Novel nanoporous binary Ag-Ni electrocatalysts for hydrazine oxidation

From an aqueous mixture of Ag（I）-EDTA complex and Ni（II） nitrate, silver and nickel particles were co-deposited on the surface of titanium substrates by the hydrothermal method using hydrazine hydrate as a reduction agent. The prepared titanium-supported nano-scale Ag and Ag-Ni particles （nano Ag/Ti, nano Ag86Ni14/Ti, nano Ag77Ni23/Ti, and nano Ag74Ni26/Ti） exhibit nanoporous 3D network textures. Their electrocatalytic activity towards hydrazine oxidation in alkaline solutions was evaluated by cyclic voltammetry and chronoamperometry. The results show that the four samples present a low onset potential of ca. -0.60 V vs. SCE and considerably high and stable anodic current densities for hydrazine oxidation. Among them, the nano Ag86Ni14/Ti electrode exhibits the highest anodic current density towards hydrazine oxidation, showing an increment of electro-active sites on the nano Ag86Ni14/Ti due to the addition of Ni to Ag particles.

Hydrogen evolution-assisted one-pot aqueous synthesis of hierarchical trimetallic PdNiRu nanochains for hydrazine oxidation reaction

A hydrogen evolution-assisted one-pot aqueous approach was developed for facile synthesis of trimetallic Pd Ni Ru alloy nanochain-like networks（Pd Ni Ru NCNs） by only using KBHas the reductant, without any specific additive（e.g. surfactant, polymer, template or seed）. The products were mainly investigated by transmission electron microscopy（TEM）, X-ray diffraction（XRD） and X-ray photoelectron spectroscopy（XPS）. The hierarchical architectures were formed by the oriented assembly growth and the diffusioncontrolled deposition in the presence of many in-situ generated hydrogen bubbles. The architectures had the largest electrochemically active surface area（ECSA） of 84.32 mgPdthan Pd Ni nanoparticles(NPs,65.23 mgPd), Pd Ru NPs(23.12 mgPd), Ni Ru NPs（nearly zero）, and commercial Pd black(6.01 mgPd), outperforming the referenced catalysts regarding the catalytic characters for hydrazine oxygen reaction（HOR）. The synthetic route provides new insight into the preparation of other trimetallic nanocatalysts in fuel cells.

Selectively nucleotide-derived RuP on N,P-codoped carbon with engineered mesopores for energy-efficient hydrogen production assisted by hydrazine oxidation

Integrating hydrogen evolution reaction(HER)with hydrazine oxidation reaction(HzOR)has an encouraging prospect for the energy-saving hydrogen production,demanding the high-performance bifunctional HER/HzOR electrocatalyst.Ruthenium phosphide/doped carbon composites have exhibited superior activity towardmultiple electrocatalytic reactions.To explore the decent water-soluble precursors containing bothNand P elements is highly attractive to facilely prepare metal phosphide/doped carbon composites.Herein,as one kind ecofriendly biomolecules,adenine nucleotide was first employed to selectively fabricate the highly pure RuP nanoparticles embedded into porous N,P-codoped carbons(RuP/PNPC)with a straightforward“mix-and-pyrolyze”approach.The newly prepared RuP/PNPC only requires 4.0 and−83.0 mV at 10 mA/cm^(2) separately in alkaline HER and HzOR,outperforming most of reported electrocatalysts,together with the outstanding neutral bifunctional performance.Furthermore,the two-electrode alkaline and neutral overall hydrazine splitting both exhibit significant power-efficiency superiority to the corresponding overall water splitting with the voltage difference of larger than 2 V,which can be also easily driven by the fuel cells and solar cells with considerableH2 generation.Our report innovates the N-and P-bearing adenine nucleotide to effortlessly synthesize the high-quality RuP/doped carbon composite catalysts,highly potential as a universal platform for metal phosphide-related functional materials.

Reduction-induced interface reconstruction to fabricate MoNi_(4) - based hollow nanorods for hydrazine oxidation assisted energysaving hydrogen production in seawater

Seawater electrolysis could address the water scarcity issue and realize the grid-scale production of carbon-neutral hydrogen,while facing the challenge of high energy consumption and chloride corrosion.Thermodynamically more favorable hydrazine oxidation reaction(HzOR)assisted water electrolysis is efficiency for energy-saving and chlorine-free hydrogen production.Herein,the MoNi alloys supported on MoO_(2) nanorods with enlarged hollow diameter on Ni foam(MoNi@NF)are synthesized,which is constructed by limiting the outward diffusion of Ni via annealing and thermal reduction of NiMoO_(4) nanorods.When coupling HzOR and hydrogen evolution reaction(HER)by employing MoNi@NF as both anode and cathode in two-electrode seawater system,a low cell voltage of 0.54 V is required to achieve 1,000 mA·cm^(−2) and with long-term durability for 100 h to keep above 100 mA·cm^(−2) and nearly 100%Faradaic efficiency.It can save 2.94 W·h to generate per liter H_(2) relative to alkaline seawater electrolysis with 37%lower energy equivalent input.

Copper nanoparticles/polyaniline-derived mesoporous carbon electrocatalysts for hydrazine oxidation

Copper nanoparticles-decorated polyaniline- derived mesoporous carbon that can serve as noble metal-free electrocatalyst for the hydrazine oxidation reaction （HzOR） is synthesized via a facile synthetic route. The material exhibits excellent electrocatalytic activity toward HzOR with low overpotential and high current density. The material also remains stable during the electrocatalytic reaction for long time. Its good electro- catalytic performance makes this material a promising alternative to conventional noble metal-based catalysts （e.g., Pt） that are commonly used in HzOR-based fuel cells.

Highly active bifunctional catalyst: Constructing FeWO_(4)-WO_(3) heterostructure for water and hydrazine oxidation at large current density

Developing high performance anode catalysts for oxygen evolution reaction (OER) and hydrazine oxidation reaction (HzOR) at large current density is an efficient pathway to produce hydrogen. Herein, we synthesize a FeWO_(4)-WO_(3) heterostructure catalyst growing on nickel foam (FeWO_(4)-WO_(3)/NF) by a combination of hydrothermal and calcination method. It shows good catalytic activity with ultralow potentials for OER (ζ_(10) = 1.43 V, ζ_(1.000) = 1.56 V) and HzOR (ζ_(10) = −0.034 V, ζ_(1.000) = 0.164 V). Moreover, there is little performance degradation after being tested for _(10)0 h at 1,000 (OER) and _(10)0 (HzOR) mA·cm−2, indicating good stability. The superior performance could be attributed to the wolframite structure and heterostructure: The former provides a high electrical conductivity to ensure the electronic transfer capability, and the later induces interfacial electron redistribution to enhance the intrinsic activity and stability. The work offers a brand-new way to prepare good performance catalysts for OER and HzOR, especially at large current density.

Heteroatom-Induced Accelerated Kinetics on Nickel Selenide for Highly Efficient Hydrazine-Assisted Water Splitting and Zn-Hydrazine Battery

Hydrazine-assisted water electrolysis is a promising energy conversion technology for highly efficient hydrogen production.Rational design of bifunctional electrocatalysts,which can simultaneously accelerate hydrogen evolution reaction(HER)/hydrazine oxidation reaction(HzOR)kinetics,is the key step.Herein,we demonstrate the development of ultrathin P/Fe co-doped NiSe_(2) nanosheets supported on modified Ni foam(P/Fe-NiSe_(2)) synthesized through a facile electrodeposition process and subsequent heat treatment.Based on electrochemical measurements,characterizations,and density functional theory calculations,a favorable“2+2”reaction mechanism with a two-step HER process and a two-step HzOR step was fully proved and the specific effect of P doping on HzOR kinetics was investigated.P/Fe-NiSe_(2) thus yields an impressive electrocatalytic performance,delivering a high current density of 100 mA cm^(−2) with potentials of−168 and 200 mV for HER and HzOR,respectively.Additionally,P/Fe-NiSe_(2) can work efficiently for hydrazine-assisted water electrolysis and Zn-Hydrazine(Zn-Hz)battery,making it promising for practical application.

Low-content Pt-triggered the optimized d-band center of Rh metallene for energy-saving hydrogen production coupled with hydrazine degradation

Utilizing the hydrazine-assisted water electrolysis for energy-efficient hydrogen production shows a promising application, which relies on the development and design of efficient bifunctional electrocatalysts. Herein, we reported a low-content Pt-doped Rh metallene(Pt-Rhene) for hydrazine-assisted water electrolysis towards energy-saving hydrogen(H_(2)) production, where the ultrathin metallene is constructed to provide enough favorable active sites for catalysis and improve atom utilization.Additionally, the synergistic effect between Rh and Pt can optimize the electronic structure of Rh for improving the intrinsic activity. Therefore, the required overpotential of Pt-Rhene is only 37 mV to reach a current density of-10 mA cm^(-2) in the hydrogen evolution reaction(HER), and the Pt-Rhene exhibits a required overpotential of only 11 mV to reach a current density of 10 mA cm^(-2) in the hydrazine oxidation reaction(HzOR). With the constructed HER-HzOR two-electrode system, the Pt-Rhene electrodes exhibit an extremely low voltage(0.06/0.19/0.28 V) to achieve current densities of 10/50/100 mA cm^(-2) for energy-saving H_(2) production, which greatly reduces the electrolysis energy consumption. Moreover,DFT calculations further demonstrate that the introduction of Pt modulates the electronic structure of Rh and optimizes the d-band center, thus enhancing the adsorption and desorption of reactant/intermediates in the electrocatalytic reaction.

Atomically Adjustable Rhodium Catalyst Synthesis with Outstanding Mass Activity via Surface-Li mi ted Cation Exchange

Rh has been widely studied as a catalyst for the promising hydrazine oxidation reaction that can replace oxygen evolution reactions for boosting hydrogen production from hydrazine-containing wastewater.Despite Rh being expensive,only a few studies have examined its electrocatalytic mass activity.Herein,surface-limited cation exchange and electrochemical activation processes are designed to remarkably enhance the mass activity of Rh.Rh atoms were readily replaced at the Ni sites on the surface of NiOOH electrodes by cation exchange,and the resulting RhOOH compounds were activated by the electrochemical reduction process.The cation exchange-derived Rh catalysts exhibited particle sizes not exceeding 2 nm without agglomeration,indicating a decrease in the number of inactive inner Rh atoms.Consequently,an improved mass activity of 30 A mg_(Rh)^(-1)was achieved at 0.4 V versus reversible hydrogen electrode.Furthermore,the two-electrode system employing the same CE-derived Rh electrodes achieved overall hydrazine splitting over 36 h at a stable low voltage.The proposed surface-limited CE process is an effective method for reducing inactive atoms of expensive noble metal catalysts.

Elucidating the electro-catalytic oxidation of hydrazine over carbon nanotube-based transition metal single atom catalysts

Elucidating the reaction mechanism of hydrazine oxidation reaction(HzOR)over carbon-based catalysts is highly propitious for the rational design of novel electrocatalysts for HzOR.In present work,isolated first-row transition metal atoms have been coordinated with N atoms on the graphite layers of carbon nanotubes via a M-N_(4)-C configuration(MSA/CNT,M=Fe,Co and Ni).The HzOR over the three single atom catalysts follows a predominant 4-electron reaction pathway to emit N_(2) and a negligible 1-electron pathway to emit trace of NH3,while their electrocatalytic activity for HzOR is dominated by the absorption energy of N2H4 on them.Furthermore,FeSA/CNT reverses the passivation effect on Fe/C and shows superior performance than CoSA/CNT and NiSA/CNT with a recorded high mass activity for HzOR due to the higher electronic charge of Fe over Co and Ni in the M-N_(4)-C configuration and the lowest absorption energy of N_(2)H_(4) on FeSA/CNT among the three MSA/CNT catalysts.

Multi-functional layered double hydroxides supported by nanoporous gold toward overall hydrazine splitting

Layered double hydroxides have demonstrated great potential for the oxygen evolution reaction,which is a crucial half-reaction of overall water splitting.However,it remains challenging to apply layered double hydroxides in other electrochemical reactions with high efficiency and stability.Herein,we report two-dimensional multifunctional layered double hydroxides derived from metalorganic framework sheet precursors supported by nanoporous gold with high porosity,which exhibit appealing performances toward oxygen/hydrogen evolution reactions,hydrazine oxidation reaction,and overall hydrazine splitting.The as-prepared catalyst only requires an overpotential of 233 mV to reach 10 mA·cm^(-2) toward oxygen evolution reaction.The overall hydrazine splitting cell only needs a cell voltage of 0.984 V to deliver 10 mA·cm^(-2),which is far more superior than that of the overall water splitting system(1.849 V).The appealing performances of the catalyst can be contributed to the synergistic effect between the metal components of the layered double hydroxides and the supporting effect of the nanoporous gold substrate,which could endow the sample with high surface area and excellent conductivity,resulting in superior activity and stability.

Hierarchical nano-on-micro copper with enhanced catalytic activity towards electro-oxidation of hydrazine

The electrochemical properties of catalyst materials are highly dependent on the materials structure and architecture. Herein, nano-on-micro Cu electrodes are fabricated by growing Cu microcrystals on Ni foam substrate, followed by introducing Cu nanocrystals onto the surface of the Cu microcrystals. The introduction of Cu nanocrystals onto the surface of Cu microcrystals is shown to dramatically increase the electrochemically active surface area and thus significantly enhances the catalytic activity of the catalyst electrode towards electro-oxidation of hydrazine. The onset potential （-1.04 V vs. AglAgCI） of the nano-on-micro Cu electrode is lower than those of the reported Cu-based catalysts under similar testing conditions, and a current density of 16 mA-cm-2, which is 2 times that of the microsized Cu electrode, is achieved at a potential of -0.95 V vs. Ag/AgCh Moreover, the nano-on-micro Cu electrode demonstrates good long-term stability.

Carbon black supported ultra-high loading silver nanoparticle catalyst for electro-oxidation and determination of hydrazine

Carbon black supported ultra-high loading silver nanoparticle catalyst (Ag/CB) was prepared by a modified ethylene glycol reduction method, using ethylene glycol as the reducing agent and sodium hydroxide as the pH adjusting agent. The X-ray diffraction, thermogravimetry and scanning electron microscopy characterizations showed that the Ag nanoparticles crystallized with a face-centered cubic structure and were densely stacked on the CB surface without aggregation, despite such a small average size (ca. 10 nm) and an ultra-high loading mass (392 wt.%). The electrochemical evaluation based on cyclic voltammetry, chronoamperometry and polarization tests revealed that the ultra-high loading Ag/CB catalyst possessed a superior electrocatalytic activity for the oxidation of hydrazine, via a diffusion-limited process and a 4-electron transfer pathway. Moreover, the chronoamperometry response on an electrode modified with this ultra-high loading Ag/CB catalyst exhibited a promising application for determination of hydrazine, due to a broad linear calibration ranging from 50 to 800 μM, a high sensitivity of 0.03795 A/ M and a low detection limit of 3.47 μM.

Magic hybrid structure as multifunctional electrocatalyst surpassing benchmark Pt/C enables practical hydrazine fuel cell integrated with energy-saving H_(2)production

A hybrid catalyst structure can provide abundant active sites and tailored electronic properties,but the major challenge lies in achieving delicate control over its composition and architecture to improve the catalytic activity toward different electrochemical reactions simultaneously.Herein,we present the rational design of a magic hybrid structure with low Pt loading(5.90 wt%),composed of CoPt_(3)and CoPt nanoparticles supported on N-doped carbon(CoPt_(3)/CoPt⊂PLNC).Importantly,it shows superior multifunctional catalytic activity in alkaline conditions,requiring a low overpotential of 341 and 20 mV to achieve 10 mA cm^(−2)for the hydrazine oxidation reaction(HzOR)/hydrogen evolution reaction(HER),respectively,and it delivers a half-wave potential of 0.847 V for the oxygen reduction reaction(ORR).Theoretical calculations reveal that the metal-carbon hybrid modulates kinetic behavior and induces electron redistribution,achieving the energetic requirements for multiple electrocatalysis.We demonstrate sustainable H_(2)production utilizing solely the CoPt_(3)/CoPt⊂PLNC catalyst,without external electric power input,suggesting its inspiring practical utility.

Coupling Co-Ni phosphides for energy-saving alkaline seawater splitting

The coupling of energy-saving small molecule conversion reactions and hydrogen evolution reaction(HER)in seawater electrolytes can reduce the energy consumption of seawater electrolysis and mitigate chlorine corrosion issues.However,the fabrication of efficient multifunctional catalysts for this promising technology is of great challenge.Herein,a heterostructured catalyst comprising CoP and Ni_(2)P on nickel foam(CoP/Ni_(2)P@NF)is reported for hydrazine oxidation(HzOR)-assisted alkaline seawater splitting.The coupling of CoP and Ni_(2)P optimizes the electronic structure of the active sites and endows excellent electrocatalytic performance for HzOR and HER.Impressively,the two-electrode HzOR-assisted alkaline seawater splitting(OHzS)cell based on the CoP/Ni_(2)P@NF required only 0.108 V to deliver 100 mA·cm^(−2),much lower than 1.695 V for alkaline seawater electrolysis cells.Moreover,the OHzS cell exhibits satisfactory stability over 48 h at a high current density of 500 mA·cm^(−2).Furthermore,the CoP/Ni_(2)P@NF heterostructured catalyst also efficiently catalyzed glucose oxidation,methanol oxidation,and urea oxidation in alkaline seawater electrolytes.This work paves a path for high-performance heterostructured catalyst preparation for energy-saving seawater electrolysis for H_(2) production.

一种用于肼氧化-复合海水电解制氢的富吡啶氮碳纸

丰富的中性海水有望替代高纯淡水用于绿氢制备,然而基于过渡金属材料催化的直接海水电解会因析氯反应(ClER)引发严重的腐蚀问题并造成二次重金属污染,且析氧反应(OER)的动力学缓慢.本工作中,我们报道了一种稳定的富吡啶氮的碳纸(N-CP-800),可以有效地催化肼氧化反应(HzOR),以取代中性海水中的OER用于节能制氢.结合电化学实验、原位衰减全反射-表面增强傅里叶变换红外光谱表征和密度泛函理论计算,我们发现:相较于吡咯氮和石墨氮,zig和arm构型的吡啶氮更有利于决速步(^(*)H+N_(2)H_(1))的质子脱附,以促进肼氧化反应.因此,N-CP-800在中性介质中进行HzOR时,仅需0.78 V(相对于可逆氢电势)便可达到10 mA cm^(-2),低于其OER/ClER竞争反应.当N-CP-800与非贵金属析氢催化剂CoP耦合进行HzOR-复合海水电解时,仅需1.56 V的电压即可达到10 mA cm^(-2),并能稳定运行200 h,优于Pt/C和RuO_(2)标准电极对催化的海水电解.

General synthesis of transition metal nitride arrays by ultrafast flash Joule heating within 500 ms

Transition metal nitrides(TMNs)are considered as viable alternatives to noble metal catalysts owing to their versatile electronic structure and favorable catalytic performance.However,the conventional synthetic processes for TMNs suffer from high energy consumption and low production yield.In this study,a range of TMNs and their hetero-composite arrays were successfully synthesized via an ultrafast flash Joule heating technology within 0.5 s.As a proof concept,the nitrides and hetero-composites were applied for the electrocatalytic hydrazine oxidation reaction(HzOR),in which the Co_(4)N/Mo_(16)N_(7)arrays shows the best performance with a geometric current density of 100 mA cm^(-2)at 23 mV(vs.reversible hydrogen electrode(RHE)).This work paves a new way for the ultrafast synthesis of TMNs which could meet the ever-increased energy crisis.

Regulating electronic structure of porous nickel nitride nanosheet arrays by cerium doping for energy-saving hydrogen production

Water electrolysis for energy-efficient H_(2)production coupled with hydrazine oxidation reaction(HzOR)is prevailing,while the sluggish electrocatalysts are strongly hindering its scalable application.Herein,we schemed a novel porous Ce-doped Ni3N nanosheet arrays grown on nickel foam(Ce-Ni3N/NF)as a remarkable bifunctional catalyst for both hydrogen evolution reaction and HzOR.Significantly,the overall hydrazine splitting system can achieve low cell voltages of 0.156 and 0.671 V at 10 and 400 mA·cm^(−2),and the system is remarkably stable to operate over 100 h continuous test at the high-current-density of 400 mA·cm^(−2).Various characterizations prove that the porous nanosheet arrays expose more active sites,and more excellent diffusion kinetics and lower charge-transfer resistance,therefore boosting catalytic performance.Furthermore,density functional theory calculation reveals that the incorporation of Ce can effectively optimize the free energy of hydrogen adsorption and promote intrinsic catalytic activity of Ni_(3)N.

Ru/NC heterointerfaces boost energy-efficient production of green H_(2)over a wide pH range

Green hydrogen(H_(2))is an import energy carrier due to the zero-carbon emission in the energy cycle.Nevertheless,green H_(2)production based on electrolyzer and photovoltaics(EZ/PV)remains limited due to the highly pH-dependant and energy exhausting overall water splitting.Herein,we report a series of Ru-nanocluster-modified mesoporous nanospheres(Rux@mONC)as pH-universal electrocatalysts towards both hydrogen evolution reaction(HER)and hydrazine oxidation reaction(HzOR).The optimal catalyst Ru_(2)0@mONC realizes remarkable catalytic activity and stability towards both HER and HzOR regardless of electrolytes.As a result,the electrode pair of Ru_(2)0@mONC//Ru_(2)0@mONC requires low cell-potentials of 39/429,405/926,and 164/1,141 mV to achieve the current density of 10/100 mA·cm^(−2),as well as the long-term stability for HzOR assisted electrochemical water splitting in alkaline,acidic,and neutral media,respectively.Those performances are more promising compared to the state-of-the-art electrocatalysts so far reported.A proof-of-concept test demonstrates an efficient production of green H_(2)powered by a single-junction silicon solar cell,which may inspire the use of a cost-effective EZ/PV system.Furthermore,a combined spectroscopic and theoretical study verifies the formation of abundant Ru/NC heterointerfaces in Ru_(2)0@mONC,which not only contributes to the balancing of H*adsorption/desorption in HER but also facilitates the*N_(2)H_(2)dehydrogenation in HzOR.

Preparation, Electrochemical Behavior and Electrocatalytic Activity of a Copper Hexacyanoferrate Modified Ceramic Carbon Electrode

A copper hexacyanoferrate modified ceramic carbon electrode （CuHCF/CCE） had been prepared by two-step sol-gel technique and characterized using electrochemical methods. The resulting modified electrode showed a pair of well-defined surface waves in the potential range of 0.40 to 1.0 V with the formal potential of 0.682 V （vs. SCE） in 0.050 mol·dm^-3 HOAc-NaOAc buffer containing 0.30 mol·dm^-3 KCl. The charge transfer coefficient （a） and charge transfer rate constant （ks） for the modified electrode were calculated. The electrocatalytic activity of this modified electrode to hydrazine was also investigated, and chronoamperometry was exploited to conveniently determine the diffusion coefficient （D） of hydrazine in solution and the catalytic rate constant （kcat）. Finally, hydrazine was determined with amperometry using the resulting modified electrode. The calibration plot for hydrazine determination was linear in 3.0 × 10^-6--7.5 × 10^-4 mol·dm^-3 with the detection limit of 8.0 × 10^-7 molodm^-3. This modified electrode had some advantages over the modified film electrodes constructed by the conventional methods, such as renewable surface, good long-term stability, excellent catalytic activity and short response time to hydrazine.