrocatalyst (namely Co4S3/WC/Nb4C3Tx@NC) for water splitting was prepared by a simple way of mixing conductive particles of delaminated niobium carbide (Nb4C3Tx) MXene into transition metal sulfide/carbides. Meanwhile, the synergistic effect of Co4S3 and WC nanoparticles can enhance the activity of a single component and optimize the adsorption of hydrazine. The carbon layer can provide protection for the catalyst, and the addition of Nb4C3Tx MXene can improve the conductivity of the catalyst and provide more adsorption active sites. As a result, Co4S3/WC/Nb4C3Tx@NC catalyst presents a noteworthy activity and long-life durability with a lower overpotential of 84 or -66 mV to obtain 10 mA cm−2 for HER or hydrazine oxidation reaction (HzOR) in 1.0 M KOH, respectively. As expected, the dual electrode hydrazine-assisted electrolyzer by using the Co4S3/WC/Nb4C3Tx@NC as a multifunctional catalyst, generation of hydrogen can be easily realized at a much lower voltage (0.211 V@10 mA cm−2), which is much convenient than that of classical water splitting. Our work proposes an efficient and energy-saving MXene-based electrocatalyst for electrochemical water splitting.

A facile and green strategy for mass production of dispersive FeCo-rich phosphides@N,P-doped carbon electrocatalysts toward efficient and stable rechargeable Zn-air battery and water splitting

One key step for advancing the widespread practical application of rechargeable metal-air batteries and water electrolysis fundamentally relies on the development of cost-effective multifunctional electrocatalysts toward oxygen and hydrogen-involving reactions. The present work initiates a tofu-derived one-pot strategy for green, facile, and mass production of highly active and stable catalyst toward oxygen reduction/evolution and hydrogen evolution reactions, through the preparation of Fe/Co cross-linked tofu gel and the subsequent pyrolysis. Despite the free use of additional N/P precursors or pore-forming agents, the as-prepared materials comprise highly dispersive FeCo-rich phosphides nanoparticles and porous N,P co-doped carbon network inherited from the tofu skeleton. The resultant catalysts exhibit remarkably enhanced trifunctional activities as compared to the Fe2P and Co2P counterparts, along with better long-term stabilities than the benchmark RuO2 and Pt/C catalysts. Accordingly, the as-assembled Zn-air battery delivers a large power density (174 mW cm−2) with excellent cycle stability (the gap of charge/discharge voltage@10 mA cm−2 increases by 0.01 V after 720 h of operation, vs. 0.16 V of Pt/C-RuO2 based battery after 378 h). Furthermore, the as-constructed alkaline electrolyzer just requires a small voltage of 1.55 V@10 mA cm−2, which outperforms nearly all of those of biomass-derived electrocatalysts ever reported, and that of noble metal catalysts-based electrolyzers (1.72 V@10 mA cm−2 for Pt/C-RuO2), underscoring their bright future toward commercial applications in green energy conversion devices.

Computational Design of Ni6@Pt1M31 Clusters for Multifunctional Electrocatalysts.

High-efficiency and low-cost multifunctional electrocatalysts for hydrogen evolution reaction (HERs), oxygen evolution reaction (OERs) and oxygen reduction reaction (ORRs) are important for the practical applications of regenerative fuel cells. The activity trends of core-shell Ni6@M32 and Ni6@Pt1M31 (M = Pt, Pd, Cu, Ag, Au) were investigated using the density functional theory (DFT). Rate constant calculations indicated that Ni6@Pt1Ag31 was an efficient HER catalyst. The Volmer-Tafel process was the kinetically favorable reaction pathway for Ni6@Pt1M31. The Volmer-Heyrovsky reaction mechanism was preferred for Ni6@M32. The Pt active site reduced the energy barrier and changed the reaction mechanism. The ORR and OER overpotentials of Ni6@Pt1Ag31 were calculated to be 0.12 and 0.33 V, indicating that Ni6@Pt1Ag31 could be a promising multifunctional electrocatalyst. Ni6@Pt1M31 core-shell clusters present abundant active sites with a moderate adsorption strength for *H, *O, *OH and *OOH. The present study shows that embedding a single Pt atom onto a Ni@M core-shell cluster is a rational strategy for designing an effective multifunctional electrocatalyst.

Tetraiodo Fe/Ni phthalocyanine-based molecular catalysts for highly efficient oxygen reduction reaction and oxygen evolution reaction: Constructing a built-in electric field with iodine groups

In this paper, we report on the preparation and catalysis of a bifunctional molecular catalyst (Fe[Pc(I)4]+Ni[Pc(I)4]@NCPDI) for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable Zn-air batteries. This catalyst is prepared by self-assembling tetraiodo metal phthalocyanines (Fe[Pc(I)4] and Ni[Pc(I)4]) on a 2D N-doped carbon material (NCPDI) through π-π interactions. The introduction of iodine groups in the edge of phthalocyanines controls the density of electron cloud and electrostatic potential around Fe-N/Ni-N sites and constructs a built-in electric field that facilitates directional transport of charges, enhancing the catalytic activity of the catalyst. Density functional theory (DFT) calculations support this mechanism by showing a reduced energy barrier for the ORR rate-determining step (RDS). The Fe[Pc(I)4]+Ni[Pc(I)4]@NCPDI exhibits excellent performance outperforming 20 wt% Pt/C and single-molecule self-assembled Fe[Pc(I)4]@NCPDI and Ni[Pc(I)4]@NCPDI, with a half-wave potential of E1/2 = 0.940 V in the ORR process under alkaline condition. During the OER process, Fe[Pc(I)4]+Ni[Pc(I)4]@NCPDI exhibited a low overpotential of 298 mV at 10 mA cm−2 under the alkaline condition, which is much better than RuO2, Fe[Pc(I)4]@NCPDI and Ni[Pc(I)4]@NCPDI. The catalyst also demonstrates excellent catalysis and durability in rechargeable Zn-air batteries. This work provides a simple and specific method to develop efficient multifunctional molecular electrocatalysts.

G-C3N4/Bromocobaloxime nanocomposites as multi-functional electrocatalysts for water splitting and energy storage

The depletion of fossil fuels necessitates the search for alternative sources of energy and energy storage for long-term usage. Recently graphitic carbon nitride (g-C3N4) based materials have gained attention due to their enhanced activity compared to previously tested materials. But the poor electron mobility of g-C3N4 continues to cause a significant energy loss in the electrocatalytic processes. Herein we report the synthesis and characterization of g-C3N4/Bromocobaloxime composites and their electrocatalytic applications towards hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and energy storage. Bromocobaloximes [BrCo(dpgH)2B] (B1-B4) containing diphenylglyoxime [dpgH] as the equatorial ligand and functionalized neutral bases such as Isonicotinic acid (1), Pyridine-3,5-dicarboxylic acid (2), Indole-2-carboxylic acid (3) and p-Aminobenzoic acid (4) were synthesized using the standard procedure. The g-C3N4/Cobaloxime nanocomposites (g-C3N4/B1, g-C3N4/B2, g-C3N4/B3 and g-C3N4/B4) were prepared using g-C3N4 nanosheets by solvothermal method. The prepared nanocomposites were characterized by FT-IR, UV-DRS, XRD, SEM, EDAX, TEM and XPS analysis. The electrochemical HER studies of the synthesized nanocomposites showed low overpotentials in the range of 51 to 228 mV at −10 mAcm−2 and the OER studies exhibited overpotentials in the range of 310 to 460 mV at 10 mAcm−2. Among them nanocomposite g-C3N4/B2 showed a lower Tafel slope of 45 mV/dec for HER and 112 mV/dec for OER. The supercapacitance studies indicated that among the nanocomposites, g-C3N4/B1 showed a good specific capacitance of 302 F/g at 0.5 A/g. The increased electrochemical performance of the synthesized nanocomposites is due to the incorporation of cobaloximes containing carboxylic acid functionalized neutral bases into the g-C3N4 nanosheets, which increases the electron mobility. This will lead to explore the applications of g-C3N4/metal complexes towards energy conversion by tuning the ligands in the metal complexes.

Building up a view and understanding of the multifunctional activity of black phosphorous nanosheet modified with the metal atom.

Constructing metal-semiconductor interfaces by loading metal atoms onto two-dimensional material to build atomically dispersed single-atom catalysts (SACs) has emerged as a new frontier for improving atom utilization and designing multifunctional electrocatalysts. Nowadays, studies on black phosphorus nanosheets in electrocatalysis have received much attention and the successful preparation of metal nanoparticle/black phosphorus (BP) hybrid electrocatalysts indicates BP nanosheets can serve as a potential support platform for SACs. Herein, by using large-scale abinitio calculations, we explored a large composition space of SACs with transition metal atoms supported on BP monolayer (M-BP) and built a comprehensive picture of activity trend, stability, and electronic origin towards oxygen reduction and evolution reaction (ORR and OER) and hydrogen evolution reaction (HER). The results show that the catalytic activity can be widely tuned by reasonable regulation of metal atoms. Ni-, Pd-, and Pt-BP could effectively balance the binding strength of the target intermediates, thus achieving efficient bifunctional activity for OER and ORR. Favorable bifunctional catalytic performance for OER and HER can be realized on Rh-BP. Especially, Pt-BP exhibits promising trifunctional activity towards OER, ORR, and HER. Multiple-level corrections among overpotential, Gibbs free energy, orbital population, and d-band center reveal that the trend and origin of catalytic activity are intrinsically determined by the d-band center of metal sites. The thermodynamic and dynamic stability simulations demonstrate that the active metal centers are firmly anchored on BP substrate with intact M-P bonds. These findings provide a theoretical basis for the rational design of BP-based SACs toward promising multifunctional activity.

Multifunctional molybdenum-tuning porous nickel-cobalt bimetallic phosphide nanoarrays for efficient water splitting and energy-saving hydrogen production

The sluggish kinetics of the hydrogen evolution reaction (HER) and substantial barriers in the oxygen evolution reaction (OER) significantly impede its application in hydrogen production. To address this issue and enhance energy efficiency in hydrogen generation, we explored a high-activity alkaline HER catalyst while concurrently coupling it with the urea oxidation reaction (UOR). In this work, we designed and synthesized porous molybdenum (Mo)-modulated nickel-cobalt bimetallic phosphide nanoarrays (M0.3NCP@NF). This multifunctional self-supported electrocatalyst demonstrates superior performance in HER, OER, and UOR. The introduction of Mo, in the form of CoMoO4 nanoparticles, promotes interfacial electron transfer to reduce the electron density around the cations in phosphides, enhancing the kinetics and intrinsic activity. Furthermore, the morphological changes induced by Mo accelerate both electron and mass transfer processes. Density functional theory and operando electrochemical impedance spectroscopy indicate that Mo introduction optimizes the interaction with HER intermediate H*, facilitating the conversion to a high-valent active intermediate for OER and accelerating UOR kinetics. Benefiting from dual optimization of morphology and structure, the as-prepared M0.3NCP@NF electrocatalyst demonstrates outstanding HER, OER, and UOR performances. Notably, a full urea electrolysis device powered by M0.3NCP@NF operates with a cell voltage of only 1.53 V to achieve a current density of 100 mA cm−2. which is 240 mV lower than that of conventional water electrolysis, demonstrating the competitive potential of our approach for efficient and energy-saving hydrogen production, along with simultaneous urea wastewater remediation.

Dual Single-Atomic Co-Mn Sites in Metal-Organic-Framework-Derived N-Doped Nanoporous Carbon for Electrochemical Oxygen Reduction.

Synthesizing dual single-atom catalysts (DSACs) with atomically isolated metal pairs is a challenging task but can be an effective way to enhance the performance for electrochemical oxygen reduction reaction (ORR). Herein, well-defined DSACs of Co-Mn, stabilized in N-doped porous carbon polyhedra (named CoMn/NC), are synthesized using high-temperature pyrolysis of a Co/Mn-doped zeolitic imidazolate framework. The atomically isolated Co-Mn site in CoMn/NC is recognized by combining microscopic as well as spectroscopic techniques. CoMn/NC exhibited excellent ORR activities in alkaline (E1/2 = 0.89 V) as well as in acidic (E1/2 = 0.82 V) electrolytes with long-term durability and enhanced methanol tolerance. Density functional theory (DFT) suggests that the Co-Mn site is efficiently activating the O-O bond via bridging adsorption, decisive for the 4e- oxygen reduction process. Though the Co-Mn sites favor O2 activation via the dissociative ORR mechanism, stronger adsorption of the intermediates in the dissociative path degrades the overall ORR activity. Our DFT studies conclude that the ORR on an Co-Mn site mainly occurs via bridging side-on O2 adsorption following thermodynamically and kinetically favorable associative mechanistic pathways with a lower overpotential and activation barrier. CoMn/NC performed excellently as a cathode in a proton exchange membrane (PEM) fuel cell and rechargeable Zn-air battery with high peak power densities of 970 and 176 mW cm-2, respectively. This work provides the guidelines for the rational design and synthesis of nonprecious DSACs for enhancing the ORR activity as well as the robustness of DSACs and suggests a design of multifunctional robust electrocatalysts for energy storage and conversion devices.

Structure‐property Relationship of Double Perovskite Oxide towards Trifunctional Electrocatalytic Activity: Strategy for Designing and Development

AbstractIn the present scenario, the paramount significant roles of various heterogeneous catalysts stimulate the modern technologies to underpin the benchmark requirements for the generation of sustainable energy by reducing toxic fossil fuel emissions. Such critical role necessitates further development of cost‐effective highly efficient and earth‐abundant multifunctional or trifunctional electrocatalysts to promote the advancement of electrochemical overall water splitting performances, yet it is extremely desirable. In this review context, we present the development of double perovskite (DP) oxides as robust trifunctional catalysts for electrochemical oxygen evolution reaction (OER), oxygen reduction reaction (ORR) and hydrogen evolution reactions (HER) by rational design of multiple cationic redox sites with stoichiometric oxygen amount. Particularly, we highlight the importance of the structural modifications via doping, surface structure and oxygen stoichiometry as key parameters to tune the electrocatalytic activities and understand the insight into activity and mechanism of this oxide family. This perspective also describes controlled synthesis protocols including the surface structure of double perovskite oxides are key techniques for realizing a correlation between structure‐activity relationships of these materials. Finally, it is concluded by outlining the several aspects of optimization strategies and computational opportunities can expand the future scope of double perovskite oxides as robust trifunctional electrocatalysts.

Hydrogen‐Bonded Organic Framework to Upgrade Cycling Stability and Rate Capability of Li‐CO2 Batteries

AbstractElaborately designed multifunctional electrocatalysts capable of promoting Li+ and CO2 transport are essential for upgrading the cycling stability and rate capability of Li‐CO2 batteries. Hydrogen‐bonded organic frameworks (HOFs) with open channels and easily functionalized surfaces hold great potential for applications in efficient cathodes of Li‐CO2 batteries. Herein, a robust HOFS (HOF‐FJU‐1) is introduced for the first time as a co‐catalyst in the cathode material of Li‐CO2 batteries. HOF‐FJU‐1 with cyano groups located periodically in the pore can induce homogeneous deposition of discharge products and accommodate volumetric expansion of discharge products during cycling. Besides, HOF‐FJU‐1 enables effective interaction between Ru0 nanoparticles and cyano groups, thus forming efficient and uniform catalytic sites for CRR/CER. Moreover, HOF‐FJU‐1 with regularly arranged open channels are beneficial for CO2 and Li+ transport, enabling rapid redox kinetic conversion of CO2. Therefore, the HOF‐based Li‐CO2 batteries are capable of stable operation at 400 mA g−1 for 1800 h and maintain a low overpotential of 1.96 V even at high current densities up to 5 A g−1. This work provides valuable guidance for developing multifunctional HOF‐based catalysts to upgrade the longevity and rate capability of Li‐CO2 batteries.

Fe doped Mo-Ni supramolecular coordination polymer based bifunctional oxygen electrocatalyst with high efficiency and duration for rechargeable zinc-air battery

In the present area of electrochemistry, due to the scarcity and unavailability of precious metals, it is a great challenge and a new opportunity to develop bifunctional electrocatalysts for zinc-air batteries (ZABs) with high activity, low cost and strong durability. In this study, an excellent electrocatalyst (Fe@MoNi/NCP-800) for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) was successfully prepared by pyrolyzing Fe2+ ion doped bimetallic Mo-Ni supramolecular coordination polymer (SCP) at 800 °C with carbon paper (CP) as self-supporting material. Owing to its unique FeNi alloy nanotube structure supported by the in situ formed MoN and the trimetallic synergies, the as-obtained electrocatalyst showed superior catalytic performance to that of commercial Pt/C half-wave potential (E1/2) of 0.846 V and RuO2 overpotential (η) of 300 mV. In addition, the ZABs prepared with Fe@MoNi/NCP-800 has a small charge–discharge voltage gap of 0.85 V, high energy efficiency of 35.25% and excellent cycle performance (308 h) at 10 mA cm−2. This research provides a very promising transition-metal alloy multifunctional electrocatalyst for the development of ZABs with high efficiency and duration, and a meaningful idea for the future rational design and synthesis of new coordination polymer or supramolecular coordination polymer-based electrocatalysts.

Hierarchical NiCo-LDH@MoS2/CuS composite as efficient trifunctional electrocatalyst for overall water splitting and asymmetric supercapacitor

The development of highly active and long-lived multifunctional electrocatalysts is a key priority to boost clean renewable energy technologies. It is difficult to construct such hierarchically structured materials with an efficient synergistic heterostructure technique to improve electrochemical performance. Here, a novel hierarchical NiCo-LDH@MoS2/CuS heterostructure (HS) was prepared by facile two-step hydrothermal synthesis for water splitting and supercapacitor applications. The hierarchical network of NiCo-LDH is grown on MoS2/CuS and is put forward based on various physio-chemical analysis. The hierarchical structure and heterostructure synergistic effect result in excellent HER (114 mV@10 mA cm−2) and OER (310 mV@10 mA cm−2) activity. Two electrode water-splitting cells (NiCo-LDH@MoS2/CuS||NiCo-LDH@MoS2/CuS) achieved a cell potential of 1.57 V@10 mA cm−2. NiCo-LDH@MoS2/CuS also exhibits the electrochemical charge storage property of 147.16 mAh g−1@0.2 A g−1. NiCo@MoS2/CuS||AC flexible solid-state asymmetric supercapacitor (FSSC) demonstrated charge storage of 226.08 mAh g−1 and energy density of 152.60 W h kg−1@0.2 A g−1 with 90.05 % retention rate, demonstrated the excellent cyclic and structural stability. The acquired knowledge from this study could be a novel strategy for designing hierarchical LDH-based heterostructures as electrode materials for water splitting and energy storage devices.

Establishing theoretical landscapes for identifying basal plane active sites in MBene toward multifunctional HER, OER, and ORR catalysts

Exploring multifunctional electrocatalysts to realize efficient hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) is urgently desired for developing novel renewable energy storage and conversion technologies. However, integrating these three merits in one single catalyst remains a big challenge due to the difficulty in balancing the adsorption strengths of multiple reaction intermediates. Herein, through first-principles calculations, we systematically investigated the electrocatalytic activity of M2B2, M3B4, and M4B6 type MBenes (M = Cr, Mn, Fe, Co, and Ni) for multifunctional HER, OER, and ORR. The results indicate that most of the investigated MBenes show outstanding catalytic activity for HER with hydrogen adsorption Gibbs free energy close to the optimal value (0 eV). Thereinto, Ni2B2 and Co3B4 MBenes can be promising multifunctional HER/OER/ORR electrocatalysts, and Fe3B4 MBene is expected to be a promising bifunctional electrocatalyst for HER/ORR. Especially, Ni2B2 MBene is even better than the benchmark RuO2 catalyst with ultralow low overpotentials of 0.26 and 0.30 V for OER and ORR, respectively. Then, we proposed that the overpotentials of OER/ORR can be well described by the varied ΔGOH* on MBene, which has been further illuminated through the d-band center and charge transfer analysis. Importantly, new scaling relations between the adsorption energies of OOH* and O* on MBenes have been established, where ΔGOOH* and ΔGO* possess different slopes versus ΔGOH*, allowing the significantly lower overpotentials of OER and ORR to be achieved. This work provides not only promising multifunctional HER/OER/ORR electrocatalysts but also new scaling relations to achieve the rational design of MBene-based electrocatalysts.

Abundant Exterior/Interior Active Sites Enable Three-Dimensional PdPtBiTe Dumbbells C-C Cleavage Electrocatalysts for Actual Alcohol Fuel Cells.

Developing high-activity electrocatalysts is of great significance for the commercialization of direct alcohol fuel cells (DAFCs), but it still faces challenges. Herein, three-dimensional (3D) porous PdPtBiTe dumbbells (DBs) were successfully fabricated via the visible photoassisted method. The alloying effect, defect-rich surface/interface and nanoscale cavity, and open pores make the 3D PdPtBiTe DBs a comprehensive and remarkable electrocatalyst for the C1-C3 alcohol (ethanol, ethylene glycol, glycerol, and methanol) oxidation reaction (EOR, EGOR, GOR, and MOR, respectively) in an alkaline electrolyte, and the results of in situ Fourier transform infrared spectra revealed a superior C-C bond cleavage ability. The 3D PdPtBiTe DBs exhibit ultrahigh EOR, EGOR, GOR, and MOR mass activities of 25.4, 23.2, 16.8, and 18.3 A mgPd + Pt-1, respectively, considerably surpassing those of the commercial Pt/C and Pd/C. Moreover, the mass peak power densities of 3D PdPtBiTe DBs in actual ethanol, ethylene glycol, glycerol, or methanol fuel cells increase to 409.5, 501.5, 558.0, or 601.3 mW mgPd + Pt-1 in O2, respectively. This study provides a new class of multimetallic nanomaterials as state-of-the-art multifunctional anode electrocatalysts for actual DAFCs.

Electronic modulation induced by decorating single-atomic Fe-Co pairs with Fe-Co alloy clusters toward enhanced ORR/OER activity

Modulating the electronic properties of single-atomic metal sites with metal clusters is a promising strategy for boosting their intrinsic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity. Herein, we report an effective isolation-confinement strategy for synthesis of well-dispersed Fe-Co atom clusters and N4Fe-CoN4 atomic pair sites on carbon nanofibers (marked as β-FeCo-PCNF), in which the addition of β-cyclodextrin is crucial in avoiding the agglomeration of metal species. The Fe-Co atomic clusters induce a downward shift in the d-band center of Fe-Co atomic sites, and this shift effectively reduces the adsorption energy of OOH* on Fe-Co atomic sites, resulting in lower energy barriers for ORR and OER. Remarkably, the β-FeCo-PCNF-based Zn-air battery exhibits excellent power density and cycling stability. This work paves the way for a universal strategy to regulate the electronic localization of atomic pair sites by alloy clusters and provides essential guidance for designing multifunctional electrocatalysts.