Heterogeneous Bimetallic Mo-NiPx/NiSy as a Highly Efficient Electrocatalyst for Robust Overall Water Splitting

Highly efficient electrocatalysts composed of earth-abundant elements are desired for water-splitting to produce clean and renewable chemical fuel. Herein, a heteroatomic-doped multi-phase Mo-doped nickel phosphide/nickel sulfide (Mo-NiP_x/NiS_y) nanowire electrocatalyst is designed by a successive phosphorization and sulfuration method for boosting overall water splitting (both oxygen and hydrogen evolution reactions (HER)) in alkaline solution. As expected, the Mo-NiP_x/NiS_y electrode possesses low overpotentials both at low and high current densities in HER, while the Mo-NiP_x/NiS_y heterostructure exhibits high active performance with ultra-low overpotentials of 137, 182, and 250 mV at the current density of 10, 100, and 400 mA cm⁻² in 1 m KOH solution, respectively, in oxygen evolution reaction. In particular, the as-prepared Mo-NiP_x/NiS_y electrodes exhibit remarkable full water splitting performance at both low and high current densities of 10, 100, and 400 mA cm⁻² with 1.42, 1.70, and 2.36 V, respectively, which is comparable to commercial electrolysis.     

Porous Pd/NiFeOx Nanosheets Enhance the pH-Universal Overall Water Splitting

Modulating the morphology and chemical composition is an efficient strategy to enhance the catalytic activity for water splitting, since it is still a great challenge to develop a bifunctional catalyst for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) over a wide pH range. Herein, Pd/NiFeO_x nanosheets are synthesized with tightly arranged petal nanosheets and uniform mesoporous structure on nickel foam (NF). The porous 2D structure yields a larger surface area and exposes more active sites, facilitating water splitting at all pH values. The overpotential of Pd/NiFeO_x nanosheets for OER is only 180, 169, and 310 mV in 1 m KOH, 0.5 m H₂SO₄, and 1 m phosphate-buffered saline (PBS) conditions at 10 mA cm⁻² current density, as well as excellent HER activity with ultralow overpotential in a wide pH range. When using porous Pd/NiFeO_x nanosheets as bifunctional catalysts for water splitting, it just required a cell voltage of 1.57 V to reach a current density of 20 mA cm⁻² with nearly 100% faradic efficiency in alkaline conditions, which is much lower than that of benchmark Pt/CǁRuO₂ (1.76 V) couples, along with the improving stability benefiting from the good corrosion resistance of the inner NiFeO_x nanosheets.     

Rapid Synthesis of Various Electrocatalysts on Ni Foam Using a Universal and Facile Induction Heating Method for Efficient Water Splitting

Electrocatalytic water splitting for the production of hydrogen proves to be effective and available. In general, the thermal radiation synthesis usually involves a slow heating and cooling process. Here, a high-frequency induction heating (IH) is employed to rapidly prepare various self-supported electrocatalysts grown on Ni foam (NF) in liquid- and gas-phase within 1–3 min. The NF not only serves as an in situ heating medium, but also as a growth substrate. The as-synthesized Ni nanoparticles anchored on MoO₂ nanowires supported on NF (Ni-MoO₂/NF-IH) enable catalysis of hydrogen evolution reaction (HER), showing a low overpotential of −39 mV (10 mA cm⁻²) and maintaining the stability of 12 h in alkaline condition. Moreover, the NiFe layered double hydroxide (NiFe LDH/NF-IH) is also synthesized via IH and affords outstanding oxygen evolution reaction (OER) activity with an overpotential of 246 mV (10 mA cm⁻²). The Ni-MoO₂/NF-IH and NiFe LDH/NF-IH are assembled to construct a two-electrode system, where a small cell voltage of ≈1.50 V enables a current density of 10 mA cm⁻². More importantly, this IH method is also available to rapidly synthesize other freestanding electrocatalysts on NF, such as transition metal hydroxides and metal nitrides.     

Mo-/Co-N-C Hybrid Nanosheets Oriented on Hierarchical Nanoporous Cu as Versatile Electrocatalysts for Efficient Water Splitting

Designing robust and cost-effective electrocatalysts based on Earth-abundant elements is crucial for large-scale hydrogen production through electrochemical water splitting. Here, nitrogen-doped carbon engrafted Mo₂N/CoN hybrid nanosheets that are seamlessly oriented on hierarchical nanoporous Cu scaffold (Mo-/Co-N-C/Cu), as highly efficient electrocatalysts for alkaline hydrogen evolution reaction are reported. The constituent heterostructured Mo₂N/CoN nanosheets work as bifunctional electroactive sites for both water dissociation and adsorption/desorption of hydrogen intermediates while the nitrogen-doped carbon bridges electron transfers between electroactive sites and interconnective Cu current collectors by making use of Mo-/Co-N-C bonds and intimate C/Cu contacts at interfaces. As a consequence of unique architecture having electroactive sites to be sufficiently accessible, self-supported nanoporous Mo-/Co-N-C/Cu hybrid electrodes exhibit outstanding electrocatalysis in 1 m KOH, with a negligible onset overpotential and a low Tafel slope of 47 mV dec⁻¹. They only take overpotential of as low as 230 mV to reach current density of 1000 mA cm⁻². When coupled with their electro-oxidized derivatives that mediate efficiently the oxygen evolution reaction, the alkaline water electrolyzer can achieve ≈100 mA cm⁻² at 1.622 V in 1 m KOH electrolyte, ≈0.343 V lower than the device constructed with commercially available Pt/C and Ir/C nanocatalysts immobilized on nanoporous Cu electrodes.     

Realizing the Synergy of Interface Engineering and Chemical Substitution for Ni3N Enables its Bifunctionality Toward Hydrazine Oxidation Assisted Energy-Saving Hydrogen Production

Hydrazine oxidation assisted water electrolysis offers a unique rationale for energy-saving hydrogen production, yet the lack of effective non-noble-metal bifunctional catalysts is still a grand challenge at the current stage. Here, the Mo doped Ni₃N and Ni heterostructure porous nanosheets grow on Ni foam (denoted as Mo Ni₃N/Ni/NF) are successfully constructed, featuring simultaneous interface engineering and chemical substitution, which endow the outstanding bifunctional electrocatalytic performances toward both hydrazine oxidation reaction (HzOR) and hydrogen evolution reaction (HER), demanding a working potential of −0.3 mV to reach 10 mA cm⁻² for HzOR and −45 mV for that of HER. Impressively, the overall hydrazine splitting (OHzS) system requires an ultralow cell voltage of 55 mV to deliver 10 mA cm⁻² with remarkable long-term durability. Moreover, as a proof-of-concept, economical H₂ production systems utilizing OHzS unit powered by a waste AAA battery, a commercial solar cell, and a homemade direct hydrazine fuel cell (DHzFC) are investigated to inspire future practical applications. The density functional theory calculations demonstrate that the synergy of Mo substitution and abundant Ni₃N/Ni interface owns a more thermoneutral value for H* absorption ability toward HER and optimized dehydrogenation process for HzOR.     

Hierarchical Crystalline/Amorphous Heterostructure MoNi/NiMoOx for Electrochemical Hydrogen Evolution with Industry-Level Activity and Stability

The design of cheap, efficient, and durable electrocatalysts for high-throughput H₂ production is critical to give impetus to hydrogen production from fundamental to practical industrial applications. Here, a hierarchical heterostructure hydrogen evolution reaction (HER) electrocatalyst (MoNi/NiMoO_x) with 0D MoNi nanoalloys nanoparticles embedded on well-assembled 1D porous NiMoO_x microrods in situ grown on 3D nickel foam (NF) is successfully constructed. The synergetic effect of different building units in the unique hierarchical structure endows the MoNi/NiMoO_x composites with the highly active heterogeneous interface with low water dissociation energy (ΔG_diss = −1.2 eV) and optimized hydrogen adsorption ability (ΔG_H* = −0.01 eV), fast electron/mass transport, and strong catalyst-support binding force. As a result, optimal MoNi/NiMoO_x exhibits an ampere-level current density of 1.9 A cm⁻² at an ultralow overpotential of 139 mV in 1.0 м KOH and 289 mV in 1.0 м PBS solution, respectively. Particularly, scaled-up MoNi/NiMoO_x electrodes in a 10 × 10 cm² membrane electrode assembly (MEA) electrolyzer reach a high H₂ production rate of 12.12 L h⁻¹ (12.12 times than that of commercial NF) and exhibit ultralong stability of 1600 h, verifying its huge potential for industrial hydrogen production.     

A Novel Photocathode Material for Sunlight‐Driven Overall Water Splitting: Solid Solution of ZnSe and Cu(In,Ga)Se2

Thin films of a solid solution of ZnSe and CuIn_0.7Ga_0.3Se₂ ((ZnSe) _x (CIGS) _1–x ) are prepared by co‐evaporation. Structural characterization reveals that the ZnSe and CIGS form a solid solution with no phase separation. (ZnSe)_0.85(CIGS)_0.15‐based photocathodes modified with Pt, Mo, Ti, and CdS exhibit a photocurrent of 7.1 mA cm^?2 at 0 V_RHE, and a relatively high onset potential of 0.89 V_RHE under simulated sunlight. A two‐electrode cell containing a (ZnSe)_0.85(CIGS)_0.15 photocathode and a BiVO₄‐based photoanode has an initial solar‐to‐hydrogen conversion efficiency of 0.91%, which is one of the highest values reported for a photoanode–photocathode combination. Thus, (ZnSe)_0.85(CIGS)_0.15 is a promising photocathode material for efficient photoelectrochemical water splitting.     

Fabrication of Polyoxometalate Anchored Zinc Cobalt Sulfide Nanowires as a Remarkable Bifunctional Electrocatalyst for Overall Water Splitting

The advancement of a naturally rich and effective bifunctional substance for hydrogen and oxygen evolution reaction is crucial to enhance hydrogen fuel production efficiency via the electrolysis process. Herein, facile and scalable hydrothermal synthesis of bifunctional electrocatalyst of polyoxometalate anchored zinc cobalt sulfide nanowire on Ni-foam (NF) for overall water splitting is reported for the first time. The electrochemical analysis of POM@ZnCoS/NF displays significantly low HER and OER overpotentials of 170/337 and 200/300 mV to attain a current density of 10/40 and 20/50 mA cm⁻², respectively, demonstrating the notable performance of POM@ZnCoS/NF toward H₂ and O₂ evolution reaction in alkaline medium. Additionally, the electrolyzer consisting of the POM@ZnCoS/NF anode and cathode shows an appealing potential of 1.56 V to deliver 10 mA cm⁻² current density for overall water splitting. The high electrocatalytic activity of the POM@ZnCoS/NF is attributed to modulation of the electronic and chemical properties, increment of the electroactive sites and electrochemically active surface area of the zinc cobalt sulfide nanowires due to the anchorage of polyoxometalate nanoparticles. These results demonstrate the advantage of the polyoxometalate incorporation strategy for the design of cost-effective and highly competent bifunctional catalysts for complete water splitting.     

Rational Engineering CoxOy Nanosheets via Phosphorous and Sulfur Dual-Coupling for Enhancing Water Splitting and Zn–Air Battery

Herein, an efficient multifunctional catalyst based on phosphorus and sulfur dual-doped cobalt oxide nanosheets supported by Cu@CuS nanowires is developed for water splitting and Zn–air batteries. The formation of such a unique heterostructure not only enhances the number and type of electroactive sites, but also leads to modulated electronic structure, which produces reasonable adsorption energy toward the reactant, thereby improving electrocatalytic efficiency. The catalyst demonstrates small overpotentials of 116 and 280 mA cm⁻² to achieve 10 mA cm⁻² for hydrogen and oxygen evolution, respectively. As a result, a developed electrolyzer displays a cell voltage of 1.52 V at 10 mA cm⁻² and long-term stability with a current response of 92.3% after operating for 30 h. Moreover, using such a catalyst in the fabrication of a Zn–air battery also leads to a cell voltage of 1.383 V, along with a power density of 130 mW cm⁻² at 220 mA cm⁻².     

Dense Platinum/Nickel Oxide Heterointerfaces with Abundant Oxygen Vacancies Enable Ampere-Level Current Density Ultrastable Hydrogen Evolution in Alkaline

Platinum (Pt) remains the benchmark electrocatalyst for alkaline hydrogen evolution reaction (HER), but its industry-scale hydrogen production is severely hampered by the lack of well-designed durable Pt-based materials that can operate at ampere-level current densities. Herein, based on the original oxide layer and parallel convex structure on the surface of nickel foam (NF), a 3D quasi-parallel architecture consisting of dense Pt nanoparticles (NPs) immobilized oxygen vacancy-rich NiO_x heterojunctions (Pt/NiO_x-O_V) as an alkaline HER catalyst is developed. A combined experimental and theoretical studies manifest that anchoring Pt NPs on NiO_x-O_V leads to electron-rich Pt species with altered density of states (DOS) distribution, which can efficiently optimize the d-band center and the adsorption of reaction intermediates as well as enhance the water dissociation ability. The as-prepared catalyst exhibits extraordinary HER performance with a low overpotential of 19.4 mV at 10 mA cm⁻², a mass activity 16.3-fold higher than that of 20% Pt/C, and a long durability of more than 100 h at 1000 mA cm⁻². Furthermore, the assembled alkaline electrolyzer combined with NiFe-layered double hydroxide requires extremely low voltage of 1.776 V to attain 1000 mA cm⁻², and can operate stably for more than 400 h, which is rarely achieved.     

Active Site Implantation for Ni(OH)2 Nanowire Network Achieves Superior Hybrid Seawater Electrolysis at 1 A cm−2 with Record-Low Cell Voltage

Direct seawater electrolysis provides a grand blueprint for green hydrogen (H₂) technology, while the high energy consumption has severely hindered its industrialization. Herein, a promising active site implantation strategy is reported for Ni(OH)₂ nanowire network electrode on nickel foam substrate by Ru doping (denoted as Ru Ni(OH)₂ NW²/NF), which can act as a dual-function catalyst for hydrazine oxidation and hydrogen evolution, achieving an ultralow working potential of 114.6 mV to reach 1000 mA cm⁻² and a small overpotential of 30 mV at 10 mA cm⁻², respectively. Importantly, using the two-electrode hydrazine oxidation assisted seawater electrolysis, it can drive a large current density of 500 mA cm⁻² at 0.736 V with over 200 h stability. To demonstrate the practicability, a home-made flow electrolyzer is constructed, which can realize the industry-level rate of 1 A cm⁻² with a record-low voltage of 1.051 V. Theoretical calculations reveal that the Ru doping activates Ni(OH)₂ by upgrading d-band centers, which raises anti-bonding energy states and thus strengthens the interaction between adsorbates and catalysts. This study not only provides a novel rationale for catalyst design, but also proposes a feasible strategy for direct alkaline seawater splitting toward sustainable, yet energy-saving H₂ production.     

Autogenous Growth of Hierarchical NiFe(OH)x/FeS Nanosheet‐On‐Microsheet Arrays for Synergistically Enhanced High‐Output Water Oxidation

Practical electrochemical water splitting requires cost‐effective electrodes capable of steadily working at high output, leading to the challenges for efficient and stable electrodes for the oxygen evolution reaction (OER). Herein, by simply using conductive FeS microsheet arrays vertically pre‐grown on iron foam (FeS/IF) as both substrate and source to in situ form vertically aligned NiFe(OH)_x nanosheets arrays, a hierarchical electrode with a nano/micro sheet‐on‐sheet structure (NiFe(OH)_x/FeS/IF) can be readily achieved to meet the requirements. Such hierarchical electrode architecture with a superhydrophilic surface also allows for prompt gas release even at high output. As a result, NiFe(OH)_x/FeS/IF exhibits superior OER activity with an overpotential of 245 mV at 50 mA cm^?2 and can steadily output 1000 mA cm^?2 at a low overpotential of 332 mV. The water‐alkali electrolyzer using NiFe(OH)_x/FeS/IF as the anode can deliver 10 mA cm^?2 at 1.50 V and steadily operate at 300 mA cm^?2 with a small cell voltage for 70 h. Furthermore, a solar‐driven electrolyzer using the developed electrode demonstrates an exceptionally high solar‐to‐hydrogen efficiency of 18.6%. Such performance together with low‐cost Fe‐based materials and facile mass production suggest the present strategy may open up opportunities for rationally designing hierarchical electrocatalysts for practical water splitting or diverse applications.     

Overall Water Splitting Catalyzed Efficiently by an Ultrathin Nanosheet‐Built,Hollow Ni3S2‐Based Electrocatalyst

Making highly efficient catalysts for an overall ?water splitting reaction is vitally important to bring solar/electrical‐to‐hydrogen energy conversion processes into reality. Herein, the synthesis of ultrathin nanosheet‐based, hollow MoO_x/Ni₃S₂ composite microsphere catalysts on nickel foam, using ammonium molybdate as a precursor and the triblock copolymer pluronic P123 as a structure‐directing agent is reported. It is also shown that the resulting materials can serve as bifunctional, non‐noble metal electrocatalysts with high activity and stability for the hydrogen evolution reaction (HER) as well as the oxygen evolution reaction (OER). Thanks to their unique structural features, the materials give an impressive water‐splitting current density of 10 mA cm^?2 at ≈1.45 V with remarkable durability for >100 h when used as catalysts both at the cathode and the anode sides of an alkaline electrolyzer. This performance for an overall water splitting reaction is better than even those obtained with an electrolyzer consisting of noble metal‐based Pt/C and IrO_x/C catalytic couple—the benchmark catalysts for HER and OER, respectively.     

Hierarchical Porous Ni3S4 with Enriched High‐Valence Ni Sites as a Robust Electrocatalyst for Efficient Oxygen Evolution Reaction

Electrochemical water splitting is a common way to produce hydrogen gas, but the sluggish kinetics of the oxygen evolution reaction (OER) significantly limits the overall energy conversion efficiency of water splitting. In this work, a highly active and stable, meso–macro hierarchical porous Ni₃S₄ architecture, enriched in Ni³⁺ is designed as an advanced electrocatalyst for OER. The obtained Ni₃S₄ architectures exhibit a relatively low overpotential of 257 mV at 10 mA cm^?2 and 300 mV at 50 mA cm^?2. Additionally, this Ni₃S₄ catalyst has excellent long‐term stability (no degradation after 300 h at 50 mA cm^?2). The outstanding OER performance is due to the high concentration of Ni³⁺ and the meso–macro hierarchical porous structure. The presence of Ni³⁺ enhances the chemisorption of OH^?, which facilitates electron transfer to the surface during OER. The hierarchical porosity increases the number of exposed active sites, and facilitates mass transport. A water‐splitting electrolyzer using the prepared Ni₃S₄ as the anode catalyst and Pt/C as the cathode catalyst achieves a low cell voltage of 1.51 V at 10 mA cm^?2. Therefore, this work provides a new strategy for the rational design of highly active OER electrocatalysts with high valence Ni³⁺ and hierarchical porous architectures.     

In Situ Assembly of MoSx Thin-Film through Self-Reduction on p-Si for Drastic Enhancement of Photoelectrochemical Hydrogen Evolution

Strong coupling between the Si photocathode and a low-cost cocatalyst is of great significance for enhancing the photoelectrochemical hydrogen evolution. Here, a facile method is proposed to in situ assemble amorphous MoS_x (a-MoS_x) thin-film onto a single crystal p-Si through a self-reduction mechanism to achieve strong coupling. In the process of self-reduction, the (MoS₄)²⁻ anion is reduced to form a-MoS_x by the oxidation of H–Si to form SiO_x, which is etched further to form H–Si again in the hydrofluoric aqueous solution. The cyclic formation of H–Si and SiO_x plays a decisive role in the continuous deposition of a-MoS_x and provides a unique way to synthesize metal sulfides. Such a-MoS_x/p-Si photocathode exhibits an excellent activity, achieving the optimal onset potential of +0.31 V_RHE and the current density of −28.2 mA cm⁻² at 0 V_RHE with a Faradaic efficiency close to 98%, respectively, outperforming the thermally exfoliated 2H-MoS₂ and 1T-MoS₂ cocatalysts on p-Si and comparable to the previous studies. The proposed method for uniform deposition at room temperature is simple to carry out and can be used for fabricating other Si-based photoelectrodes.     

In Situ Construction of Ni/Ni0.2Mo0.8N Heterostructure to Enhance the Alkaline Hydrogen Oxidation Reaction by Balancing the Binding of Intermediates

The inferior activity of hydrogen oxidation reaction (HOR) in alkali severely hampers the deployment of Ni catalysts in the promising anion exchange membrane fuel cells (AEMFCs), due to the unbalanced binding energies of hydrogen (HBE) and hydroxyl (OHBE) species. Ni-Mo alloy and nickel nitride have been proven to improve the Ni-based activities of HOR but they still can be further enhanced. Because it sacrifices the HBE for enlarging OHBE. Herein, it is reported that the activity can be further improved by constructing heterostructure between Ni nanoparticles (NPs) and nitride of Ni-Mo alloy (Ni_0.2Mo_0.8N) by an in situ synthetic strategy. The in situ prepared reduced graphene oxide (rGO) supported heterostructure (Ni/Ni_0.2Mo_0.8N/rGO) possesses the state-of-the-art activity (overpotential of 100 mV to achieve 2.9 mA cm⁻²), faster kinetics (kinetics current density of 11.20 mA cm⁻² and exchange current density of 2.74 mA cm⁻²), and ultrahigh durability (maintaining the current densities for over 40 h or 10000 cycles). Detailed characterizations together with density functional theory simulations reveal that the tuned d-band electronic structures optimize and balance the HBE and OHBE, facilitating the HOR process on the as-fabricated heterostructured catalyst.     

Multicomponent Intermetallic Nanoparticles on Hierarchical Metal Network as Versatile Electrocatalysts for Highly Efficient Water Splitting

Developing high-efficiency and cost-effective alloy catalysts toward hydrogen-evolution reaction (HER) is crucial for large-scale hydrogen production via electrochemical water splitting, but conventional single-principal-element alloy design usually causes insufficient activity and durability of state-of-the-art multimetallic catalysts based on non-precious transition metals. Herein, we report multicomponent intermetallic Mo(NiFeCo)₄ nanoparticles seamlessly integrated on hierarchical nickel network (Mo(NiFeCo)₄/Ni) as robust hydrogen-evolution electrocatalysts with remarkably improved activity and durability by making use of iron and cobalt atoms partially substituting nickel sites to form high-entropy NiFeCo sublattice in intermetallic MoNi₄ matrix, which serve as bifunctional electroactive sites for both water dissociation and adsorption/combination of hydrogen intermediate and improves thermodynamic stability. By virtue of bicontinuous nanoporous nickel skeleton facilitating electron/ion transportation, self-supported nanoporous Mo(NiFeCo)₄/Ni electrode exhibits exceptional HER electrocatalysis, with low Tafel slope (≈35 mV dec⁻¹), high current density (≈2300 mA cm⁻²) at low overpotential (200 mV) and long-term durability in 1 m KOH. When coupled to its electrooxidized and nitrified derivative for oxygen-evolution reaction, their alkaline water electrolyzers operate with a superior overall water-splitting output, outperforming the one constructed with commercially available noble-metal-based catalysts. These electrochemical properties make it an attractive candidate as electrocatalyst in alkaline water electrolysis for large-scale hydrogen generation.     

Atomic-Level Surface Engineering of Nickel Phosphide Nanoarrays for Efficient Electrocatalytic Water Splitting at Large Current Density

Designing high-performance and cost-effective electrocatalysts for water splitting at high current density is pivotal for practical industrial applications. Herein, it is found that atomic-level surface engineering of self-supported nickel phosphide (NiP) nanoarrays via a facile cation-exchange method can substantially regulate the chemical and physical properties of catalysts by introducing Co atoms. Such surface-engineered Ni_xCo_1–xP endows several aspects of merits: i) rough nanosheet array electrode structure accessible to diffusion of electrolytes and release of gas bubbles, ii) enriched P vacancies companied by Co doping and thus increased active sites, and iii) the synergy of Ni₅P₄ and NiP₂ beneficial to catalytic activity enhancement. By virtue of finely controlling the Co contents, the optimal Ni_0.96Co_0.04P electrode achieves remarkable bifunctional electrocatalytic performance for overall water splitting at a large current density of 1000 mA cm⁻², showing overpotentials of 249.7 mV for hydrogen evolution reaction and 281.7 mV for oxygen evolution reaction. Furthermore, the Ni_0.96Co_0.04P electrode at 500 mA cm⁻² exhibits an ultralow potential (1.71 V) and ultralong durability (500 h) for overall water splitting. This study implies that the atomic-level surface engineering of the electrode materials offers a viable route for gaining high-performance catalysts for water splitting at large current density.     

Bifunctional Nickel Phosphide Nanocatalysts Supported on Carbon Fiber Paper for Highly Efficient and Stable Overall Water Splitting

Self‐supported electrodes comprising carbon fiber paper (CP) integrated with bifunctional nickel phosphide (Ni‐P) electrocatalysts are fabricated by electrodeposition of Ni on functionalized CP, followed by a convenient one‐step phosphorization treatment in phosphorus vapor at 500 °C. The as‐fabricated CP@Ni‐P electrode exhibits excellent electrocatalytic performance toward hydrogen evolution in both acidic and alkaline solutions, with only small overpotentials of 162 and 250 mV, respectively, attaining a cathodic current density of 100 mA cm^?2. Furthermore, the CP@Ni‐P electrode also exhibits superior catalytic performance toward oxygen evolution reaction (OER). An exceptionally high OER current of 50.4 mA cm^?2 is achieved at an overpotential of 0.3 V in 1.0 m KOH. The electrode can sustain 10 mA cm^?2 for 180 h with only negligible degradation, showing outstanding durability. Detailed microstructural and compositional studies reveal that upon OER in alkaline solution the surface Ni‐P is transformed to NiO covered with a thin Ni(OH)_x layer, forming a Ni‐P/NiO/Ni(OH)_x heterojunction, which presumably enhances the electrocatalytic performance for OER. Given the well‐defined bifunctionality, a full alkaline electrolyzer is constructed using two identical CP@Ni‐P electrodes as cathode and anode, respectively, which can realize overall water splitting with efficiency as high as 91.0% at 10 mA cm^?2 for 100 h.     

Amino Acid-Induced Interface Charge Engineering Enables Highly Reversible Zn Anode

Despite the impressive merits of low-cost and high-safety electrochemical energy storage for aqueous zinc ion batteries, researchers have long struggled against the unresolved issues of dendrite growth and the side reactions of zinc metal anodes. Herein, a new strategy of zinc-electrolyte interface charge engineering induced by amino acid additives is demonstrated for highly reversible zinc plating/stripping. Through electrostatic preferential absorption of positively charged arginine molecules on the surface of the zinc metal anode, a self-adaptive zinc-electrolyte interface is established for the inhibition of water adsorption/hydrogen evolution and the guidance of uniform zinc deposition. Consequently, an ultra-long stable cycling up to 2200 h at a high current density of 5 mA cm⁻² is achieved under an areal capacity of 4 mAh cm⁻². Even cycled at an ultra-high current density of 10 mA cm⁻², 900 h-long stable cycling is still demonstrated, demonstrating the reliable self-adaptive feature of the zinc-electrolyte interface. This work provides a new perspective of interface charge engineering in realizing highly reversible bulk zinc anode that can prompt its practical application in aqueous rechargeable zinc batteries.