Ruthenium Nanoparticles Anchored on Graphene Hollow Nanospheres Superior to Platinum for the Hydrogen Evolution Reaction in Alkaline Media.

The design and construction of highly efficient and stable Pt-free catalysts for the electrocatalytic hydrogen evolution reaction (HER) in alkaline media is extremely desirable. Herein, a novel hybrid of ruthenium (Ru) nanoparticles anchored on graphene hollow nanospheres (GHSs) is synthesized by a template-assisted strategy. The combination of ultrafine Ru nanoparticles and hollow spherical support endows the resultant Ru/GHSs an extraordinary catalytic performance with a low overpotential of 24.4 mV at a current density of 10 mA cm-2, a small Tafel slope of 34.8 mV dec-1, as well as long-term stability in 1.0 M KOH solution, which is, to our knowledge, superior to commercial 20% Pt-C catalyst and most of the state-of-the-art HER electrocatalysts reported. Remarkably, this work provides a new route for the development of other metal-based HER electrocatalysts for energy-related applications.

Assembly of Multifold Helical Polyoxometalate-Based Metal-Organic Frameworks as Anode Materials in Lithium-Ion Batteries.

For exploring the multifold helical fabrication of polyoxometalate (POM)-based hybrid compounds, four POM-based crystalline compounds with different meso-helices, H3[Ag27(trz)16(H2O)6][SiW12O40]2·5H2O (1), H[Ag27(trz)16(H2O)4][PW12O40]2·2H2O (2), [Ag23(trz)14(H2O)2][HSiW12O40] (3), and [Ag23(trz)14(H2O)2][PW12O40] (4), were successfully isolated by using the delicate 1,2,3-triazole ligand and silver ions in this work. Crystal analysis reveals that compounds 1 and 2 and compounds 3 and 4 are isomorphous and display 2-/4-fold mixed meso-helices and simple 2-fold meso-helices, respectively. In addition, due to the reversible multielectron redox behavior and electron storage functions of POMs, compounds 1 and 3 were studied as anode materials in lithium-ion batteries (LIBs). Compounds 1 and 3 show very high lithiation capacities (1356 and 1140 mAh g-1, respectively) in the initial cycle, which are much higher than those of (NBu4)4[SiW12O40] and commercial graphite at the current density of 100 mA g-1. More importantly, both compounds also show good stable performance after 100 cycles.

Polyoxometalate-Incorporated Metallapillararene/Metallacalixarene Metal-Organic Frameworks as Anode Materials for Lithium Ion Batteries.

A series of remarkable crystalline compounds containing metallapillararene/metallacalixarene metal-organic frameworks (MOFs), [Ag5(pyttz)3·Cl·(H2O)][H3SiMo12O40]·3H2O (1), [Ag5(trz)6][H5SiMo12O40] (2), [Ag5(trz)6][H5GeMo12O40] (3), and [Ag5(trz)6][H4PW12O40] (4) (pyttz = 3-(pyrid-4-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl, trz = 1,2,4-triazole), have been obtained by using a simple one-step hydrothermal reaction of silver nitrate, pyttz for 1 and trz for 2-4, and Keggin type polyoxometalates (POMs). Crystal analysis reveals that Keggin POMs have been successfully incorporated in the windows of the metallapillararene/metallacalixarene MOFs in compounds 1-4. In addition, the Keggin silicomolybdenate-based hybrid compounds 1 and 2 were used as anode materials in lithium ion batteries (LIBs), which exhibited promising electrochemical performance with the first discharge capacities of 1344 mAh g-1 for 1 and 1452 mAh g-1 for 2, and this stabilized at 520 mAh g-1 for 1 and 570 mAh g-1 for 2 after 100 cycles at a current density of 100 mA g-1. The performances are better than that of (NBu4)4[SiMo12O40] matrix and commercial graphite anodes.

Multicomponent nickel-molybdenum-tungsten-based nanorods for stable and efficient alkaline seawater splitting.

The electrolysis of seawater for hydrogen production holds promise as a sustainable technology for energy generation. Developing water-splitting catalysts with low overpotential and stable operation in seawater is essential. In this study, we employed a hydrothermal method to synthesize NiMoWOX microrods (NiMoWOX@NF). Subsequently, an annealing process yielded a composite N-doped carbon-coated Ni3N/MoO2/WO2 nanorods (NC@Ni3N/MoO2/WO2@NF), preserving the ultrahigh-specific surface area of the original structure. A two-electrode electrolytic cell was assembled using NC@Ni3N/MoO2/WO2@NF as the cathode and NiMoWOX@NF as the anode, demonstrating exceptional performance in seawater splitting. The cell operated at a voltage of 1.51 V with a current density of 100 mA·cm-2 in an alkaline seawater solution. Furthermore, the NC@Ni3N/MoO2/WO2@NF || NiMoWOX@NF electrolytic cell exhibited remarkable stability, running continuously for over 120 h at a current of 1100 mA·cm-2 without any observable delay. These experimental results are corroborated by density functional theory calculations. The NC@Ni3N/MoO2/WO2@NF || NiMoWOX@NF electrolyzer emerges as a promising option for industrial-scale hydrogen production through seawater electrolysis.

Dual-metal-organic-framework derived CoP/MoP hybrid as an efficient electrocatalyst for acidic and alkaline hydrogen evolution reaction.

Searching for efficient and cost-effective electrocatalysts for hydrogen evolution reaction (HER) is significantly desirable and challenging. Herein, N, P co-doped carbon-encapsulated CoP/MoP hybrid (CoP/MoP@NPC) is fabricated using dual-metal-organic-framework (dual-MOF) as precursor by a simple one-step phosphating process. When applied as an electrocatalyst toward the HER, the as-designed CoP/MoP@NPC hybrid shows efficiently catalytic performance with a lower overpotential of 183 mV to deliver a current density of 10 mA cm-2, smaller Tafel slope of 53.3 mV dec-1 as well as long-time stability for 10 h in 0.5 M H2SO4 owing to the distinctive component and structural advantages. Furthermore, the electrode material also displays enhanced electrocatalytic HER activity in alkaline media. Importantly, this work provides an effective and feasible route for the construction of bimetallic phosphide electrocatalysts toward hydrogen production.

Interfacial engineering of CoP/CoS2 heterostructure for efficiently electrocatalytic pH-universal hydrogen production.

The design and development of high-performance, low-cost catalysts with long-term durability are crucial for hydrogen generation from water electrolysis. Interfacial engineering is an appealing strategy to boost the catalytic performance of electrode materials toward hydrogen evolution reaction (HER). Herein, we report a simple phosphidation followed by sulfidation treatment to construct heterogeneous cobalt phosphide-cobalt sulfide nanowire arrays on carbon cloth (CoP/CoS2/CC). When evaluated as catalysts toward the HER, the resultant CoP/CoS2/CC exhibits efficient pH-universal hydrogen production due to the heterostructure, synergistic contribution of CoP and CoS2, and conductive substrate. To attain a current density of 10 mA cm-2, overpotentials of only 111.2, 58.1, and 182.9 mV for CoP/CoS2/CC are required under alkaline, acidic, and neutral conditions, respectively. In particular, the as-prepared CoP/CoS2/CC shows markedly improved HER electroactivity in 1.0 M KOH, even outperforming commercial Pt-C/CC at a current density of >50 mA cm-2. In addition, the self-assembled CoP/CoS2||NiFe layered double hydroxide electrolyzer demonstrates efficient catalytic performance and long-time stability, excelling the benchmark Pt-C||IrO2. These findings indicate an effective pathway for the fabrication of high-performance heterogeneous electrocatalysts for hydrogen production in the future.

The facile synthesis of FeP/CoP confined in N, P co-doped carbon derived from MOFs for an efficient pH-universal hydrogen evolution reaction.

Electrochemical hydrogen production is greatly limited by the low efficiency, high cost, and poor stability of electrocatalysts. Here, we report a facile one-step method to synthesize nitrogen, phosphorus co-doped carbon encapsulated FeP/CoP derived from dual metal-organic frameworks (FeP/CoP@NPC). Thanks to the synergistic effect of its unique composition and structure, the resultant FeP/CoP@NPC shows excellent catalytic HER performance with low potentials of 198, 286, and 339 mV to achieve a current density of 10 mA cm-2 in acidic, neutral, and alkaline media along with remarkable long-time durability, respectively. More importantly, this work provides an efficient strategy for fabricating high-performance and stable pH-universal catalysts toward hydrogen generation.

Silver decorated nickel-cobalt (oxy)hydroxides fabricated via surface reconstruction engineering for boosted electrocatalytic oxygen evolution and urea oxidation.

Electrochemical water splitting is considered to be a promising renewable hydrogen generation technology but is significantly limited by the kinetically sluggish oxygen evolution reaction (OER) at the anode. Herein, a silver nanoparticle decorated nickel-cobalt (oxy)hydroxide composite is fabricated on nickel foam (Ag@NiCo(OH)x/NF) via electrodeposition followed by spontaneous redox reaction. Benefitting from the synergetic contributions of an amorphous/crystalline phase, abundant artificial heterointerfaces, and a 3D porous architecture, the as-designed Ag@NiCo(OH)x/NF shows substantially enhanced electrocatalytic performance toward the OER and urea oxidation reaction. Impressively, in the urea-assisted alkaline electrolyzer (coupled with commercial Pt/C on NF as the cathode) for hydrogen production, a cell voltage of only 1.49 V is required to deliver a current density of 50 mA cm-2, much lower than that of traditional water splitting (1.69 V). Importantly, this work represents a facile and feasible method to exploit efficient self-supported electrocatalysts toward overall water splitting and urea-rich wastewater purification.

Engineering MoxC nanoparticles confined in N,P-codoped porous carbon hollow spheres for enhanced hydrogen evolution reaction.

N,P-codoped porous carbon hollow nanosphere confining ultrafine molybdenum carbide nanoparticles are designed and prepared through a facile method. By virtue of the distinct composite and structure advantages, the resulting composite shows significantly enhanced electrocatalytic performance toward the hydrogen evolution reaction.

MOF-derived ruthenium-doped amorphous molybdenum dioxide hybrid for highly efficient hydrogen evolution reaction in alkaline media.

Ruthenium-doped amorphous molybdenum dioxide coupled with a reduced graphene oxide hybrid (Ru-MoO2@PC/rGO) is synthesized using polyoxometalate-based MOFs/GO as a precursor. Benefitting from the synergistic effect of numerous exposed active sites, Ru dopants and the introduction of GO, the designed catalyst shows exceptional electrocatalytic performance toward the HER in alkaline media.

Synergistically enhanced hydrogen evolution reaction by ruthenium nanoparticles dispersed on N-doped carbon hollow nanospheres.

Ultrafine Ru nanoparticles dispersed on 3D N-doped carbon hollow nanospheres were firstly prepared by a feasible templating strategy. Due to the synergistic effect of the unique composite and structure, the resulting nanocomposite as a HER catalyst shows extraordinary electrocatalytic performance, superior to that of commercial Pt-C and most previously reported electrocatalysts.

Confined Molybdenum Phosphide in P-Doped Porous Carbon as Efficient Electrocatalysts for Hydrogen Evolution.

Highly efficient electrocatalysts for hydrogen evolution reactions (HER) are crucial for electrochemical water splitting, where high-cost and low-abundance Pt-based materials are the benchmark catalysts for HER. Herein, we report the fabrication of MoP nanoparticles confined in P-doped porous carbon (MoP@PC) via a metal-organic framework-assisted route for the first time. Remarkably, due to the synergistic effects of MoP nanocrystals, P dopant, and porous carbon, the resulting MoP@PC composite exhibits superior HER catalytic activity with an onset overpotential of 97 mV, a Tafel slope of 59.3 mV dec-1, and good long-term durability, which compares to those of most reported MoP-based HER catalysts. Most importantly, the work opens a new route in the development of high-performance nonprecious HER electrocatalysts derived from MOFs.

Highly efficient hydrogen evolution electrocatalysts based on coupled molybdenum phosphide and reduced graphene oxide derived from MOFs.

A coupled hybrid of molybdenum phosphide (MoP) and reduced graphene oxide has been prepared for the first time utilizing Mo-MOFs as precursors through a facile method. The nanocomposite exhibits superior electrocatalytic performance towards the HER, and is one of the best high-performance MoP-based electrocatalysts under acidic conditions reported so far.

Coupled molybdenum carbide and reduced graphene oxide electrocatalysts for efficient hydrogen evolution.

Electrochemical water splitting is one of the most economical and sustainable methods for large-scale hydrogen production. However, the development of low-cost and earth-abundant non-noble-metal catalysts for the hydrogen evolution reaction remains a challenge. Here we report a two-dimensional coupled hybrid of molybdenum carbide and reduced graphene oxide with a ternary polyoxometalate-polypyrrole/reduced graphene oxide nanocomposite as a precursor. The hybrid exhibits outstanding electrocatalytic activity for the hydrogen evolution reaction and excellent stability in acidic media, which is, to the best of our knowledge, the best among these reported non-noble-metal catalysts. Theoretical calculations on the basis of density functional theory reveal that the active sites for hydrogen evolution stem from the pyridinic nitrogens, as well as the carbon atoms, in the graphene. In a proof-of-concept trial, an electrocatalyst for hydrogen evolution is fabricated, which may open new avenues for the design of nanomaterials utilizing POMs/conducting polymer/reduced-graphene oxide nanocomposites.

Nitrogen-doped Fe/Fe3C@graphitic layer/carbon nanotube hybrids derived from MOFs: efficient bifunctional electrocatalysts for ORR and OER.

A novel nitrogen-doped Fe/Fe3C@graphitic layer/carbon nanotube hybrid derived from MOFs has been first fabricated by a facile approach. The hybrid exhibited outstanding bifunctional electrocatalytic activity for ORR and OER, due to the merits of graphitic layer/carbon nanotube structures with highly active N and Fe/Fe3C sites.

Heteroatoms ternary-doped porous carbons derived from MOFs as metal-free electrocatalysts for oxygen reduction reaction.

The nitrogen (N), phosphorus (P) and sulphur (S) ternary-doped metal-free porous carbon materials have been successfully synthesized using MOFs as templates (denoted as NPS-C-MOF-5) for oxygen reduction reaction (ORR) for the first time. The influences of porous carbons from carbonizing different MOFs and carbonization temperature on ORR have been systematically investigated. Due to the synergistic effect of N, P and S ternary-doping, the NPS-C-MOF-5 catalyst shows a higher onset potential as a metal-free electrocatalyst for ORR among the currently reported metal-free electrocatalysts, very close to the commercial Pt-C catalyst. In particular, the kinetic limiting current density of NPS-C-MOF-5 catalyst at -0.6 V is up to approximate -11.6 mA cm(-2), which is 1.2 times higher than that of the commercial Pt-C catalyst. Furthermore, the outstanding methanol tolerance and excellent long-term stability of NPS-C-MOF-5 are superior to those of the commercial Pt-C catalyst for ORR in alkaline media.