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.

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.

Cobalt‐regulation‐induced dual active sites in Ni_(2)P for hydrazine electrooxidation

Better understanding of electrochemical reaction behaviors of hydrazine electrooxidation at metal phosphides has long been desired and the optimization of reaction kinetics has been proved to be operable.Herein,the dehydrogenation kinetics of hydrazine electrooxidation at Ni_(2)P is adjusted by Co as the(Ni_(0.6)Co_(0.4))_(2)P catalyzes HzOR effectively with onset potential of–45 mV and only 113 mV is needed to drive the current density of 50 mA cm^(‒2),showing over 60 mV lower than Ni_(2)P and Co_(2)P.It also delivers the maximum power density of 263.0 mW cm^(-2) for direct hydrazine fuel cell.Detailed experimental results revealed that Co doping not only decreases the adsorption energy of N_(2)H_(4) on Ni sites,lowering the energy barrier for dehydrogenation,but also acts as the active sites in the optimal reaction coordination to boost the reaction kinetics.This work represents a breakthrough in improving the catalytic performance of non‐precious metal electrocatalysts for hydrazine electrooxidation and highlights an energy‐saving electrochemical hydrogen production method.

Ligand-free monophasic CuPd alloys endow boosted reaction kinetics toward energy-efficient hydrogen fuel production paired with hydrazine oxidation

Optimizing the structure and components is a prevalent strategy for increasing electrocatalytic energy-saving H 2 fuel production.One of the sustainable and efficient techniques is electrocatalytic water split-ting for H 2 generation,but it is still restricted by the kinetically sluggish OER.Due to the lower standard oxidation potential of−0.33 V,replacing the OER with anodic hydrazine oxidation reaction(HzOR)is an effective way to extensively reduce the use of electricity in water electrolysis.Through alloying,the semiconductor and adsorption characteristics of Cu,interlaced by Pd 2+solution on the Pd surface by pulsed laser ablation(PLA)in methanol,are selectively altered to maximize cathodic HER and anodic HzOR performance.The optimal Cu1Pd3/C ratio demonstrates outstanding HER performance with a low overpotential of 0.315 V at 10 mA cm^(−2),as well as an ultralow overpotential of 0.560 V for HzOR in 0.5 M N_(2) H_(4)/1.0 M KOH.Furthermore,the constructed HzOR-assisted electrolyzer cell with Cu1Pd3/C||Cu1Pd3/C as anode and cathode exhibits a cell voltage of 0.505 V at 10 mA cm^(−2) with exceptional en-durance over 5 h.The current study advances competent CuPd alloys as multifunctional electrocatalysts for H 2 fuel production using a HzOR-assisted energy-efficient electrolyzer.

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.

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.

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.

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.

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.