Multifunctional Electrocatalysts Research Articles

Environmentally Benign Synthesis of Copper Benzenetricarboxylic Acid MOF as an Electrocatalyst for Overall Water Splitting and CO2 Reduction

As a class of porous coordination polymers, metal organic frameworks (MOFs) have potential applications in many fields. In this work, a novel synthetic method, without using toxic solvents, has been developed to prepare HKUST-1 MOF nanoparticles from coprecipitation reaction of copper (II) chloride and 1,3,5-benzenetricarboxylic acid (trimesic acid) in distilled water. The synthesized nanoparticles were first characterized by X–ray diffraction (XRD), Fourier–transform infrared spectroscopy (FT–IR), and scanning electron microscopy (SEM). The flat–band potential, conduction band, and valence band edges of HKUST-1 nanoparticles were experimentally determined in alkaline solution, and UV–Vis diffuse reflectance spectra (DRS) analysis showed the band gap energy to be 2.5 eV. Electrochemical working electrodes were prepared by electrophoretic deposition of HKUST-1 on the surface of a stainless steel electrode for electrochemical voltammetry and impedance measurements. For the first time the prepared HKUST-1 nanoparticles were investigated as multifunctional electrocatalysts for both overall water splitting and CO2 reduction in alkaline solution. The Tafel plot was used to show the relationship between the over–potential (η) and the logarithmic current density, revealing the kinetic parameters of the electrochemical reactions. Furthermore, the Tafel slope was determined to be 190 mVdec−1, indicating that the Volmer mechanism with electrochemical desorption of hydrogen acts as the rate–determining step (RDS).

Nitrogen-doped 3D porous graphene coupled with densely distributed CoOx nanoparticles for efficient multifunctional electrocatalysis and Zn-Air battery

Highly efficient and low-cost multifunctional electrocatalysts play a crucial role in energy storage and conversion systems. Herein, a new strategy is developed based on a structured precursor to design and fabricate a hierarchical porous nitrogen doped graphene coupled with densely distributed CoO/Co3O4 heterostructure that exhibits outstanding multifunctional activities. With rational hybridization of graphene and bimetallic nanoparticles, the as-obtained NGPC@CoOx integrated densely distributed CoO/Co3O4 active nanoparticles to 3D interconnected hierarchical N-doped graphene mesh, which gives rise to a multifaceted capability for electron/ion transfer and redox catalyzing. The NGPC@CoOx possesses excellent durability with a superior E1/2 of 0.86 V for oxygen reduction reaction (ORR), and a relatively low potential for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) of 1.61 V, and -0.162 V at 10 mA cm−2, respectively. Additionally, the superior cycling durability and high power density of NGPC@CoOx-based zinc-air batteries (184.4 mW cm−2) further confirm the potential application of prototype devices. This work introduces a new perspective on developing efficient multifunctional electrocatalysts with a well-designed 3D structure anchored with densely distributed nanoparticles towards energy storage and conversion technologies.

Dianion Induced Electron Delocalization of Trifunctional Electrocatalysts for Rechargeable Zn–Air Batteries and Self‐Powered Water Splitting

AbstractThe development of low‐cost multifunctional electrocatalysts with high activity for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) is critical for the advancement of sophisticated energy conversion and storage devices. Herein, a trifunctional Ni(S0.51Se0.49)2@NC catalyst is designed and fabricated using a dianionic regulation strategy. Synchrotron radiation X‐ray absorption spectroscopy and density functional theory calculations reveal that simultaneous sulfidation and selenization can induce the electronic delocalization of Ni(S0.51Se0.49)2 active sites to enhance the adsorption of *OOH/*OH intermediate for ORR/OER and H* intermediate for HER. The OER and HER mechanisms are revealed by in situ Raman spectroscopy. The Ni(S0.51Se0.49)2@NC exhibits trifunctional catalytic activity for the HER (111 mV at 10 mA cm−2), OER (320 mV at 10 mA cm−2), and ORR (half‐wave potential of 0.83 V). The rechargeable zinc–air batteries (ZABs) exhibit an open‐circuit voltage of 1.46 V, a specific capacity of 799.1 mAh g−1, and excellent stability for 1000 cycles. The water electrolytic cell using Ni(S0.51Se0.49)2@NC electrodes delivers a current density of 10 mA cm−2 at a cell voltage of 1.59 V, and it can be powered using the constructed ZABs. These findings contribute to developing low‐cost and efficient non‐noble metal multifunctional catalysts.

Abundant Canadian pine with polysulfide redox mediating ZnS/CuS nanocomposite to attain high-capacity lithium sulfur battery

A new strategy is presented to immobilize the lithium polysulfides (LiPSs) and promote charge transfer kinetics at the S-electrode interface of lithium-sulfur (Li–S) batteries. In this work, biomass-derived porous carbonized pine (p-Cp), abundantly available in Canada, is used as the carbon host for S electrode in the Li–S batteries. A multifunctional composite electrocatalyst – zinc sulfide/copper sulfide (ZnS/CuS - ZCS) - is prepared through a simple chemical reaction involving successive immersion approach. The mesoporous p-Cp efficiently encapsulate the sulfur particles and provides sufficient pore volume to accommodate expansion/contraction of sulfur cathode during the charging-discharging processes. The nanostructured ZCS composite facilitates the liquid-solid phase conversion of lithium polysulfides (LiPSs) to Li2S to limit the LiPSs dissolution in the electrolyte. Our systematic investigation reveals that the CuS accelerates the electron transfer process while ZnS lowers the energy barrier for LiPSs redox kinetics in the composite electrode. Benefiting from the synergistic effect, the p-CpZCS/sulfur cathode achieves a high specific discharge capacity of about 1457 mAh g−1 at a rate of 0.1 C.

Structural transformation of molybdenum carbide with extensive active centers for superior hydrogen evolution

Mo2C-based materials are expected to be extraordinary electrocatalysts for hydrogen evolution reaction (HER) due to their unique Pt-like electronic structures. However, the strong interaction between Mo and H as well as the scarce active centers impede their further applications. Herein, a facile and controllable route via Zn doping is proposed to weaken the H adsorption energy of Mo and create more active centers to boost the HER kinetics. A series of hierarchical branched MoC/Mo2C catalysts with promoted HER kinetics are constructed and well controlled by Zn-doping, where the structural transformation from Mo2C to MoC give rise to the optimized electronic structure and attenuate H adsorption energy. Besides, all Zn and Mo sites in Zn-MoC/Mo2C catalyst can be activated, and thereby dramatically increase the number of active centers as well as enhance the intrinsic catalytic activity. As expected, the Zn-MoC/Mo2C catalyst exhibits extremely low overpotential and Tafel slopes with excellent durability in both alkaline and acidic solutions. This work highlights a feasible strategy for enhancing hydrogen generation by dopant induced structural transformation and might provide an avenue for low-cost, efficient, and multifunctional electrocatalysts.

Encapsulation of Fe-CoP with P, N-co-doped porous carbon matrix as a multifunctional catalyst for wide electrochemical applications

Hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) serve as the most promising electrochemical processes for renewable energy. Developing multifunctional electrocatalysts with high performance for HER, OER and ORR still remains a challenge. Herein, we report a facile method to prepare P, N-co-doped porous carbon encapsulated Fe-CoP (A-Fe-CoP/CPN) electrocatalyst through freeze drying, carbonization, and KOH activation. The acquired A-Fe-CoP/CPN possesses abundant pores with large surface area, which provides sufficient defect-rich sites for HER, OER, and ORR, in alkaline or acidic electrolytes. The A-Fe-CoP/CPN shows low overpotential and good stability for HER and OER in alkaline electrolyte. Density functional theory (DFT) computations reveal that the addition of Fe greatly facilitates the rate-determining step and overall catalytic pathway for both HER and OER. A-Fe-CoP/CPN also exhibits low half-wave potential (E1/2) for ORR, which indicates an enhanced performance than that of the noble Pt/C catalyst. Zn-air battery equipped with the A-Fe-CoP/CPN catalyst exhibits a high energy density (849 mAh g−1) and a long-time stability at 5 mA cm−2. This finding not only offers a facile strategy to prepare porous carbon materials with defect-rich sites, but also provides guidance for developing multifunctional electrocatalysts for wide electrochemical reactions.

Atomic ruthenium coordinated with chlorine and nitrogen as efficient and multifunctional electrocatalyst for overall water splitting and rechargeable zinc-air battery

Design and fabrication of multifunctional efficient and durable single-atom electrocatalyst is highly desirable and challenging for overall water splitting and zinc-air battery. Herein, a novel and efficient ruthenium coordinated with Cl and N single atom catalyst (Ru–Cl–N SAC) is synthesized. Electrochemical measurements disclose that the Ru–Cl–N SAC exhibits superior electrocatalytic activities toward hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) with long-term durability in alkaline medium. Furthermore, the overall water splitting cell requiring only 1.49 V to achieve a current density of 10 mA cm−2 and a rechargeable zinc-air battery with a specific capacity of 804.26 mAh g−1 and long-term durability for 360 h are fabricated based on the Ru–Cl–N SAC. The present work will pave the way for design and fabrication of novel and efficient multifunctional electrocatalysts in the realm of energy conversion and storage.

Theoretical investigation of HER/OER/ORR catalytic activity of single atom-decorated graphyne by DFT and comparative DOS analyses

Multifunctional catalysts for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) play a key role in the development of electrochemical energy systems. Moreover, single metal atoms embedded in a two-dimensional material substrate have emerged as outstanding catalysts. Owing to its large surface area and novel electronic properties, graphyne (GY) is a promising substrate for the fabrication of single-atom catalysts (SACs). By doping foreign atoms of different types on GY, their local electronic/chemical environment and catalytic performance would be improved. Based on recent experimental advances, we used density functional theory (DFT) simulations to identify a suitable series of co-decorated GY materials, with boron-, nitrogen-, phosphorus-, and sulfur-doped GY (3B-GY, 3N-GY, 3P-GY, 3S-GY) as the two-dimensional substrate, and transition metal (TM) atoms (Sc to Zn) as the single-atom centers. Our screening process showed that Co@GY and Ni@3B-GY would be highly promising multifunctional electrocatalysts for HER/OER/ORR. Then, we built quantitative structure–property relationship (QSPR) between electronic density of states (DOS) structure and catalytic performance using comparative DOS analysis (CoDOSA). The present results further support the development and application of d-band center theory. Our work identifies promising co-decorated GY for HER/OER/ORR and provides quantitative information on their DOS.

Heteroatom-Doped Carbon-Encapsulated FeP Nanostructure: A Multifunctional Electrocatalyst for Zinc-Air Battery and Water Electrolyzer.

The rational design and synthesis of efficient multifunctional electrocatalysts for renewable energy technologies is of significant interest. Herein, we demonstrate a novel approach for the synthesis of a nitrogen and phosphorus dual-doped mesoporous carbon-encapsulated iron phosphide (FeP@NPC) nanostructure and its multifunctional electrocatalytic activity toward an oxygen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction for zinc-air battery (ZAB) and alkaline water-splitting applications. FeP@NPC is obtained by the carbothermal reduction of the precursor complex [Fe(bpy)3](PF6)2 in the presence of melamine without any traditional phosphidating agent. The PF6- counteranion is used for the phosphidation of Fe. FeP@NPC obtained at 900 °C (FeP@NPC-900) exhibits excellent bifunctional oxygen electrocatalytic performance with a very low potential gap (ΔE = E1/2ORR - Ej10OER) of 670 mV. The ZAB device delivers a peak power density of 190.15 mW cm-2 (iR-corrected), specific capacity of 785 mA h gZn-1, and energy density of 706.5 Wh kgZn-1 at 50 mA cm-2. The ZAB exhibits excellent charge-discharge cycling stability for over 35 h with negligible voltaic efficiency loss (0.9%). Three CR2032 coin-cell-based ZABs made of an FeP@NPC-900 air cathode connected in series power 81 LEDs for 15 min. FeP@NPC-900 also has promising electrocatalytic activity toward water splitting in acidic as well as in alkaline pH. The benchmark current density of 10 mA cm-2 is achieved with a two-electrode alkaline water electrolyzer at a cell voltage of 1.65 V. ZAB-powered water electrolyzer is made by integrating two rechargeable ZABs connected in series with the two-electrode water electrolyzer. The ZAB powers the electrolyzer for 24 h without a significant loss in the open-circuit voltage. The catalyst retains its initial structural integrity even after continuous water electrolysis for 24 h.

Toward enhanced alkaline hydrogen electrocatalysis with transition metal-functionalized nitrogen-doped carbon supports

Superior catalyst supports are crucial to developing advanced electrocatalysts toward heterogeneous catalytic reactions. Herein, we systematically investigate the role of transition metal-functionalized N-doped carbon nanosheets (M-N-C, M = Mn, Fe, Co, Ni, Cu, Mo, and Ag) as the multifunctional electrocatalyst supports toward hydrogen evolution/oxidation reactions (HER/HOR) in alkaline media. The results demonstrate that all the M-N-C nanosheets, except Cu-N-C and Ag-N-C, can promote the alkaline HER/HOR electrocatalytic activity of Pt by accelerating the sluggish Volmer step, among which Mn plays a more significant role. Analyses reveal that the promotion effect of M-N-C support is closely associated with the electronegativity of the metal dopants and the relative filling degree of their d-orbitals. For one, the metal dopant in M-N-C with smaller electronegativity would provide more electrons to oxygen and hence tune the electronic structure of Pt via the M-O-Pt bonds at the interface. For another, the transition metal in M-N4 moieties with more empty d orbitals would hybridize with O 2p orbitals more strongly that promotes the adsorption of water/hydroxyl species. The results demonstrate the conceptual significance of multifunctional supports and would inspire the future development of advanced electrocatalysts.

Sea urchin-like NiMoO4 nanorod arrays as highly efficient bifunctional catalysts for electrocatalytic/photovoltage-driven urea electrolysis

Developing multifunctional electrocatalysts with high catalytic activity, long-term stability, and low cost is essential for electrocatalytic energy conversion. Herein, sea urchin-like NiMoO4 nanorod arrays grown on nickel foam has been developed as a bifunctional electrocatalyst for urea oxidation and hydrogen evolution. The NiMoO4-200/NF catalyst exhibits efficient activity toward hydrogen evolution reaction with a low overpotential of only 68 mV in 1.0 mol/L KOH to gain a current density of 10 mA cm–2. The NiMoO4-300/NF catalyst exhibits a prominent oxygen evolution reaction (OER) catalytic activity with an overpotential of 288 mV at 50 mA cm–2, as well as for urea oxidation reaction with an ultra-low potential of 1.36 V at 10 mA cm–2. The observed difference in electrocatalytic activity and selectivity, derived by temperature variation, is ascribed to different lattice oxygen contents. The lattice oxygen of NiMoO4-300/NF is more than that of NiMoO4-200/NF, and the lattice oxygen is conducive to the progress of OER. A urea electrolyzer was assembled with NiMoO4-200/NF and NiMoO4-300/NF as cathode and anode respectively, delivering a current density of 10 mA cm–2 at a cell voltage of merely 1.38 V. The NiMoO4 nanorod arrays has also been successfully applied for photovoltage-driven urea electrolysis and hydrogen production, revealing its great potential for solar-driven energy conversion.

Cation modulation in dual-phase nickel sulfide nanospheres by pulsed laser irradiation for overall water splitting and methanol oxidation reaction

The development of a non-precious and highly active multifunctional electrocatalyst is essential for obtaining efficient electrochemical energy storage and conversion devices. Nickel derivate occupies the most important place when it comes to the transition metal-based electrocatalyst. In this study, we used a simple and extremely effective controllable pulsed laser irradiation (PLI) technique to fabricate dual-phase nickel sulfide, and we studied cation modulation using Co and Cu atoms. The multifunctional activity was witnessed by the performances of oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and methanol oxidation reaction (MOR) measured in an alkaline medium. The cation adjustment resulted in the improvement of the catalytic performance of HER and OER during Cu and Co substitution, respectively. For the Co-Ni-S sample in OER, we achieved an overpotential of 368 mV at 10 mA/cm2 in OER. The higher ECSA Cu-Ni-S sample improved HER activity at a lower overpotential of 271 mV at 10 mA/cm2 and a lower Tafel slope of 98 mV/dec. The excellent bifunctional activity enhanced overall water splitting with a lower voltage of 1.88 V to achieve a geometrical current density of 10 mA/cm2, with high durability. Meanwhile, the high selectivity of Cu resulted in a very high methanol electrooxidation activity with a current density as high as 55.4 mA/cm2. The detailed electrochemical studies were presented with their supporting physiochemical analysis. This report shows the efficiency and simplicity of fabricating transition metal derivatives and cation modulation using superficial laser methods.

WS2@Co9S8@N/C core–shell as multifunctional electrocatalysts for dye-sensitized solar cell, oxygen reduction reaction and oxygen evolution reaction

WS2@Co9S8@N/C core–shell as multifunctional electrocatalysts for dye-sensitized solar cell, oxygen reduction reaction and oxygen evolution reaction

Electrospinning construction of heterostructural Co3W3C/CoP nanoparticles embedded in N, P-doped hierarchically porous carbon fibers as excellent multifunctional electrocatalyst for Zn-air batteries and water splitting

A series of heterostructural Co 3 W 3 C/CoP nanoparticles embedded in N, P-doped hierarchically porous carbon fibers were fabricated facilely as excellent multifunctional electrocatalysts. The optimal sample CoWCP-NPC-2:1 exhibited highly efficient catalytic activities for HER, OER, ORR, overall water splitting and Zn-air batteries. • The preparing procedure is simple. • The interfacial engineering is employed. • Synergistic effect beween the muti-composition has been shown. • The catalysts show excellent multifunctional performances on ORR, OER and HER. • Broad application prospects in Zn–air batteries and water electrolysis are expected. In this work, facile electrospinning method has been adopted to construct the interfacial engineering heterostructures of Co 3 W 3 C/CoP nanoparticles embedded in N, P-doped hierarchically porous carbon fibers, in which abundant interfaces and multiple active sites were formed. The fabricated catalysts Co 3 W 3 C/CoP/NPC have shown prominent trifunctional electrocatalytic activities for hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), evidenced by a positive half-wave potential of 0.803 V for ORR and a much low overpotential (at 10 mA/cm 2 ) of 139/200 mV for HER and OER in alkaline electrolyte, respectively. Furthermore, the rechargeable zinc-air battery based on the optimum CoWCP-NPC-2:1 catalyst has shown a prominent high power density of 205.5 mW/cm 2 and a specific capacity of 800.5 mAh·g −1 after 83.5 h/501 cycles at 10 mA/cm 2 . When the catalyst CoWCP-NPC-2:1 was employed as anode and cathode electrocatalysts for overall water splitting, only 1.49 V of cell voltage was needed to reach 10 mA/cm 2 . This work will provide inspiration for the design of advanced, multifunctional, and performance-oriented heterogeneous catalysts in sustainable energy conversion technology.

Integrated CoPt electrocatalyst combined with upgrading anodic reaction to boost hydrogen evolution reaction

Exploiting highly effective and low-cost electrocatalyst for water splitting is an instant challenge for the development of sustainable hydrogen energy. In this work, we report an integrated bifunctional electrocatalyst composed of CoPt nanoparticles uniformly distributed on the carbon nanosheet array (CNs@CoPt), which exhibits excellent activity for both cathodic hydrogen evolution in a wide range of pH conditions and anodic glycerol oxidation reaction. Based on this novel electrocatalyst, a hydrogen evolution coupled with glycerol oxidation system was constructed, exhibiting dramatically enhanced hydrogen production rate (48 L h−1 m−2) in cathode, larger than traditional water splitting system (27 L h−1 m−2), and gaining high-valuable product (formate, 113 g h−1 m−2) in anode. Moreover, a quite high utilization degree of Pt (35.1%) is achieved on CNs@CoPt owing to this hierarchical and alloy structure, 3.3 times higher than that of commercial Pt/C (10.6 %). We believe that the strategy demonstrated in this work can be extended to fabricate other multifunctional integrated electrocatalysts with high performance for hydrogen production.

Interfacial electronic engineering of Ru/FeRu nanoparticles as efficient trifunctional electrocatalyst for overall water splitting and Zn-air battery

Rational design of multi-functional electrocatalyst for hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is critical to energy conversion and storage technologies such as water splitting and metal-air batteries. However, explorations of specific interface structures for catalysts are still limited and challenging. Herein, a novel core–shell architecture comprising of Ru and FeRu hybrid enwrapped with a carbon shell anchored on nitrogen-doped carbon substrate (Ru-FeRu@C/NC) was constructed. Specifically, the interfacial electronic interaction between Ru and FeRu regulate the electron configuration and broaden the electron transfer pathway to boost its electrocatalytic performance. Particularly, Ru-FeRu@C/NC required ultralow overpotentials of 23 and 345 mV to drive a current density of 10 mA cm−2 for HER and OER, respectively, and a positive half-wave potential of 0.90 V versus reversible hydrogen electrode (RHE) for ORR. Furthermore, an electrocatalytic water splitting cell powered by a Zn–air battery was successfully fabricated using Ru-FeRu@C/NC as the “one-in-all” electrocatalyst. The present work paves the way for design and construction of efficient multifunctional electrocatalyst in energy conversion and storage.

Highly ordered nanoarrays catalysts embedded in carbon nanotubes as highly efficient and robust air electrode for flexible solid-state rechargeable zinc-air batteries

The development of multicomponent materials is the most efficient and successful way for creating advanced multifunctional catalysts. Herein, the bimetal FeCo nanoarrays enclosed N-CNTs have a high surface on carbon cloth support, which promotes efficient electron transport and prevents nanoparticle aggregation. Taking advantage of the high-level use of active material and fast charge transfer, the developed electrocatalyst exhibits excellent multifunctional electrocatalyst such as oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The N-CNTs@MOF FeCo nanoarrays @CC exhibit higher activity than reference catalysts including MOF FeCo nanoarrays@CC, FeCo nanoarrays@CC, and CC. Interestingly, the synthesized multifunctional catalyst, which serves as the air electrode in zinc-air batteries with liquid electrolytes as well as solid-state gel electrolytes possesses outstanding charging-discharge performance and long service life. This study provides enormous potential for the real implementation of portable, even wearable, and efficient rechargeable batteries in the future.

Defect-enriched heterointerfaces N–MoO2–Mo2C supported Pd nanocomposite as a novel multifunctional electrocatalyst for oxygen reduction reaction and overall water splitting

Developing highly efficient, cost-saving, and durable multifunctional electrocatalysts for oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) continues to be a significant challenge in the energy field. In this work, we decide to prepare an unusual multifunctional electrocatalyst, such as icosahedral palladium nanocrystals (PdNCs) encapsulating on N–MoO2–Mo2C half-hollow nanotube (HHNT) heterointerface, using an in-situ chemical reaction and following sonic probe irradiation method. All the experiments demonstrate that special defect-enriched heterointerfaces N–MoO2–Mo2C supported Pd nanocomposite can greatly improve the ORR activity (Eonset = 1.01 V and E1/2 = 0.90 V) with good stability, outstanding HER (η10 = 65 mV) and OER (η10 = 180 mV) performances than those of commercial precious electrocatalysts (Platinum on carbon [Pt/C] and ruthenium oxide [RuO2]). The overall water splitting electrolyzer fabricates by Pd/N–MoO2–Mo2C as both anode and cathode electrodes to achieve a current density of 10 Ma/cm2 at a cell voltage of 1.56 V, which surpasses the most recent reported electrocatalysts.

Interfacial coupling porous cobalt nitride nanosheets array with N-doped carbon as robust trifunctional electrocatalysts for water splitting and Zn-air battery

Compositional and structural engineering of high-performance catalysts is vital for electrochemical catalysis, but challenges remain in their facile synthesis and efficient controls. Herein, a novel vaporization-nitridation synthesis strategy with simple operation is developed to prepare hierarchically porous cobalt nitride hybrid nanosheets grown on Ni foam by coupling cobalt nitride with N-doped carbon (CoN@NC). Benefitting from the highly open 3D hierarchical porous architecture and strong coupling effect between CoN and NC, the obtained CoN@NC electrode possesses accelerated ion and electron transfer. Moreover, the transform from CoN to CoOOH during water oxidation is confirmed by in-situ Raman characterizations, which together with NC and CoN species afford multiple active sites. The optimized CoN@NC-300 exhibits remarkable trifunctional catalytic activity towards OER, HER and ORR. Consequently, a two-electrode electrolyzer based on CoN@NC-300 needs only a voltage of 1.53 V to achieve the current density of 10 mA cm−2. Moreover, the flexible Zn-air battery assembled with CoN@NC exhibits high performance and superior durability. This work offers a novel method for designing metal nitride hybrids as highly efficient multifunctional electrocatalysts towards electrocatalysis and energy storage.

Trilayer Metal-Organic Frameworks as Multifunctional Electrocatalysts for Energy Conversion and Storage Applications.

The need for enhanced energy storage and improved catalysts has led researchers to explore advanced functional materials for sustainable energy production and storage. Herein, we demonstrate a reductive electrosynthesis approach to prepare a layer-by-layer (LbL) assembled trimetallic Fe-Co-Ni metal-organic framework (MOF) in which the metal cations within each layer or at the interface of the two layers are linked to one another by bridging 2-amino-1,4-benzenedicarboxylic acid linkers. Tailoring catalytically active sites in an LbL fashion affords a highly porous material that exhibits excellent trifunctional electrocatalytic activities toward the hydrogen evolution reaction (ηj=10 = 116 mV), oxygen evolution reaction (ηj=10 = 254 mV), as well as oxygen reduction reaction (half-wave potential = 0.75 V vs reference hydrogen electrode) in alkaline solutions. The dispersion-corrected density functional theory calculations suggest that the prominent catalytic activity of the LbL MOF toward the HER, OER, and ORR is due to the initial negative adsorption energy of water on the metal nodes and the elongated O-H bond length of the H2O molecule. The Fe-Co-Ni MOF-based Zn-air battery exhibits a remarkable energy storage performance and excellent cycling stability of over 700 cycles that outperform the commercial noble metal benchmarks. When assembled in an asymmetric device configuration, the activated carbon||Fe-Co-Ni MOF supercapacitor provides a superb specific energy and a power of up to 56.2 W h kg-1 and 42.2 kW kg-1, respectively. This work offers not only a novel approach to prepare an LbL assembled multimetallic MOF but also provides a benchmark for a multifunctional electrocatalyst for water splitting and Zn-air batteries.