Stable Bifunctional Electrocatalysts Research Articles

Designing bifunctional perovskite catalysts for the oxygen reduction and evolution reactions.

The development of unified regenerative fuel cells (URFCs) necessitates an active and stable bifunctional oxygen electrocatalyst. The unique challenge of possessing high activity for both the oxygen reduction (ORR) and oxygen evolution (OER) reactions, while maintaining stability over a wide potential window impedes the design of bifunctional oxygen electrocatalysts. Herein, two design strategies are explored to optimize their performance. The first incorporates active sites for the ORR and OER, Mn and Co, into a single perovskite structure, which is achieved with the perovskites Ba0.5Sr0.5Co0.8Mn0.2O3-δ (BSCM) and La0.5Ba0.25Sr0.25Co0.5Mn0.5O3-δ (LBSCM). The second combines an active ORR perovskite catalyst (La0.4Sr0.6MnO3-δ (LSM)) with an OER active perovskite catalyst (Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF)) in a physical mixed composite (BSCF/LSM). The success of the two strategies is investigated by measuring the catalysts' catalytic performance and response to alternating reducing and oxidizing potentials to mimic the dynamic conditions experienced during the operation of URFCs. Additionally, the continuous, potentiodynamic change in Mn, Co, and Fe oxidation states during the ORR and OER is elucidated with operando X-ray absorption spectroscopy (XAS) measurements, revealing key insights into the nature of the active sites. The results reveal important catalyst physiochemical properties and provide a guide for future research and design principles for bifunctional oxygen electrocatalysts.

Cr-doped CoFe2O4 nanorod array modified by oxygen vacancy-rich cerium oxide as an efficient bifunctional total water splitting catalyst

Highly efficient and stable bifunctional electrocatalysts for total water splitting are crucial for the realization of large-scale hydrogen production. In this study, we successfully synthesized CeOx-modified CoCryFe2-yO4 nanorod array structures...

Metal-Oxygen Covalency Competition of Unsymmetrical Metal Pairs for Enhanced Bifunctional Oxygen Electrocatalysis

Rechargeable zinc-air batteries are considered promising energy conversion devices due to their inherent safety and high energy-to-cost ratio. However, the sluggish kinetics of oxygen evolution reaction and oxygen reduction reaction during the charging-discharging process lead to low round trip efficiency and power density. The synthesis of efficient and stable bifunctional oxygen electrocatalysts constitutes the bottleneck to construct applicable ZABs.Here, we report an Mn-doped ruthenium oxide electrocatalyst that exhibits remarkable ORR/OER activity, with a low potential gap of 0.62V between the half-wave potential of ORR and the OER potential at 10mA cm-2. The Mn-RuO2 assembled ZABs present a high power density of 179 mW cm-2 and long lifespans of 800 h. Metal covalency competition induces surface Mn atoms shows more favorable adsorption behavior for ORR and Ru atoms shows more favorable adsorption behavior for OER. The charge redistribution between asymmetrical Ru-O-Mn pairs results in dual actives sites towards OER/ORR. The surface ruthenium stabilizes the O* intermediate due to the weaker hybridization of the lattice Ru-O bond. The upshift of the dz2 orbital relieves the over-binding of the critical intermediates OH* on the Mn atom. Such dual Ru-Mn sites minimized the OER/ORR activity gap restricted by scaling relationships. Our findings rationalize the double active sites mechanism in Mn-RuO2 electrocatalyst and provide a strategy to enhance bifunctional catalytic performance. Figure 1

NiSe2 nanosheets with electronic structure regulated by Mo-doping as an efficient bifunctional electrocatalyst for overall water splitting

Developing low-cost, highly efficient and stable bifunctional electrocatalysts for overall water splitting is vital but still a challenge. Hetero-atom doping is an effective strategy to improve the catalytic activity of electrocatalysts by increasing active sites and regulating electronic structure. Here, Mo-doped NiSe2 nanosheets were in situ grown on nickel foam (NF) by hydrothermal and the subsequent selenization process as bifunctional electrocatalysts for overall water splitting. Incorporation of Mo into NiSe2 can regulate the electronic structure, increase the numbers of high-valence Ni3+ and active sites, generate the disorder defects due to the formation of active material NiOOH, and decrease the charge transfer resistance. The above synergistic roles make the Mo-doped NiSe2 to present superior catalytic performances and remarkable stability for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Under alkaline condition, the overpotentials of OER and HER are 210 mV and 172 mV at a current density of 10 mA cm–2, respectively. Moreover, only a low cell voltage of 1.57 V is required to reach a current density of 10 mA cm–2 in a water splitting device assembled with the Mo-doped NiSe2 as the anode and cathode. Therefore, this study opens up a new way for designing non-precious bifunctional electrocatalysts by Mo doping.

Highly stable Ru nanoparticles anchored on NiFe layered double hydroxides as efficient water splitting electrocatalysts

Developing efficient and stable bifunctional electrocatalysts is highly desirable for boosting the energy efficiency of water splitting. Herein, we propose an effective ruthenium nanoparticle anchoring approach to reconstruct NiFe LDH including the customized morphology and configuration of active species. The synthesized NiFe LDH-Ru shows an excellent HER and OER performance with low overpotentials of 52 and 217 mV at 10 mA cm−2, respectively, which exceeds most of the existing HER and OER catalysts. Moreover, the NiFe LDH-Ru catalyst also presents excellent long-term stability. This work provides a new approach for exploring efficient electrocatalysts for clean and renewable energy applications.

Constructing defect-rich S-doped NiMoO4/Ni3S2 2D/2D heterostructures as highly efficient and stable bifunctional electrocatalysts for overall water splitting

The development of economical, efficient, and durable bifunctional catalyst for overall water splitting is an attractive and challenging task. Herein, a novel defect-rich 2D/2D heterostructure is constructed by vertically growing S-doped NiMoO4 (NiMoO4-S) nanosheets on nickel sulfide (Ni3S2) nanosheet arrays supported on nickel foam (NF) using a two-step hydrothermal method. Benefiting from the hierarchical sheet-on-sheet heterogeneous nanostructure and abundant oxygen vacancies for more active sites, efficient electronic/mass transfer, and fast gas release, the synthesized NiMoO4-S/Ni3S2/NF electrode exhibits excellent electrocatalytic performance for HER (η10 mA cm−2 = 107 mV) and OER (η50 mA cm−2 = 285 mV). The alkaline water electrolyzer with NiMoO4-S/Ni3S2/NF as the positive and negative electrodes can provide a current density of 10 mA cm−2 with the potential of 1.52 V, which is below that of the commercial Pt||RuO2/NF system or many other reported systems. More importantly, the alkaline water electrolyzer offers a current density of 100 mA cm−2 at 1.85 V with outstanding durability of over 50 h. This research points to a promising route in designing transition metal-based bifunctional electrocatalysts for large-scale energy conversion applications.

Bubble-template assisted fast electrochemical deposition of 3-D ternary Ni-Cu-Co alloy as promising catalyst for electrochemical overall water splitting

Today, the synthesis of electrocatalysts with excellent and unique activity for hydrogen production is one of the most critical challenges. In this study, binder-free and active Ni-Cu-Co electrode was created by electrochemical preparation manner. Its electrocatalytic behavior was investigated for hydrogen evolution reaction (HER), and oxygen evolution reaction (OER). The electrocatalytic activity was investigated by linear sweep voltammetry (LSV), cyclic voltammetry (CV), Tafel and electrochemical impedance spectroscopy (EIS) tests. The results of the electrocatalytic behavior showed that the Ni-Cu-Co 3-D electrode fabricated at 3 A·cm−2 inspired by high active surface area, having superhydrophilic nature and synergistic effect between elements, has the best hydrogen production performance. The needed overpotential for 10 mA.cm−2 was only 68 mV and 245 mV in HER and OER, respectively. In addition, in the overall water splitting cell using this electrode as a cathode and anode, the 10 mA.cm−2 current density will attain in 1.55 V with outstanding stability. This study, introduces the new fast electrochemical method for synthesizing an active and stable bi-functional electrocatalyst.

Interfacial engineering of nickel selenide with CeO2 on N-doped carbon nanosheets for efficient methanol and urea electro-oxidation

The design of low cost, high efficiency electrocatalysts for methanol oxidation reactions (MOR) and urea oxidation reactions (UOR) is a pressing need to address the energy crisis and water pollution. In the present work, we developed Cerium dioxide (CeO2) and nickel selenide (Ni0.85Se) nanoparticles integrated into three-dimensional N-doped carbon nanosheets to be used as efficient and stable bifunctional electrocatalysts for MOR and UOR. By optimizing the selenization temperature, the CeO2-modified Ni0.85Se obtained at selenization temperature of 550 °C (CeO2-Ni0.85Se-550-NC) has the best MOR and UOR electrochemical performance. The CeO2-Ni0.85Se-550-NC potential only requires 1.309 V (MOR) and 1.294 V (UOR) to reach 10 mA cm−2, respectively. The DFT study reveals that CeO2-Ni0.85Se-550-NC has the best reaction path with the synergistic effect between CeO2 and Ni0.85Se. The outstanding catalytic performance of CeO2-Ni0.85Se-550-NC may be due to the cointeraction between CeO2 and Ni0.85Se, allowing more defects that function as catalytic sites while promoting fast electron transfer in the N-doped carbon substrate.

Facile Synthesis of Co Nanoparticles Embedded in N-Doped Carbon Nanotubes/Graphitic Nanosheets as Bifunctional Electrocatalysts for Electrocatalytic Water Splitting.

Developing robust and cost-effective electrocatalysts to boost hydrogen evolution reactions (HERs) and oxygen evolution reactions (OERs) is crucially important to electrocatalytic water splitting. Herein, bifunctional electrocatalysts, by coupling Co nanoparticles and N-doped carbon nanotubes/graphitic nanosheets (Co@NCNTs/NG), were successfully synthesized via facile high-temperature pyrolysis and evaluated for water splitting. The morphology and particle size of products were influenced by the precursor type of the cobalt source (cobalt oxide or cobalt nitrate). The pyrolysis product prepared using cobalt oxide as a cobalt source (Co@NCNTs/NG-1) exhibited the smaller particle size and higher specific surface area than that of the pyrolysis products prepared using cobalt nitrate as a cobalt source (Co@NCNTs/NG-2). Notably, Co@NCNTs/NG-1 displayed much lower potential -0.222 V vs. RHE for HER and 1.547 V vs. RHE for OER at the benchmark current density of 10 mA cm-2 than that of Co@NCNTs/NG-2, which indicates the higher bifunctional catalytic activities of Co@NCNTs/NG-1. The water-splitting device using Co@NCNTs/NG-1 as both an anode and cathode demonstrated a potential of 1.92 V to attain 10 mA cm-2 with outstanding stability for 100 h. This work provides a facile pyrolysis strategy to explore highly efficient and stable bifunctional electrocatalysts for water splitting.

Unveiling the Structural Self-Reconstruction and Identifying the Reactive Center of a V, Fe Co-Doped Cobalt Precatalyst toward Enhanced Overall Water Splitting by Operando Raman Spectroscopy.

The development of efficient and stable bifunctional electrocatalysts based on non-noble metals for water electrolysis is both urgent and challenging. However, unresolved issues remain regarding the challenge of identifying the active phase and gaining a comprehensive understanding of its surface reconstruction and functionality throughout the reaction process. In this study, we have combined doping and heterostructure construction by a one-step electrodeposition and a subsequent activation treatment to synthesize Fe, V co-doped Co3O4/Co(OH)2 and Co/Co(OH)2 heterointerfaces (referred to as A-Co60Fe1.1V). These heterointerfaces, composed of Co/Co(OH)2 and Co3O4/Co(OH)2, are proposed to facilitate charge transfer process during catalysis. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the introduction of V and Fe dopants increases the valence state of Co centers in Co3O4 and Co(OH)2. Further operando Raman spectroscopy reveals that Co(OH)2 and Co3O4 with the high-valence Co centers remain stable during the hydrogen evolution reaction (HER) process. These high-valence Co centers are believed to promote the crucial water dissociation step and therefore enhance the overall HER catalysis. On the other hand, during the oxygen evolution reaction (OER), Fe, V co-doping leads to an earlier formation of the active CoOOH species, while Fe doping can further help stabilize the more reactive β-CoOOH species instead of the less reactive γ-CoOOH. As a result, the A-Co60Fe1.1V catalyst exhibits significantly improved catalytic activity for both HER and OER that it requires low overpotentials of 51 and 250 mV, respectively, to attain a current density of 10 mA cm-2. Moreover, when utilized as both the cathode and anode in alkaline water electrolysis, the A-Co60Fe1.1V catalyst can operate at a mere 1.54 V voltage while maintaining 10 mA cm-2, surpassing the majority of non-noble metal catalysts. Remarkably, it also exhibits stability for at least 40 h at ∼100 mA cm-2.

Zinc-Substituted Cobalt Phosphate [ZnCo2(PO4)2] as a Bifunctional Electrocatalyst.

Development of highly efficient, earth-abundant, and stable bifunctional electrocatalysts is pivotal for designing viable next-generation metal-air batteries. Cobalt-based phosphates provide a treasure house to design electrocatalysts, with a wide range of cation substitutions to further enhance their electrocatalytic activity. In particular, phosphates with distorted geometry show favorable binding efficiency toward water molecules with low overpotential. In the present work, zinc-substituted cobalt phosphate ZnCo2(PO4)2 was investigated. Its crystal structure was solved to a monoclinic framework built with CoO6 octahedra and distorted CoO5/ZnO5 trigonal bipyramid leading to efficient bifunctional electrocatalytic activity. It offers robust structural stability with onset potential values of 0.87 V (vs reversible hydrogen electrode (RHE)) and 1.50 V (vs RHE) for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes, respectively, comparable to the precious metal catalysts. The origin and stability of the bifunctional activity were probed by combining ex situ diffraction and electron microscopy corroborated by ab initio calculations. Overall, zinc-substituted cobalt phosphate [ZnCo2(PO4)2] forms a potential bifunctional electrocatalyst with tunable local cobalt coordination that can be harnessed for metal-air batteries.

Rational Design of Goethite-Sulfide Nanowire Heterojunctions for High Current Density Water Splitting.

The preparation of efficient and stable bifunctional electrocatalysts for electrochemical overall water splitting (OWS) to scale up commercial hydrogen production remains a great challenge. Here, we synthesized heterojunction structures consisting of Co9S8/Ni3S2 nanowire arrays and amorphous goethite (FeOOH, α-phase) particles as efficient OWS catalysts using an interface engineering strategy. The interfacial charge inhomogeneity caused by the heterojunction contact leads to the generation of a built-in electric field, which makes the electron-deficient FeOOH and electron-rich Co9S8/Ni3S2 favorable for hydrogen/oxygen evolution reaction, respectively, thus ensuring the excellent activity of FeOOH/Co9S8/Ni3S2 as a bifunctional catalyst. FeOOH/Co9S8/Ni3S2 exhibits impressive catalytic activity for the oxygen evolution reaction, achieving an ultralarge current density of 1000 mA cm-2 needed as low as 265 mV overpotential, and its stability was tested up to 1440 h. Furthermore, an excellent OWS output (1.55 V to generate 10 mA cm-2) is achieved by the bifunctional FeOOH/Co9S8/Ni3S2 catalysts.

An ultra-high electrochemical performance of surface-rich boron induced multi-metal centered heterocatalyst for overall water splitting

Preparing highly active and stable bifunctional electrocatalyst for hydrogen evolution and oxygen evolution reactions (HER/OER) in alkaline conditions is essential to reducing energy losses in the water-alkali industry but challenging undertaking. A simple room-temperature boronization approach is projected to fabricate boronated CuCo2O4/NiO nanoarrays for bifunctional catalytic activities. Herein, a modest hydrothermal process is applied to cultivate heterostructure CuCo2O4/NiO nanoarrays by spanning ternary metal (Cu–Co–Ni) oxides followed by a boronization strategy on a self-supporting nickel foam substrate. The outcome of the experiment revealed that ultra-surface optimization with boron permits accelerated electron transfer and multiplies the access of surface coordinative unsaturated active sites. As a result, B–CuCo2O4/NiO nanoarrays supported on nickel foam (NF) require fewer overpotentials of 52 mV for the hydrogen evolution reaction and 294 mV for the oxygen evolution reaction to achieve a current density of 20 mA cm−2. Surprisingly, employing B–CuCo2O4/NiO@NF as a bifunctional electrocatalyst for overall water splitting empowers an alkaline electrolyzer with a current density of 10 mA cm−2 and a cell voltage of 1.54 V. The current study could pave the groundwork for the rise of boron-induced Cu–Co–Ni oxides hetero-assemblies for electrocatalysis.

Modulation of the morphology, composition, and oxidation state of the spinel high-entropy oxides to boost their bifunctional catalytic activity for overall water splitting

Developing efficient, cheap, and stable bi-functional electrocatalysts is one of the most important keys to solve the current energy and environment issues. In this thesis, a novel high-entropy oxide (HEO) with special morphology is synthesized. Our results showed that the introduction of F− will effectually improve the morphology of the material. The 3D macro-flowers assembled through a series of nano-sheets increase the specific area of the materials obviously and thus offer more active sites for the catalytic reactions, being beneficial for the overall water splitting performance. Furthermore, the incorporation of well-behavior Zn and Cu elements and the non-equilibrium F− dopants results in a charge redistributions of the active metal sites, which are not fixed at a specific oxidation state but adaptable at (2±δ)+ or (3±δ)+. This unique synergistic effect among multiple metal ions will facilitate the HER and OER performance of the catalysts simultaneously. As a result, HEO-F-30 sample exhibit the overpotentials of 67 mV and 245 mV respectively for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) under alkaline environment. In addition, the bi-functional electrode made by HEO-F-30 catalyst can realized the overall water decomposition at 1.65 V at 10 mA cm−2. This study states a useful tactic to modulate the morphology and the synergetic effect of the HEOs to optimize their overall water splitting performance.

Highly accessible atomically dispersed FeNx sites coupled with Fe3C@C core-shell nanoparticles boost the oxygen catalysis for ultra-stable rechargeable Zn-air batteries

It is significant but challenging to develop a cost-effective, high-efficiency, and stable bifunctional electrocatalyst of oxygen reduction and evolution reactions (ORR and OER) for rechargeable Zn-air batteries. Herein, we present a novel bifunctional catalyst constructed by highly accessible atomically dispersed MNx sites coupled with core-shell nanoparticles (M-Phen-800; M = Fe, Co, and Ni) from easily accessible M-Phenanthroline (M-Phen) complexes. Due to the synergistically induced symmetric charge distribution around FeNx sites by Fe3C@C core-shell nanoparticles, Fe-Phen-800 exhibits exceptional onset (Eonset = 0.994 V) and half-wave (E1/2 = 0.878 V) potentials for ORR and a very low overpotential of 285 mV @ 10 mA cm−2 (Ej=10) for OER, indicating excellent bifunctional activity (ΔE = Ej=10 - E1/2 = 0.637 V) over the state-of-the-art Pt/C-RuO2 (0.702 V) combination. Moreover, the Fe-Phen-800-based Zn-air battery demonstrates a remarkable energy density of 1022 Wh kg−1 and greater cycling stability (>800 cycles) than the commercial Pt/C-RuO2 battery.

NaCl sealing Strategy-Assisted synthesis CoO-Co heterojunctions as efficient oxygen electrocatalysts for Zn air batteries

Developing highly efficient, low-cost, and stable bifunctional oxygen electrocatalysts is essential for the wide popularization of rechargeable Zn-air batteries. Combining zero-dimensional metal nanoparticles with two-dimensional metal oxide nanosheets is an appealing strategy to balance performance and cost. However, the precise construction of these composites remains a great challenge, and their interaction mechanisms lack thorough study. Herein, a cobalt-oxide-based bifunctional oxygen electrocatalyst comprising a rich Co-CoO heterointerface (CoO/Co@NG) was synthesized via a NaCl sealing-assisted pyrolysis strategy. The NaCl crystals played the role of a closed nanoreactor, which facilitated the formation of a CoO-Co heterojunction. Experimental results and theoretical calculations confirmed that the ingeniously constructed heterojunction expedited the oxygen reduction reaction and oxygen evolution reaction kinetics, which is superior to Pt/C. When serving as the air electrode in an assembled liquid-state Zn-air battery, the battery shows high power density (215 mW cm−2), specific capacity (710 mAh gzn−1), and outstanding durability (720 h at 10 mA cm−2). This work provides an innovative avenue to design high-performance heterojunction electrocatalysts for perdurable Zn-air batteries.

Metal-organic frameworks stabilized Mo and W binary single-atom catalysts as high performance bifunctional electrocatalysts for water electrolysis

Single atom catalysts (SACs) are commonly composed of single atoms (SAs) anchored on relatively inert supports containing surface heteroatoms, leading to low specific catalytic efficiency. A new SAC design strategy, anchoring SAs on catalytically active porous supports, was proposed and demonstrated with NiFe-based metal-organic frameworks (MOFs) stabilized Mo and W binary SACs, MOF-MoSAWSA, as highly efficient and stable bifunctional electrocatalysts for electrolytic water splitting. MOF-MoSAWSA delivered current densities of 10 and 500 mA cm−2 at ultralow overpotentials of 199 and 250 mV for oxygen evolution reaction and at decent overpotentials of 57 and 297 mV for hydrogen evolution reaction, respectively. For overall water splitting, the MOF-MoSAWSA//MOF-MoSAWSA couple achieved ultralow cell voltages of 1.501 and 1.780 V to deliver current densities of 10 and 500 mA cm−2, respectively, and exhibited excellent stability with only 2% decay in current densities after a 56-hour operation at an ultrahigh initial current density of 515 mA cm−2. The success was attributed to the positive synergy between the SAs and MOF and between Mo and W SAs, as revealed with X-ray absorption and photoelectron spectroscopic analyses. The present development offers a new route for fabrication of advanced SA based catalysts.

Coupling heterostructured CoP-NiCoP nanopin arrays with MXene (Ti3C2Tx) as an efficient bifunctional electrocatalyst for overall water splitting

Developing a highly effective bifunctional electrocatalyst for alkaline-condition electrochemical water splitting is both essential and challenging. The work presented here successfully synthesizes and employs a heterostructured CoP-NiCoP ultra-long nanopin array in situ growing on MXene (Ti3C2Tx) as a stable bifunctional electrocatalyst for electrochemical water-splitting. The heterogeneous structure formed by CoP nanoparticles and NiCoP nanopins provides extra active sites for water-splitting. Also, Ti3C2Tx works as a support substrate during electrochemical operations, accelerating mass transfer, ion transport, and rapid gas product diffusion. Meanwhile, throughout the catalytic process, the dense nanopin arrays shield Ti3C2Tx from further oxidation. At a result, the CoP-NiCoP-Ti3C2Tx (denoted as CP-NCP-T) demonstrated excellent catalytic activity, with overpotentials of just 46 mV for hydrogen evolution at 10 mA cm−2 and 281 mV for oxygen evolution at 50 mA cm−2. Furthermore, in 1.0 M KOH solution, the outstanding bifunctional electrode (CP-NCP-T || CP-NCP-T) exhibits efficient electrochemical water splitting activity (1.54 V@10 mA cm−2) and outperforms the comparable device Pt/C || IrO2 (1.62 V@10 mA cm−2).

Iron-induced lattice distortion generally boots the graphene-supported nickel phosphide nanoparticles catalysis for efficient overall water splitting

Rational design of high-efficient, low-cost and stable bifunctional electrocatalysts is necessary but challenging for water electrolysis. Transition metal phosphides (TMPs) with rich redox properties are considered to be the most promising substitutes for noble-metal materials but with aggregation and poor intrinsic electrical conductivity. Herein, we report an ultra-fast and controllable microwave strategy for synthesizing Fe-doped nickel phosphide on reduced graphene oxide (Fe-Ni12P5/rGO) as a highly active bifunctional electrocatalyst for both hydrogen and oxygen evolution reactions (HER and OER). It is noteworthy that Fe introduction can significantly cause the lattice distortion of Ni12P5 and lead to the increase of electrocatalytic active sites and modulation of the electronic structure of each catalytic center. Benefiting from the highly active Fe-Ni12P5 nanoparticles and two-dimensional graphene conductive network, the as-fabricated Fe-Ni12P5/rGO shows excellent electrocatalytic activity for HER and OER with good stability. In addition, an overall water splitting device with Fe-Ni12P5/rGO as both the cathode and anode electrocatalysts requires only an extremely low cell voltage of 1.57 V to reach 10 mA cm−2, which is attractive among the latest research. This work provides a facile and effective approach for the design of high-performance transition metal-based electrocatalysts.

CoSe2 nanocrystals embedded into carbon framework as efficient bifunctional catalyst for alkaline seawater splitting

Herein, CoSe 2 nanocrystals embedded into carbon framework grown on carbon cloth is developed to catalyze the overall seawater splitting. • CoSe 2 nanocrystals embedded into carbon framework is synthesized as bifunctional catalyst for overall seawater splitting. • The catalyst shows overpotentials of 245 and 134 mV for OER and HER to reach 10 mA cm –2 , respectively. • The catalyst can operate at 1.842 V with a current density of 500 mA cm -2 in a two-electrode electrolyzer and work for 50 h. Direct seawater splitting is more attractive and feasible in realizing hydrogen economy, but the key challenge lies in the development of efficient and stable bifunctional electrocatalysts toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, CoSe 2 nanocrystals embedded into carbon framework grown on carbon cloth are successfully designed, featuring cooperative effect of CoSe 2 and nitrogen-doped carbon framework, which endow the excellent performance toward overall seawater splitting. The catalyst requires overpotentials of 245 and 134 mV for OER and HER to reach 10 mA cm –2 , respectively. Meantime, this catalyst also maintains robust electrocatalytic activity during over 50 h. Further, in the two-electrode alkaline seawater splitting electrolyzer, the catalyst shows a working voltage of 1.842 V to deliver 500 mA cm –2 at 80 o C, suggesting promising applications in sustainable hydrogen production. Our work may shed light on developing advanced and cost-effective electrocatalysts toward seawater splitting.