Catalysts For Overall Water Splitting Research Articles

MOF-derived nitrogen-doped CoO@CoP arrays as bifunctional electrocatalysts for efficient overall water splitting

In order to keep up with the increasing demands of renewable energy technologies, it is urgent to develop highly efficient bifunctional electrocatalysts for overall water splitting, which could produce hydrogen and oxygen at the same time. Herein, we report a self-supported bead string-like nitrogen-doped CoO@CoP (N–CoO@CoP) arrays derived from MOF materials, serving as a bifunctional catalyst for overall water splitting. The unique 3D bead string-like arrays endow unimpeded electronic transport path, abundant bubble release channels and expose more active sites, which can easily achieve high current density in the electrocatalytic reaction process. The doped atom N coming from nitrogen-contained MOF can tune the electronic structure of CoP, which enhances the electrocatalytic performance further. The electrocatalysts display superb oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance with a small overpotential of 332 mV and 201 mV at the current density of 100 mA cm−2, respectively. Moreover, an alkaline electrolyzer employing the N–CoO@CoP as the cathode and anode exhibits a cell voltage of 1.79 V at the current density of 100 mA cm−2 as well as robust durability.

Enhanced cobalt-based catalysts through alloying ruthenium to cobalt lattice matrix as an efficient catalyst for overall water splitting

The development of high activity, long stability, and cost-efficient catalyst for overall water splitting is paramount for the scalable production of hydrogen. Herein, we report low ruthenium content ruthenium cobalt nanoalloys encapsulated in nitrogen-doped carbon layers synthesized via incipient-wetness impregnation-pyrolysis method (denoted as RuCo@NC-temp.). A series of characterizations reveal that trace amounts of ruthenium inserts into the cobalt lattice matrix that can form RuCo alloys. The optimized catalyst (RuCo@NC-750, 1.56 wt% Ru) shows superior catalytic performance for hydrogen evolution reaction in alkaline, acidic, and neutral media, as well as oxygen evolution reaction in alkaline media. The catalytic reaction displays an overpotential of 25 mV (1.0 M KOH), 29 mV (0.5 M H2SO4), and 163 mV (1.0 M PBS) for hydrogen evolution reaction and 308 mV (1.0 M KOH) for oxygen evolution reaction at a current density of 10 mA cm−2. RuCo@NC-750 needs only 1.54 V to achieve a current density of 10 mA cm−2 when it serves as both the anode and cathode material in a two-electrode electrolyzer. The excellent electrocatalytic performance can be attributed to the doping of ruthenium into the cobalt lattice matrix, which effectively enhance the electron transfer from the metal core to the carbon surface, and is beneficial for regulating the electronic structure of the carbon surface and strengthening the carbon-hydrogen bond and surface defects.

Laser Synthesis of Iridium Nanospheres for Overall Water Splitting.

Engineering surface structure of catalysts is an efficient way towards high catalytic performance. Here, we report on the synthesis of regular iridium nanospheres (Ir NSs), with abundant atomic steps prepared by a laser ablation technique. Atomic steps, consisting of one-atom level covering the surface of such Ir NSs, were observed by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The prepared Ir NSs exhibited remarkably enhanced activity both for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in acidic medium. As a bifunctional catalyst for overall water splitting, they achieved a cell voltage of 1.535 V @ 10 mA/cm2, which is much lower than that of Pt/C-Ir/C couple (1.630 V @ 10 mA/cm2).

Coupling NiSe2-Ni2P heterostructure nanowrinkles for highly efficient overall water splitting

Developing catalysts with high efficiency and low-cost toward overall water splitting is critical for the sustainable energy conversion. Herein, a facile wet-chemical route followed by successive selenization and partial phosphorization treatments is presented to synthesize the heterostructure combining NiSe2 and Ni2P coupled nanowrinkles on Ni foam (NiSe2-Ni2P/NF). DFT calculation results confirm that the NiSe2 coupled with Ni2P in NiSe2-Ni2P/NF can promote the water adsorption process, speeding up the whole catalytic kinetics for overall water splitting. Benefitting from the synergistic effects between NiSe2 and Ni2P, the optimal NiSe2-Ni2P/NF electrode exhibits excellent catalytic performances toward both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media. Impressively, for OER such heterogeneous nanowrinkles merely require an ultralow overpotential of 220 mV to reach the current density of 50 mA cm−2. Moreover, when utilized as a bifunctional catalyst for overall water splitting, the current density of 10 mA cm−2 can be delivered at an ultralow cell voltage of 1.50 V, which is among the lowest values of current non-precious metal catalysts. This work provides a unique strategy for exploring highly efficient heterostructure catalysts toward water splitting and beyond.

Fe2+ -Doped Layered Double (Ni, Fe) Hydroxides as Efficient Electrocatalysts for Water Splitting and Self-Powered Electrochemical Systems.

Developing nonprecious electrocatalysts with superior activity and durability for electrochemical water splitting is of great interest but challenging due to the large overpotential required above the thermodynamic standard potential of water splitting (1.23 V). Here, in situ growth of Fe2+ -doped layered double (Ni, Fe) hydroxide (NiFe(II,III)-LDH) on nickel foam with well-defined hexagonal morphology and high crystallinity by a redox reaction between Fe3+ and nickel foam under hydrothermal conditions is reported. Benefiting from tuning the local atomic structure by self-doping Fe2+ , the NiFe(II,III)-LDH catalyst with higher amounts of Fe2+ exhibits high activity toward oxygen evolution reaction (OER) as well as hydrogen evolution reaction (HER) activity. Moreover, the optimized NiFe(II,III)-LDH catalyst for OER (O-NiFe(II,III)-LDH) and catalyst for HER (H-NiFe(II,III)-LDH) show overpotentials of 140 and 113 mV, respectively, at a current density of 10 mA cm-2 in 1 m KOH aqueous electrolyte. Using the catalysts for overall water splitting in two-electrode configuration, a low overpotential of just 1.54 V is required at a benchmark current density of 10 mA cm-2 . Furthermore, it is demonstrated that electrolysis of the water device can be drived by a self-powered system through integrating a triboelectric nanogenerator and battery, showing a promising way to realize self-powered electrochemical systems.

Self-supported hollow Co(OH)2/NiCo sulfide hybrid nanotube arrays as efficient electrocatalysts for overall water splitting

Developing low-cost and earth-abundant electrocatalysts with high activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is highly desired but still remains a significant challenge. Herein, hollow cobalt hydroxide/NiCo sulfide hybrid (Co(OH)2/Ni-Co-S) nanotube arrays are synthesized on nickel foam (NF) through a simple hydrothermal method and subsequent sulfurization, which serve as efficient electrocatalysts for overall water splitting. The optimized Co(OH)2/Ni-Co-S-8h electrocatalyst requires overpotentials of 300 mV and 340 mV to reach current densities of 30 and 100 mA cm−2 for the OER in 1.0 M KOH, respectively. In addition, the optimized Co(OH)2/Ni-Co-S-8h electrocatalyst requires overpotentials of 148 mV and 254 mV to reach the current densities of 10 and 100 mA cm−2 for the HER in the same electrolyte, respectively. Furthermore, the electrolyzer used as efficient catalysts for overall water splitting requires cell voltage of 1.62 V to obtain 10 mA cm−2.

Ultrathin carbon coated mesoporous Ni-NiFe2O4 nanosheet arrays for efficient overall water splitting

Developing low-cost, highly efficient electrocatalysts for water splitting is a crucial and challengeable task to produce clean hydrogen fuel. Here, for the first time, we reported a novel ultrathin carbon layer coated mesoporous Ni-NiFe2O4 (Ni-NiFe2O4@C) nanosheet arrays catalyst by hydrothermal growth of NiFe-precursor on carbon cloth followed by a thermal decomposition process. The resultant Ni-NiFe2O4@C catalyst displays excellent electrocatalytic performances toward both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline electrolyte, which requires overpotential of 212 mV for OER and 217 mV for HER to reach 10 mA cm−2 with Tafel slope of 51 and 96 mV dec−1, respectively. Moreover, the two-electrode electrolyzer made of Ni-NiFe2O4@C electrodes requires a cell voltage of 1.57 V to deliver a current density of 10 mA cm−2 with long-term stability, which is superior to that of RuO2//Pt/C electrolyzer. This work offers new insight into the design and development of transition metal-based oxides catalysts for overall water splitting.

Ultrathin amorphous CoFeP nanosheets derived from CoFe LDHs by partial phosphating as excellent bifunctional catalysts for overall water splitting

Non-noble-metal electrocatalysts of transition metal phosphides have been considered as promising catalysts for hydrogen evolution reaction (HER); however, their bifunctional catalytic activities are limited by unsatisfactory performance in oxygen evolution reaction (OER). Here we report ultrathin amorphous CoFeP nanosheets derived from CoFe layered double hydroxides (LDHs) as bifunctional electrocatalysts with a simple phosphorization method. The partial phosphating induced by sodium hypophosphite can greatly reduce the thickness of nanosheets and promote the polycrystalline nature of the materials, leading to more active sites exposed and faster electronic transport. The optimal levels of phosphating agents are 1.8 g for OER and 2.4 g for HER, respectively, etched by which the resultant CoFeP materials can exhibit excellent electrocatalytic performances toward OER, HER and overall water splitting in alkaline media. At the current densities of 100 and 20 mA cm−2, ultralow overpotentials of 242 and 80 mV are achieved for OER and HER, individually, which are 128 mV lower than RuO2 and 6 mV slightly lower than Pt, respectively. In a cell voltage of 1.62 V, the CoFeP materials reacted with 1.8 and 2.4 g phosphating agents and used as the anode and the cathode, respectively, can achieve 100 mA cm−2 current density and exhibit extraordinary durability for 30 h in overall water splitting. These superior electrocatalytic properties of ultrathin amorphous CoFeP nanosheets are comparable to those of state-of-the-art noble metal and other reported catalysts for OER, HER and overall water splitting. This work proposes a promising strategy for excellent bifunctional electrocatalysts by tailoring the morphology and crystallinity degree based on LDHs through a facile partial phosphating method.

Controllable synthesis of Mo[sbnd]O linkage enhanced CoP ultrathin nanosheet arrays for efficient overall water splitting

Developing cost-effective and high-performance bifunctional catalysts for overall water splitting is of enormous importance for the realization of sustainable clean-energy technologies. Herein, the unique MoO linkage enhanced CoP nanosheets supported on Ni foam (NF) and the systematical investigation of their performance for overall water splitting as a function of the composition are reported. The fine-tuning of Co/Mo ratios in the CoMo precursors realized by controlling the dosages of capping agent (urea), which enables CoO to grow along its (111) crystalline orientation and retard the incorporation of MoO. As a result, the optimized CoP/MOL/NF-10 exhibits the best hydrogen evolution reaction (HER) activity with low overpotentials (η) of 87 mV at 10 mA cm−2. DFT calculation confirmed the O-site on surface is more advantageous to the adsorption of H, when CoP with proper mounts of MoO linkages and giving rise to a decent ΔGH value. When the CoP/MOL/NF-10 employed as anode for OER, the current density of 20 mA cm−2 is achieved at a low overpotential of 270 mV. In the end, a symmetric electrolyzer built by CoP/MOL/NF-10 deliveries a current density of 10 mA cm−2 at a cell voltage of 1.52 V with excellent stability.

Scalable Synthesis of Bimetallic Phosphide Decorated in Carbon Nanotube Network as Multifunctional Electrocatalyst for Water Splitting

It is challengeable to obtain a scalable method to synthesize nonprecious electrocatalysts with high efficiency and stability for overall water splitting, to replace the costly and scarce noble metal based electrocatalysts (e.g., Pt- and Ru-based materials). Herein, bimetallic (Fe, Co)P nanoparticles decorated in carbon nanotube network (FCP-CN) are synthesized through a facile and scalable spray drying and subsequent phosphorization process. The FCP-CN hybrid delivers excellent performance in hydrogen evolution reaction both in acidic and alkaline media, oxygen evolution reaction, and overall water splitting: it possesses an Pt-like hydrogen evolution reaction activity with an ultralow onset overpotential of 18 mV in acid; remarkably, it shows an ultrasmall Tafel slope of 38 mV dec–1 in oxygen evolution reaction; being employed as both cathode and anode, this catalyst demonstrates promising performance of overall water splitting with high long-term stability. The performance is superior among recently reported transition-metal-based catalysts for overall water splitting. This work provides a scalable and low-cost synthesis strategy to synthesize nonprecious and multifunctional transition-metal-based catalysts with unique nanoarchitecture and outstanding catalytic performance for water splitting.

Porous Nitrogen Self‐Doped Carbon Wrapped Iron Phosphide Hollow Spheres as Efficient Bifunctional Electrocatalysts for Water Splitting

AbstractIn this work, a series of hybrid materials of N‐self‐doped carbon wrapped Fe2P/FeP hollow spheres were prepared by using a two‐step thermal conversion of precursors derived from the in situ coating of polyaniline on commercial Prussian blue. The precursors were pyrolyzed in N2 to form the N‐doped carbon coating on carbon‐iron materials; this was followed by subsequent phosphorization using NaH2PO2 as a phosphorus source, yielding the hybrid materials of N‐doped carbon wrapped Fe2P/FeP hollow spheres. The resulting hybrid materials showed high Brunauer‐Emmett‐Teller surface areas, pore volumes, and nitrogen contents, which were, more than 80 % pyridinic‐N. The hybrid materials were evaluated as electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH, and they have exhibited excellent electrocatalytic activities in the two reactions. In the case of the optimum sample, the 0.75‐NC−FexP catalyst, a low overpotential/Tafel slope of 193 mV/58 mV ⋅ dec−1 for HER and 302 mV/42 mV ⋅ dec−1 for OER were obtained. More importantly, the catalyst showed high catalytic activity for overall water splitting and only 1.63 V of cell voltage was needed to reach 10 mA/cm2 in a two‐electrode electrolyzer. The catalyst also exhibited robust long‐term durability and only a 16.0 % decrease in current density was observed after a 10 h chronoamperometric testing at 1.63 V. The results suggest that the sample is a promising alternative non‐precious‐metal catalyst for overall water splitting.

Bimetallic transition metal chalcogenide nanowire array: An effective catalyst for overall water splitting

The development of highly active, durable, and inexpensive bifunctional catalysts towards both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is one of the most challenging tasks in the term of renewable energy. Keeping in mind the current scenario, herein, we have synthesized bimetallic transition metal chalcogenides (CoTe2@CdTe and CoSe2@CdSe) by a very easy, single step hydrothermal process. During the synthesis, two different morphologies (i.e. spherical and wire) were obtained depending on the selection of chalcogen. It was found that Te based nanocomposite i.e. CoTe2@CdTe showed a symmetrical nanowire array morphology with a high electrocatalytic surface area and good electrocatalytic activity towards both HER and OER. The structural, morphological and electrochemical features of synthesized nanocomposites were characterized by various useful techniques (like field emission scanning electron microscopy, high resolution transmission electron microscopy, powder X-ray diffraction analysis etc.) to confirm their successful synthesis. The CoTe2@CdTe nanowire array has shown a small onset potential value, high current density, low Tafel slope value along with high stability towards overall water splitting.

Core-shell copper oxide @ nickel/nickel–iron hydroxides nanoarrays enabled efficient bifunctional electrode for overall water splitting

The design of efficient and low-cost electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) remains a significant challenge for the hydrogen production. Herein, CuO nanowires encapsulated by Ni and NiFe hydroxides (CuO@Ni/NiFe hydroxides) in-situ grown on the surface of Cu plate were fabricated via chemical oxidation-calcination process and room-temperature interfacial Galvanic reaction, which were applied to the efficient overall water splitting. Thanks to the improved specific surface area and the conductivity, the optimized core-shell CuO@Ni/NiFe hydroxides nanowire array exhibit impressive OER performance as well as HER activity in 1 M KOH which delivers a current density of 10 mA cm−2 at an overpotential of 230 mV for OER and 125 mV for HER. Significantly, core-shell CuO@Ni/NiFe hydroxides used as bifunctional catalysts for an overall water splitting can achieve a low onset potential of ∼1.50 V and a relatively high specific current density of 40 mA cm−2 at ∼1.73 V. This feasible strategy provides an accumulative opportunity for fabricating low-cost, effective bifunctional catalysts for overall water splitting.

High-efficiency bifunctional electrocatalyst based on 3D freestanding Cu foam in situ armored CoNi alloy nanosheet arrays for overall water splitting

It is highly desired to design and develop highly efficient and durable electrocatalysts for hydrogen evolution reaction and oxygen evolution reaction under alkaline condition. In this study, three dimensional freestanding porous Cu foam in situ armored CoNi alloy nanosheet arrays with tunable compositions is synthesized via a facile and cost-efficient electrodeposition strategy. With the optimal nanosheet composition (Co81Ni19), highly exposed active surface, improved electrical conductivity, the as-fabricated composite exhibits intriguing properties for efficient overall water splitting in alkaline media. Such freestanding Co81Ni19 alloy nanosheet arrays demonstrate superior electrocatalytic performances with the overpotentials of only 132 and 240 mV for hydrogen evolution and oxygen evolution to reach a catalytic current density of 10 mA cm−2 in 1.0 M KOH. Meanwhile, the Co81Ni19 exhibits high electrochemical stability with almost no detectable activity decay after 36,000 s of continuous operation. Remarkably, this study paves the way to design high-performance and easy-accessible transition metal alloy-based bifunctional catalysts for overall water splitting. Meanwhile, these transition metal-based macroscopic assemblies may be attractive candidates for a wide range of practical energy conversion and storage applications.

Zirconium-Regulation-Induced Bifunctionality in 3D Cobalt-Iron Oxide Nanosheets for Overall Water Splitting.

The design of high-efficiency non-noble bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is paramount for water splitting technologies and associated renewable energy systems. Spinel-structured oxides with rich redox properties can serve as alternative low-cost OER electrocatalysts but with poor HER performance. Here, zirconium regulation in 3D CoFe2 O4 (CoFeZr oxides) nanosheets on nickel foam, as a novel strategy inducing bifunctionality toward OER and HER for overall water splitting, is reported. It is found that the incorporation of Zr into CoFe2 O4 can tune the nanosheet morphology and electronic structure around the Co and Fe sites for optimizing adsorption energies, thus effectively enhancing the intrinsic activity of active sites. The as-synthesized 3D CoFeZr oxide nanosheet exhibits high OER activity with small overpotential, low Tafel slope, and good stability. Moreover, it shows unprecedented HER activity with a small overpotential of 104 mV at 10 mA cm-2 in alkaline media, which is better than ever reported counterparts. When employing the CoFeZr oxides nanosheets as both anode and cathode catalysts for overall water splitting, a current density of 10 mA cm-2 is achieved at the cell voltage of 1.63 V in 1.0 m KOH.

MoS2 nanosheets decorated Ni(OH)2 nanorod array for active overall water splitting

Integrating heterogeneous hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts into compatible composite catalysts with specific interfaces and structures holds great promise for the development of efficient bifunctional catalysts for overall water splitting. Herein, heterogeneous MoS2-Ni(OH)2 catalyst supported by Ni foam (MoS2@Ni(OH)2/NF) is developed, in which the Ni(OH)2 nanorod array is grafted with MoS2 nanosheets. The hierarchical 1D/2D structures benefit not only the exposure of catalytic site but also the facilitated charge transfer. The heterointerfaces allow the synergism of electric structure modulation for improved catalytic activity and kinetics towards HER, OER, and overall water splitting. MoS2@Ni(OH)2/NF achieves a current density of 10 mA cm−2 at low overpotentials of 134 and 233 mV for HER and OER in 1 M KOH, respectively. Moreover, a cell voltage as low as 1.46 V is obtained to afford 10 mA cm−2 in a tow-electrode electrolyzer using MoS2@Ni(OH)2/NF as bifunctional catalysts, assuring it superior to most of the reported noble-metal-free bifunctional electrocatalysts. Such heterogeneous design of composite catalyst should shed light on the exploration of functional materials for energy applications.

A novel strategy for 2D/2D NiS/graphene heterostructures as efficient bifunctional electrocatalysts for overall water splitting

Designing non-precious-metal bifunctional electrocatalysts with highly efficient overall water splitting in basic media still remain a signification challenge. In this work, an environment-friendly and one-step strategy is developed to synthesize two-dimensional (2D/2D) NiS/graphene heterostructure composites via a pyrolysis accompanied sulfidation process using novel deep eutectic solvents (DESs) as precursors. The as-obtained 2D NiS/graphene heterostructures manifest excellent HER and OER activity in alkaline solution. Furthermore, the optimized 2D/2D heterostructure as a bifunctional catalyst for overall water splitting exhibits a low cell voltage of 1.54 V at 10 mA cm−2 in alkaline media, even superior than that of the integrated Pt/C and IrO2 couples. The one-step DESs based procedure favors the interface coupling between graphene and NiS nanosheets, which significantly brings high surface-active sites exposure, enhances electrical conductivity, and results in high electrocatalytic activity. The DESs precursor has the advantage of solution reaction and acts as an environment-friendly synthetic strategy for clean energy generation.

Rational Design of Manganese Cobalt Phosphide with Yolk–Shell Structure for Overall Water Splitting

The development of low‐cost, earth‐abundant, and efficient catalysts for overall water splitting, involving the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), attracts tremendous attention in recent years. Herein, this work reports the preparation of Mn‐Co phosphide (Mn‐Co‐P) bifunctional catalysts with a yolk–shell structure by a facile hydrothermal route. The as‐prepared catalysts exhibit an excellent catalytic activity with the low overpotentials of 66 mV at 10 mA cm−2 for HER and 355 mV at 50 mA cm−2 for OER in 1 m KOH, along with an outstanding stability. More importantly, the cell voltage of 1.74 V can achieve a current density of 10 mA cm−2 when assembled as an electrolyzer for overall water splitting. Such superior performance makes the Mn‐Co‐P a promising candidate to replace Pt‐based noble metal catalysts for electrocatalytic applications.

(Invited) Role of Surface States in Photocatalytic Oxygen Evolution with CuWO4 Particles

CuWO4 is a medium bandgap (2.3 eV) n-type semiconductor capable of photoelectrochemical water oxidation under applied electrical bias. Here, we show for the first time that suspended microcrystals CuWO4 evolve oxygen photocatalytically under visible illumination from solutions of 0.05 M AgNO3(10.8 μmol/hour; AQE of 0.561% at 400 nm) and 0.0002 M FeCl3(1.5 μmol/hour). No oxygen is detected with 0.002 M [Fe(CN)6]3-as sacrificial agent. The activity dependence on the redox potential of the acceptors is due to the presence of Cu2+based electron trap states in CuWO4. According to surface photovoltage spectroscopy and electrochemistry, these states are located on the particle surface, 1.8 eV above the valence band edge of the material. Controlling the chemistry of these states will be key to uses of CuWO4particles in tandem catalysts for overall water splitting. Figure 1

Synergistic Effects of Mo2C‐NC@CoxFey Core–Shell Nanoparticles in Electrocatalytic Overall Water Splitting Reaction

Transition metals (TMs) are highly investigated as nonprecious electrocatalysts for hydrogen evolution (HER) and oxygen evolution (OER) reactions. There is a strong demand for highly efficient and inexpensive catalysts for overall water splitting. Herein, the bimetallic CoxFey alloy nanoparticles encapsulated in a N‐doped graphene shell containing molybdenum carbide (Mo2C) nanoparticles are synthesized by the pyrolysis of cobalt ferrite (CoxFe3−xO4) nanoparticles coated by melamine‐formaldehyde resin cross‐linked with molybdic acid. Molybdic acid not only serves as precursor for the formation of highly dispersed Mo2C nanoparticles in the N‐doped graphene shell but also enhances the thermal stability of the organic shell, resulting in the formation of smaller CoxFey cores. The formation of Mo2C nanoparticles in the graphene shell is promoted by the CoxFe3−xO4 core. Interestingly, the synergistic presence of Mo2C nanoparticles not only enhances the HER activity of the material but also renders a partial breakage of the graphene shell, which increases the surface concentration of OER‐active Co and therefore enhances the OER activity. The as‐prepared TM‐based materials serve as bifunctional catalysts for the overall water splitting and exhibit improved electrocatalytic performances compared to standard cells based on precious metals, with the potentials of 1.53 and 1.60 V at 10 and 20 mA cm−2 in alkaline media, respectively.