Ultrathin MoSSe alloy nanosheets anchored on carbon nanotubes as advanced catalysts for hydrogen evolution

The activity of transition metal dichalcogenides (TMD) toward hydrogen evolution reaction (HER) derives from the active sites at the edges, but the basal surface still remain catalytic insert. Herein, ultrathin MoSSe alloy nanosheets array on multiwalled carbon nanotubes (MWCNTs) to form a core shell structure via a simple solvothermal process. These three-dimensional (3D) MoSSe hybrids show a high activity in hydrogen evolution reaction (HER) with a small Tafel slope of 38 mV dec⁻¹ and a low overpotential of 102 mV at 10 mA cm⁻². In addition, their HER activity remains remarkably stable without significant decay after 100 h polarization. Such superior catalytic HER activity springs from the 3D hierarchical heterostructure, which is abundant of catalytic edge sites, and the alloy effect between S and Se, which will create huge defects and strain to form vacancy sites on the basal plane. This strategy may open a new avenue toward the development of nonprecious high-performance HER catalysts.     

NiCoP–CoP heterostructural nanowires grown on hierarchical Ni foam as a novel electrocatalyst for efficient hydrogen evolution reaction

The design and manufacture of effective non-noble metal catalysts for the H₂ evolution reaction (HER) are urgent for realizing a cost-effective hydrogen production. We report herein on flower-like structures consisting of NiCoP–CoP heterostructural nanowires grown directly on the hierarchically porous nickel framework (NiCoP–CoP/Ni/NF) to achieve a highly efficient HER in alkaline solution (1.0 M KOH). The NiCoP–CoP/Ni/NF is synthesized by electrodeposition of porous Ni layers on Ni foam, followed by simple hydrothermal reaction and phosphorization. For HER, the binder-free NiCoP–CoP/Ni/NF electrode can reach 10 mA cm^?2 current density at a quite low overpotential of 49 mV, because of the combination of porous Ni layers and highly active NiCoP–CoP nanowires. In addition, the NiCoP/CoP heterostructures exhibited remarkable stability under the long-term durability test. This work provides a new strategy that combines electrodeposition and hydrothermal reaction to synthesize effective HER catalysts.     

CoP/Ni2P heteronanoparticles integrated with atomic Co/Ni dual sites for enhanced electrocatalytic performance toward hydrogen evolution

Transition metal phosphides (TMPs) have attracted considerable attention as an advanced electrocatalyst for hydrogen evolution reaction (HER). Nevertheless, the catalytic efficiency of single-component TMPs is still restricted that cannot endure long-term running and easy to be corroded especially under harsh conditions. In this work, a multicomponent electrocatalyst combined with CoP/Ni₂P heteronanoparticles and Co/Ni single-atom active sites (denoted as N–C@CoP/Ni₂P) is rational designed and prepared. The obtained N–C@CoP/Ni₂P electrode material exhibits enhanced performance with the overpotential of 153 mV at 10 mA cm^?2, and the small Tafel value of 53.01 mV dec^?1 in 0.5 M H₂SO₄, and a satisfied result is obtained in basic media as well. The outstanding HER performance is mainly benefiting from the synergistic effect between CoP and Ni₂P, and the highly catalytic faction of atomic Co/Ni dual sites. Furthermore, a powerful conductive network fabricated by N-doped carbon skeleton and in-situ grown CNTs improves the conductivity of catalyst. Such a stereoscopic 3D nanostructure is also facile to accelerate the shuttle of electrons and ions.     

Superhydrophilic 3D peony flower-like Mo-doped Ni2S3@NiFe LDH heterostructure electrocatalyst for accelerating water splitting

Constructing highly efficient nonprecious electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is essential to improve the efficiency of overall water splitting, but still remains lots of obstacles. Herein, a novel 3D peony flower-like electrocatalyst was synthesized by employing Mo–Ni₂S₃/NF nanorod arrays as scaffolds to in situ growth ultrathin NiFe LDH nanosheets (Mo-Ni₂S₃@NiFe LDH). As expected, the novel peony flower-like Mo–Ni₂S₃@NiFe LDH displays superior electrocatalytic activity and stability for both OER and HER in alkaline media. Low overpotentials of only 228 mV and 109 mV are required to achieve the current densities of 50 mA cm^?2 and 10 mA cm^?2 for OER and HER, respectively. Additionally, the material remarkably accelerates water splitting with a low voltage of 1.54 V at 10 mA cm^?2, which outperforms most transition metal electrodes. The outstanding electrocatalytic activity benefits from the following these features: 3D peony flower-like structure with rough surface provides more accessible active sites; superhydrophilic surfaces lead to the tight affinity between electrode with electrolyte; metallic Ni substrate and highly conductive Mo–Ni₂S₃ nanorods scaffold together with offer fast electron transfer; the nanorod arrays and porous Ni foam accelerate gas bubble release and ions transmission; the strong interfacial effect between Mo-doped Ni₃S₂ and NiFe LDH shortens transport pathway, which are benefit for electrocatalytic performance enhancement. This work paves a new avenue for construction and fabrication the 3D porous structure to boost the intrinsic catalytic activities for energy conversion and storage applications.     

Boosting hydrogen evolution activity and durability of Pd–Ni–P nanocatalyst via crystalline degree and surface chemical state modulations

Developing efficient, durable, and economical electro-catalysts for large-scale commercialization of hydrogen evolution (HER) is still challenging. Herein, we report for the first time, to the best of our knowledge, a Pd-based ternary metal phosphide as an active and stable HER catalyst. The face-centered-cubic Pd–Ni–P nanoparticles (NPs) annealed at 400 °C show the best HER activity with a low overpotential of 32 mV to realize a current density of 10 mA cm⁻² and a high mass activity of 1.23 mA μg⁻¹_Pd, superior to Pd NPs, Pd–P NPs, Pd–Ni NPs, and Pd–Ni–P NPs annealed under different temperatures. Moreover, this catalyst is also highly stable during 20 h of continuous electrolysis. Notably, the easily fabricated Pd–Ni–P NPs are among the most active Pd-based HER catalysts. This work indicates that Pd-based metal phosphides could be potentially applied as a type of practical HER catalyst and might inform the fabrication of analogous materials for hydrogen-related applications.     

Nanostructural Co–MoS2/NiCoS supported on reduced Graphene oxide as a high activity electrocatalyst for hydrogen evolution in alkaline media

There are many tremendous challenges to enhance the hydrogen evolution reaction (HER) activity of MoS₂. In this study, nanoflower-like Co–MoS₂/NiCoS structure supported on reduced Graphene Oxide (rGO) was rationally developed via a simple hydrothermal route, where the synergistic regulations of both interface structural and electronic conductivity were successfully presented by using controllable interface engineering and Co metal ions doped into MoS₂ nanosheets. Ascribed to the 3D flower-like nanostructure with massive active sites, the interface coupling effect between MoS₂ and Ni–Co–S phase, and Co-doped MoS₂ can modulate its surface electronic density. The optimal Co–MoS₂/NiCoS/rGO hybrid exhibits excellent HER activity in 1.0 M KOH, with a small overpotential (η₁₀, 84 mV) at 10 mA cm^?2 and a low Tafel slope (46 mV dec^?1), accompanied by good stability. This work provides an effective route to produce other electrocatalysts based on interface structure and electronic conductivity engineering for HER in the future.     

Facile synthesis of hierarchical Nb-Doped Mo–Ni–S nanospheres as efficient electrocatalyst toward hydrogen generation in alkaline media

Exploring highly-efficient and inexpensive electrocatalysts toward hydrogen evolution reaction (HER) in alkaline electrolyte act as pivotal role on boosting the development of hydrogen energy. Doping strategy has been regarded as an effective approach to accelerate electrocatalytic kinetics. Herein, transition metal doping method is applied to develop hierarchical molybdenum-nickel bimetallic sulfide nanospheres for HER. The unique spherical structure and synergistic effects between different elements are favorable for improving the electrocatalytic performance by exposing abundant active sites and electronic interactions. Therefore, the synthesized Nb–Mo–Ni–S (Nb-MNS) exhibits outstanding HER performance with overpotentials of 49 mV and 135 mV to deliver 10 mA cm^?2 and 100 mA cm^?2, respectively. Significantly, Nb-MNS displays superior stability of 48 h with the current densities changed from 40 mA cm^?2 to 120 mA cm^?2. This work provides a promising avenue to design transition metal sulfides for energy conversion reactions.     

Mo-incorporated three-dimensional hierarchical ternary nickel-cobalt-molybdenum layer double hydroxide for high-efficiency water splitting

Flowers-like 3D hierarchical ternary NiCoMo-layered double hydroxide (NiCoMo-LDH) spheres have been fabricated in substrate-free route via a one-pot hydrothermal method and utilized as efficient electrocatalysts for the OER and HER. The well-structured 3D hierarchical flowers were composed of numerous two-dimensional nanosheets, which inherently possess considerable electrochemical active sites, thereby enhancing catalytic activity. NiMo and CoMo binary LDHs, with similar morphology, were also prepared to illustrate the efficiency of the ternary LDH. The results indicate higher electrocatalytic activity for the ternary LDH as compared to binary LDHs under alkaline conditions. The NiCoMo-LDH required an overpotential as low as 202 and 93 mV to deliver a constant anodic and cathodic current density of 10 mA cm^?2 for the OER and HER, respectively. Furthermore, the NiCoMo-LDH exhibited remarkable HER activity, affording a low overpotential of 198 mV at a current density of ?100 mA cm^?2. Moreover, it could offer a stable current density of 10 mA cm^?2 for overall water splitting at 1.62 V in 1 M KOH with long-term stability for 20 h. The double-layer capacitance (C_dl) value indicated that the NiCoMo-LDH significantly influenced interface conductivity and the electrochemical active surface area. The ternary NiCoMo-LDH electrode yielded low Tafel slope values of 54 and 51 mVdec^?1 for the OER and HER. Owing to the efficient incorporation of Ni, Co, and Mo in a layered structure, synergetic effect, and high electrochemical surface area, the NiCoMo-LDH exhibited remarkable electrocatalytic activity. Such eco-friendly ternary LDHs can be used in rechargeable metal–air batteries for industrial applications.     

A novel Ni–La-Nd-Y flim on Ni foam to enhance hydrogen evolution reaction in alkaline media

The exploration of non-precious metal catalysts has always been a hot topic. Here, a new type of Ni–La-Nd-Y film was electrodeposited on nickel foam (NF). The Ni–La-Nd-Y film shows outstanding HER activity and stability under alkaline conditions. La₂NiO₄ makes the electrode surface present a regular layered structure, which greatly increases the number of electrochemically active sites. Ni–La-Nd-Y only needs 46 mV overpotential driving current density of 10  mA cm^?2 in 1MKOH solution, which is very close to the HER performance of metal Pt. By doping rare earth elements and taking advantage of the shrinkage characteristics of lanthanides, this work took advantage of the shrinkage characteristics of the lanthanide series and found new ideas for improving catalysts through the combination of different rare earth elements.     

Nickel-doped MoSe2 nanosheets with Ni–Se bond for alkaline electrocatalytic hydrogen evolution

Molybdenum diselenide (MoSe₂) is a potential catalytic material for the electrocatalytic hydrogen evolution reaction (HER). However, due to the low density of its active sites, MoSe₂ nanosheets feature high overpotential in HER, which limits its practical application. This describes the method of doping the Ni in MoSe₂ nanosheets to increase active sites. The NiO₂ evenly dispersed on MoSe₂ by ethanol solution reduces to ~4 nm Ni nanoclusters under annealing process, which is firmly adhered to MoSe₂ nanosheets with Ni–Se bond. The electrochemical active surface area of Ni-doped MoSe₂ expands, proving that Ni dopants produce more activity sites in MoSe₂ nanosheets. The overpotential of MoSe₂ (at 10 mA cm⁻²) decreases from 335 mV to 181 mV with 4.5 at.% Ni doped in 1 M KOH. The Ni–MoSe₂ also characterizes excellent stability for 12 h with the formation of Ni–Se bond. The study of doping Ni in MoSe₂ nanosheets is of great guiding significance to the design and production of non-noble electrocatalysts for HER in alkaline media.     

Hollow Fe/Ni–CoTe@NCFs nanoarchitecture derived from MOF@MOF as high-efficiency electrocatalysts for boosting oxygen evolution reaction

To improve the oxygen evolution reaction (OER) catalytic efficiency of non-noble-metal-based catalysts, researchers have made great endeavors to adjust the compositions, morphologies and configuration of material. In this work, a dual-metal-organic frameworks (MOFs)-assisted fabrication hierarchical and hollow N-doped carbon nanoframes (NCFs) decorated with Fe/Ni-codoped CoTe nanocomposite catalyst (Fe/Ni–CoTe@NCFs) is reported. Starting from MOF-in-MOF composite precursors, the design and fabrication of Fe/Ni–CoTe by the strategies: i.e, hydrothermal precipitation, chemical etching and low-temperature tellurization, and high-temperature pyrolysis steps. Newly designed catalyst (Fe/Ni–CoTe@NCFs) performs superior OER catalytic activity to afford 10 mA cm⁻² at the overpotential of 287 mV with a small Tafel slope of 52.3 mV dec⁻¹. The frame-like hollow core-shell nanostructures with ample channels into the internal volume and high double-layer capacitance provide the large catalytic active surface area and increase more actives sites. The cooperative effects between alloy and metal telluride, as well as hollow carbon shell promote the activity of OER. Therefore, this study offers a catalyst with great potential for OER and provides the possibility for the application of transition metal tellurides in electrocatalysis.     

Nanoarchitectonics of bacterial cellulose with nickel-phosphorous alloy as a binder-free electrode for efficient hydrogen evolution reaction in neutral solution

Developing low-cost and efficient electrodes for hydrogen evolution reaction (HER) under neutral electrolytes remains an unattained milestone. We report a highly performing binder-free electrode through electroless deposition of Ni–P nanoparticles on bacterial cellulose (BC). Not needing carbonization to provide the electric conductivity, BC can maintain its excellent mechanical properties and thin fiber microstructure. The nanometric cellulose fibers facilitate the formation of small Ni–P nanoparticles, leading to more catalytic active sites. The obtained Ni–P/BC electrode presents remarkable HER activity with an overpotential of only 161 mV at 10 mA cm^?2 and a low Tafel slope (141 mV dec^?1) in 1 M potassium phosphate-buffered saline (pH = 7) electrolyte. Besides, Ni–P/BC also exhibits good stability for 24 h at 10 mA cm^?2. This binder-free, low-cost, and easily fabricated electrode holds excellent promise for HER applications in benign neutral environments.     

Ni–P alloy@carbon nanotubes immobilized on the framework of Ni foam as a 3D hierarchical porous self-supporting electrode for hydrogen evolution reaction

The development of self-supporting electrodes that exhibited both high efficiency and good durability remained a challenge in the field of hydrogen energy utilisation. Here, we designed a self-supporting 3D hierarchical porous electrode by filling carbon nanotubes (CNTs) loaded with Ni–P alloy into the framework of nickel foam (NF). Firstly, CNTs were decorated with a catalytically active Ni–P alloy via electroless plating (Ni–P@CNTs). Then, the Ni–P@CNTs were filled and anchored onto the framework of NF via electroplating to synthesise a self-supporting electrode (Ni–P@CNTs/NF). The Ni–P@CNTs/NF exhibited an excellent catalytic performance toward the hydrogen evolution reaction (HER) in 1 M KOH electrolyte, with an overpotential of 53 mV at 10 mA cm^?2, a small Tafel slope of 101.56 mV dec^?1 and excellent long-term durability. This facile and effective strategy might provide a new path to the design of self-supporting electrodes with enhanced HER catalytic.     

One-step potentiostatic electrodeposition of Ni–Se–Mo film on Ni foam for alkaline hydrogen evolution reaction

Exploring efficient, abundant, low-cost and stable materials for hydrogen evolution reaction (HER) is highly desired but still a challenging task. Herein, Ni–Se–Mo electrocatalysts supported on nickel foam (NF) substrate were synthesized by a facile one-step electrodeposition method. The Ni–Se–Mo film presents high electrocatalytic activity and stability toward HER, with a low overpotential of 101 mV to afford a current density of 10 mA cm⁻² in 1.0 M KOH medium. Such excellent HER performance of Ni–Se–Mo film induced by the synergistic effects from Mo-doped Ni–Se film leads to the fast electron transfer. This work provides the validity of interface engineering strategy in preparing highly efficient transition metal chalcogenides based HER electrocatalysts.     

WS2/NiSx heterojunction nanosheet clusters: A highly efficient electrocatalyst for hydrogen evolution reaction

The development of highly active and stable electrocatalysts is essential to solve energy and environmental problems and realize sustainable social and economic development. Herein, we synthesized a bimetallic sulfide material by a kinetically controlled low-temperature solid-phase reaction. The bimetallic sulfide improves the conductivity of the electrocatalysts by optimized electronic structure, and the coupling effect at the heterogeneous interface of WS₂ and NiS_x increases the charge density on the S site at W–S–Ni, making it easier for the electrocatalysts to trap the active material in solution. In addition, nanosheet clusters expose abundant catalytic sites, which together improve hydrogen evolution reaction (HER) for catalytic activity. Optimized WS₂/NiS_x composite show near-precious metal catalyst activity with an overpotential at 10 mA cm^?2 of only 72 mV in alkaline media, which exhibits excellent catalytic stability and outperforms most non-precious metal electrocatalysts.     

Carbon nanorod supported metal alloy nanocubes using polydopamine as location reagent for water splitting

Transition metal catalysts were supposed to be the most likely substitute for commercial noble metal catalysts, and the development of highly active and long-term catalyst for water splitting are the future trend. Herein, Ni rectangular nitrogen doped carbon nanorods@Fe–Co nanocubes (Ni-CNRs@Fe–Co cubes) were fabricated via a facile template-free method. This simple strategy not only realizes the structure tailoring, but also achieves high-quality nitrogen-doping. Specifically, nickel dimethylglyoxime [Ni(dmg)₂] with rectangular rodlike structure was firstly synthesized by solution method, then metal-organic frameworks Fe–Co nanocube with different contents were loaded on rectangular carbon nanorods with polydopamine as the locating and the connecting agent, and finally Ni-CNRs@xFe-Co cubes were obtained by a one-step calcination. A series of electrochemical tests were researched on materials with different metal contents in the 1 M KOH solution. The Ni-CNRs@Fe–Co cubes show excellent electrocatalytic activity in the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). For HER and OER, the Tafel slopes were 83.3 mV dec⁻¹ and 71 mV dec⁻¹, the onset potential were −167 mV and 1.62 V, and reached the current densities of 10 mA cm⁻², the overpotential just needed 196 mV and 433 mV, respectively. This novel synthetic strategy will provide a template-free way for cheap electrocatalysts of non-precious metal for OER and HER.     

Ni,Zn Co-doping ZIF-67-derived electrocatalyst based on CNT film for efficient overall water splitting

Water electrolysis has been acknowledged as a renewable, scalable, and effective way of producing hydrogen. However, for water splitting, efficient and noble metal-free electrocatalysts were lacking. Here, a Co–Ni–Zn porous three-dimension N-doped carbonization structure on the carbon nanotube film (CNTF) was synthesized through a metal organic frameworks (MOFs) annealing procedure. The porous morphology, caused by the evaporation of zinc at high temperatures, enhances the interaction between the catalysts and electrolyte, and the self-supporting structure minimizes the contact resistance between the catalysts and the substrate, which reduces obstructions during current flow. More active sites, multiple mesopores, and high conductivity are all features of this composite structure. It can achieve a small overpotential of 112 mV and 270 mV at a current density of 10 mA cm⁻², respectively, for hydrogen and oxygen evolution reactions (HER and OER). At a current density of 10 mA cm⁻², the Co–Ni–Zn/NCNTF has an external voltage of 1.58 V and is very durable for overall water splitting.     

Ruthenium-manganese phosphide nanohybrid supported on graphene for efficient hydrogen evolution reaction in acid and alkaline conditions

Transition metal phosphides (TMPs) have been proved to be promising, economical and effective catalysts for hydrogen evolution reaction (HER). Precious metals with transition metals alloying can appropriately adjust the adsorption energy, which is an effective solution for greatly reducing the cost of noble metal catalysts and improving their inherent performance. Herein, a simple method was employed to synthesize MnRuPOGO-500 nano-catalysts with a particle size of about 5 nm, which showed excellent HER performance under both acid and basic media. In acidic solution, the optimal catalyst displayed the overpotential of HER to reach 10 mA cm^?2 with 109 mV, a small Tafel slope of 38.55 mV dec^?1 and long-time durability of 60 h. Especially in alkaline medium, the low overvoltage of 27 mV, a small Tafel slope of 57.35 mV dec^?1 and continuing stability of 48 h were further achieved. Meanwhile, we can find that manganese has negligible HER activity, but the doping of manganese generates a synergistic modulation effect in the MnP–Ru₂P alloy, thereby improving the HER performance of the catalyst. This paper brings a simple scheme and unique insights to the design of transition metals and platinum group metals (PGMs) phosphide alloy electrocatalysts.     

Boosting activity and stability by coupling Pt–Ni nanoparticles with La-modified flexible carbon nanofibers for hydrogen evolution reaction

Platinum (Pt) is considered as the most efficient catalyst for hydrogen evolution reaction (HER) with a nearly zero overpotential, but it is limited by the high cost and poor stability. Herein, we report an efficient electrocatalyst of Pt–Ni alloy nanoparticles (NPs) supported on the La-modified flexible carbon nanocomposite fibers (PtNi@La-CNFs) for HER. The rare earth metal oxide in the catalyst has a structure-effect relationship with the carbon fibers to form a flexible fiber membrane. Experimental results show that the macroscopic and microscopic properties of carbon nanocomposite fibers can be optimized by doping La₂O₃, and the Pt–Ni NPs can be anchored effectively. The Pt₁Ni₁@La-CNFs electrocatalyst exhibits a small overpotential of 32 mV to achieve current density of 10 mA cm^?2 with a low Tafel slope of 51 mV dec^?1 in alkaline medium, outperforming that of Pt@La-CNFs and the commercial Pt/C catalyst. This study reveals that the multiple coupling effect of rare earth compound, precious metal, and transition metal in composite catalyst can tailor its the electronic configuration, and results in an enhanced HER performance. This work opens up a novel approach to design high active and low cost Pt-based HER catalysts.     

Self-adaptive amorphous Co2P@Co2P/Co-polyoxometalate/nickel foam as an effective electrode for electrocatalytic water splitting in alkaline electrolyte

Noble-metal-free transition metal based phosphides (TMPs) display great potential as candidates to replace the state-of-the-art noble metal-based catalysts for electronic water splitting. In this study, amorphous Co₂P was decorated on Co-polyoxometalate (POM) and conductive cobalt phosphide forming integrated Co₂P@ Co₂P/Co-POM/NF electrode, through in suit growth, low-temperature phosphating and electrocatalytic self-adaption pathway by the stripping of superficial Co-POM when subjected to persistent bubbles. The fantastic design simultaneously offers excellent electrical conductivity for fast electron transfer, a large surface area with numerous active edge sites and a conductive current collector facilitating mass transfer and gas release. The electrode showed high catalytic activity, requiring overpotential of 130 mV for HER to achieve a current density of 50 mA/cm², 336 mV for OER to achieve a current density of 50 mA/cm², affording a water-splitting current density of 10 mA/cm² at a low cell voltage of 1.6 V. The results and facile synthesis method also offer an exciting avenue for the design of amorphous phase TMPs on a current collector with high specific area and excellent electrical conductivity for energy storage and conversion devices.