Hydrazine Electrooxidation Research Articles

Cover Feature: Self‐Supporting and Shell‐Core Pd−Ni@Ni Nanowire Arrays Electrode as Anode of Direct Carbohydrazide Fuel Cell (ChemElectroChem 6/2023)

The Cover Feature shows a direct carbohydrazide/hydrogen peroxide fuel cell equipped with a self-supporting and shell–core Pd–[email protected] nanowire arrays anode. In addition to the direct electrooxidation of carbohydrazide, the chemical decomposition of carbohydrazide into hydrazine and the subsequent hydrazine electrooxidation, and the chemical decomposition of hydrazine into hydrogen and the subsequent hydrogen electrooxidation, also occur on the Pd–Ni binary electrocatalyst. More information can be found in the Research Article by C. Peng et al.

An experimental and theoretical approach to electrochemical sensing of hydrazine at silver and copper hexacyanoferrates electrodes

This work evaluates the electrocatalytic oxidation of hydrazine (HDZ) by silver (AgHCF) and copper (CuHCF) hexacyanoferrates-modified glassy carbon electrodes kinetically and analytically through experimental electrochemistry and theoretical approaches. The materials were prepared by a two-step cyclic voltammetry (CV) routes and had their structural and morphological attributes attested by microscopic and spectroscopic characterization techniques. The AgHCF and CuHCF-modified electrodes showed quasi-reversible characteristics driven by K+ diffusion and adsorption processes, respectively. The kinetic properties of the materials towards HDZ electrooxidation were evaluated through CV and chronoamperometry techniques. The analyte exhibited irreversible electron transfer controlled by semi-infinite diffusion process for both Prussian blue analogs. The CuHCF-modified electrode showed superior diffusion coefficient (D = 2.17×10−5 cm2 s−1) and catalytic rate constant (kcat = 1.75×103 L mol−1 s−1) comparing to the silver analog (D = 2.31×10−6 cm2 s−1 and kcat = 8.06×102 L mol−1 s−1). The copper-based material also exhibited higher sensitivity (S) obtained through CV (S = 42 nA L µmol L−1) and batch injection analysis-coupled amperometry (BIA/amp) (S = 66.8 nA L µmol L−1) measurements, in comparison to AgHCF-modified electrode (S = 25 nA L µmol L−1 – CV; S = 22.3 nA L µmol L−1 – BIA/amp). Theoretical approaches showed that CuHCF material required lower energy (ΔEgap = 0.0397 eV) to promote an electron to the lowest unoccupied molecular orbital due to its cubic structural arrangement, justifying the better electrocatalytic results comparing to the hexagonal structure of the AgHCF material (ΔEgap = 0.0840 eV).

MoS2 Quantum Dot Modified Electrode: An Efficient Probe for Electrochemical Detection of Hydrazine

The development of an effective sensor system that can detect carcinogenic hydrazine is of prime scientific interest for the protection of human health and the environment. In the present study, MoS2 quantum dots (QDs) with an average diameter of ~5 nm were synthesized using a facile one-step, bottom-up hydrothermal method using cysteine as reducing as well as capping agents. The presence of cysteine was evaluated by FTIR spectroscopy. The synthesized MoS2 QDs were applied to modify the conventional glassy carbon electrode (GCE) in order to detect hydrazine electrochemically in neutral pH conditions. In the cyclic voltammetry (CV) study, the MoS2 QDs-modified electrode revealed much better catalytic activities for hydrazine electro-oxidation compared to the bare GCE surface. The smaller size of the QDs with high surface area and the presence of carboxylic acid containing cysteine on the surface of the QDs enhanced the adsorption as well as the electrocatalytic activity. The amperometric response of MoS2-QD-modified GCE unveiled excellent electrocatalytic sensing properties towards neurotoxic hydrazine with a very high sensitivity of 990 μAmM−1cm−2 (R2 = 0.998), low LOD of 34.8 μM, and a broad linear range. Moreover, this high-sensitive, binder and conducting filler-free MoS2-QD-based sensing system is very promising in agile amperometric detection of neurotoxic hydrazine for environmental monitoring in industrial sectors.

Alumina supported copper oxide nanoparticles (CuO/Al2O3) as high-performance electrocatalysts for hydrazine oxidation reaction

Direct hydrazine liquid fuel cell (DHFC) is perceived as effectual energy generating mean owing to high conversion efficiency and energy density. However, the development of well-designed, cost effective and high performance electrocatalysts is the paramount to establish DHFCs as efficient energy generating technology. Herein, gamma alumina supported copper oxide nanocatalysts (CuO/Al2O3) are synthesized via impregnation method and investigated for their electrocatalytic potential towards hydrazine oxidation reaction. CuO with different weight percentages i.e., 4%, 8%, 12%, 16% and 20% are impregnated on gamma alumina support. X-ray diffraction analysis revealed the cubic crystal structure and nanosized particles of the prepared metal oxides. Transmission electron microscopy also referred to the cubic morphology and nanoparticle formation. Electrochemical oxidation potential of the CuO/Al2O3 nanoparticles is explored via cyclic voltammetry as the analytical tool. Optimization of conditions and electrocatalytic studies shown that 16% CuO/Al2O3 presented the best electronic properties towards N2H2 oxidation reaction. BET analysis ascertained the high surface area (131.2546 m2 g1) and large pore diameter (0.279605 cm³ g−1) for 16% CuO/Al2O3. Nanoparticle formation, high porosity and enlarged surface area of the proposed catalysts resulted in significant oxidation current output (600 μA), high current density (8.2 mA cm−2) and low charge transfer resistance (3.7 kΩ). Electrooxidation of hydrazine on such an affordable and novel electrocatalyst opens a gateway to further explore the metal oxide impregnated alumina materials for different electrochemical applications.

First principles of hydrazine electrooxidation at oxide-free and oxide-based palladium electrodes in complex media.

In this study, fundamental aspects that have impact on the electroanalytical detection of hydrazine in phosphate, acetate and yeast fermentation medium in an analytically significant concentration range by several types of palladium (Pd)-modified electrodes, namely, Pd-ink, Pd-sputtered films and palladium nanoparticles (Pd-NPs) were systematically studied. The efficiency of hydrazine electrooxidation is not affected by the composition of multicomponent medium (i), presence of oxygen (ii), morphology or electroactive area (iii), but more likely depends on the purity degree of the electrode surface from residual palladium oxides (iv). In addition, using advanced methods of nanoanalytics and quantum chemistry, the crucial role of hydrazine surface adsorption (v) on oxide-free and oxide-based Pd-electrodes is highlighted. The obtained knowledge will provide future development strategies of electrodes based on nanoparticles of noble metals for tuned and efficient hydrazine electrooxidation in complex fermentation media.

Trapezohedral platinum nanocrystals with high-index facets for high-performance hydrazine electrooxidation

Direct hydrazine fuel cell is a promising portable energy conversion device due to its high energy density and free of carbon emissions. To realize the practical applications, the design of highly efficient electrocatalysts for hydrazine oxidation reaction (HzOR) is crucial. Metal nanocrystals with high-index facets have abundant step sites with reactivity. In this study, we prepared trapezohedral Pt nanocrystals (TPH Pt NCs) enclosed by {311} high-index facets and investigated the catalytic performance for hydrazine oxidation. TPH Pt NCs possess a specific activity of 39.1 mA·cm-2 at 0.20 V, much higher than {111}-faceted octahedral (13.9 mA·cm-2) and {100}-faceted cubic Pt NCs (9.11 mA·cm-2). Meanwhile, TPH Pt NCs also show superior stability. Density functional theory (DFT) calculation indicates that Pt(311) facilitates the deprotonation of N2H4* to N2H3* (the rate-determining step) and improves the HzOR activity. This study is helpful for the design of advanced electrocatalysts for HzOR, especially high-index faceted Pt nanocatalysts.

An amorphous/nanocrystalline NixP/Ni heterojunction for electrooxidation of hydrazine

a-NixP/Ni/NF exhibits exceptionally high activity towards alkaline HzOR, excellent stability and a nearly 100% selectivity for four-electron hydrazine electrooxidation.

Hydrazine High-Performance Oxidation and Sensing Using a Copper Oxide Nanosheet Electrocatalyst Prepared via a Foam-Surfactant Dual Template.

This work demonstrates hydrazine electro-oxidation and sensing using an ultrathin copper oxide nanosheet (CuO-NS) architecture prepared via a versatile foam-surfactant dual template (FSDT) approach. CuO-NS was synthesised by chemical deposition of the hexagonal surfactant Brij®58 liquid crystal template containing dissolved copper ions using hydrogen foam that was concurrently generated by a sodium borohydride reducing agent. The physical characterisations of the CuO-NS showed the formation of a two-dimensional (2D) ultrathin nanosheet architecture of crystalline CuO with a specific surface area of ~39 m2/g. The electrochemical CuO-NS oxidation and sensing performance for hydrazine oxidation revealed that the CuO nanosheets had a superior oxidation performance compared with bare-CuO, and the reported state-of-the-art catalysts had a high hydrazine sensitivity of 1.47 mA/cm2 mM, a low detection limit of 15 μM (S/N = 3), and a linear concentration range of up to 45 mM. Moreover, CuO-NS shows considerable potential for the practical use of hydrazine detection in tap and bottled water samples with a good recovery achieved. Furthermore, the foam-surfactant dual template (FSDT) one-pot synthesis approach could be used to produce a wide range of nanomaterials with various compositions and nanoarchitectures at ambient conditions for boosting the electrochemical catalytic reactions.

Promoting Effect of Cu on Pd Applied to the Hydrazine Electro-Oxidation and Direct Hydrazine Fuel Cells

Use of liquid fuels in fuel cells is advantageous due to the easier and safer handling, transportation, and storage. Among the different options, hydrazine is of interest since the formation of highly poisoning carbonaceous species is avoided, in addition to its high energy density. In the search for more active direct hydrazine fuel cells (DHFC), this study analyzes the influence of Cu as an auxiliary metal on Pd. Three different PdxCu/C (x = 3, 1, and 0.33) catalysts were prepared by chemical reduction with NaBH4. The materials were physiochemically characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Electrochemical analysis in a three-electrode glass cell and a single-cell DHFC was also carried out to study the impact on the electroactivity. Cu exerts a beneficial effect by reducing the adsorption energies of the adsorbed species and donating oxidized species for the completion of the hydrazine electro-oxidation, optimally balanced in the Pd1Cu/C (maximum power density of 180 mW cm−2). As a counterpoint, Cu slightly promotes the non-faradaic decomposition of hydrazine, seen by a larger H2 signal in mass spectroscopy in the anode exhaust at high current densities, which results in a slight loss in faradaic efficiency.

Interface Engineering of SRu-mC3N4 Heterostructures for Enhanced Electrochemical Hydrazine Oxidation Reactions

Hydrazine oxidation in single-atom catalysts (SACs) could exploit the efficiency of metal atom utilization, which is a substitution for noble metal-based electrolysers that results in reduced overall cost. A well-established ruthenium single atom over mesoporous carbon nitride (SRu-mC3N4) catalyst is explored for the electro-oxidation of hydrazine as one of the model reactions for direct fuel cell reactions. The electrochemical activity observed with linear sweep voltammetry (LSV) confirmed that SRu-mC3N4 shows an ultra-low onset potential of 0.88 V vs. RHE, and with a current density of 10 mA/cm2 the observed potential was 1.19 V vs. RHE, compared with mesoporous carbon nitride (mC3N4) (1.77 V vs. RHE). Electrochemical impedance spectroscopy (EIS) and chronoamperometry (i-t) studies on SRu-mC3N4 show a smaller charge-transfer resistance (RCt) of 2950 Ω and long-term potential, as well as current stability of 50 h and 20 mA/cm2, respectively. Herein, an efficient and enhanced activity toward HzOR was demonstrated on SRu-mC3N4 from its synergistic platform over highly porous C3N4, possessing large and independent active sites, and improving the subsequent large-scale reaction.

Nanocoral Architecture for Enhanced Hydrazine Assisted Water Oxidation: Insight from Experiment and Theory

• Hydrothermally synthesized nanocoral copper-cobalt sulfide showed HzOR at lower potential of 0.2 V in KOH. • Oxygen evolution at near thermodynamic voltage. • Hydrazine assists the oxygen evolution reaction (OER) due to the involvement of hydroxyl ions in KOH medium. • DFT and PDOS studies revealed higher electrochemical activity for copper-cobalt sulfide than cobalt sulfide. • Redox interaction of Co and Cu ions in copper-cobalt sulfide. Hydrothermally synthesized nanocoral structures of copper-cobalt sulfide is identified as a novel catalyst for electrocatalytic splitting of hydrazine (N 2 H 4 ) in both basic and neutral mediums. Electrochemical studies in basic medium indicated that electrocatalytic splitting of hydrazine occurs at a much lower potential 0.2 V (vs Ag/AgCl) in copper-cobalt sulfide in comparison to cobalt sulfide. Gaseous analysis reveals formation of oxygen at near thermodynamic voltage of 1.23 V. Experimental observations revealed the influence of hydrazine electro-oxidation on water splitting reaction. Adsorption energy of N 2 H 4 on catalyst surface and projected density of states from computational studies using Density Function Theory (DFT) proved higher activity for copper-cobalt sulfide catalyst for the electrocatalytic splitting of Hydrazine. Plausible mechanism is depicted based upon the experimental observations.

Catalytic electro-oxidation of hydrazine by thymol based-modified glassy carbon electrode

In the present, thymol based new organic compounds (4A, 4B and 4C) are designed and synthesized via Steglich Esterification Reactions and Pd-catalyst Sonogashira Coupling Reactions. After isolation and characterization, thymol based hybrid molecules are used for hydrazine (N2H4) electrooxidation reactions as anode catalysts. A variety of metal based anode catalyst have been reported in literature, but this study may be the first study for thymole based hybrid molecules as an anode catalyst in fuel cells. The performance of hybrid molecules was investigated via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in hydrazine solution. Hybrid 2-isopropyl-5-methylphenyl-4-oxo-4-(5-(p-tolylethynyl)thiophen-2-yl)butanoate (4C) gives the highest performance as 3.66 mAcm−2 (17.24 mAmg−1). Our results displayed that natural products like thymol derivatives may be new generation anode catalyst for fuel cells, and they may be alternative for expensive Pd and Pt based metal anode catalyst.

Synthesis of porous cobalt oxide nanosheets: highly sensitive sensors for the detection of hydrazine

A highly sensitive, reliable, and reproducible sensor for detecting hydrazine was fabricated using a porous cobalt oxide (Co2O3) nanosheets electrode. The Caffeine assisted Co2O3 nanosheets were prepared by a low-temperature aqueous chemical growth method. The morphology, phase purity, and porosity of Co2O3 nanosheets were examined via SEM, XRD, and BET techniques. SEM results reveal the hexagonal sheet-like morphology of synthesized Co2O3 nanosheets, while the XRD technique illustrates high phase purity. Furthermore, the BET technique demonstrated the increased surface area exhibited by the newly synthesized Co2O3 nanomaterial. The hydrazine sensor based on the Co3O4 nanosheet electrode demonstrated relatively high sensitivity (1.632 μA cm−2 μM−1) and a rather low detection limit (0.05 μM) due to the fast electro-oxidation of hydrazine catalyzed by Co3O4 nanosheets. The unique porous structure of Co3O4 nanosheets offers a promising probe candidate for efficient electrochemical sensors of hydrazine.

Highly active bifunctional electrocatalyst: Nanoporous (Ni,Co) 0. 85 Se anchored on rGO for water and hydrazine oxidation

It is an effective strategy to decrease water splitting overpotential by designing high-performance oxygen evolution reaction (OER) electrocatalyst or substituting OER by hydrazine electrooxidation (HzOR). Herein, we fabricated bifunctional (Ni,Co)0.85Se/rGO with nanoporous structure via electrodeposition towards HzOR and OER. In comparison with (Ni,Co)0.85Se and NF, superior electrocatalytic activity and stability towards HzOR and OER were observed for (Ni,Co)0.85Se/rGO. The synergistic effects of (Ni,Co)0.85Se with rGO, high electrochemical surface area (ECSA), high electrical conductivity and the rapid release rate of bubbles from electrode surface induced by its superaerophobic result in superior performance of (Ni,Co)0.85Se/rGO. The OER process requires a low overpotential of 247 mV at 10 mA cm−2, and a high durability of 86.1% during 48 h long-term test at 10 mA cm−2. When changing OER with HzOR, HzOR process can generate a high current density of 211 mA cm−2 at a potential of 0.2 V vs RHE, and a high stability of 92.3% after 24 h test at a high current density of 50 mA cm−2. This study displays a versatile, cost-effective and industrial strategy to produce highly active catalysts for bifunctional application.

Carbon nanotube supported Ga@PdAgCo anode catalysts for hydrazine electrooxidation in alkaline media

In this study, carbon nanotube supported (CNT) monometallic (Pd), trimetallic (PdAgCo), and multimetallic (Ga@PdAgCo) catalysts in different weight percentages (0.5–10%) are synthesized by the NaBH4 reduction method and characterized transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-mass spectrometry (ICP-MS), and X-ray diffraction (XRD) analytical methods. According to the TEM analysis results, while agglomeration doesn’t observe for 3% Ga@PdAgCo(80:10:10)/CNT catalyst, agglomeration is observed in certain parts for 7% Ga@PdAgCo(80:10:10)/CNT catalyst. The occurrence of agglomeration has a negative effect on catalytic activity. XRD analysis shows that as metal was added, the diffraction peaks are negatively shifted, thereby forming an alloy. Electrochemical measurements such as cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) are used for the hydrazine electrooxidation activities of the catalysts. The highest specific activity is achieved as 250.39 mA/cm2 (22592.66 mA/mg Pd) with catalyst. The electrochemical surface area (ECSA) of 3% Ga@PdAgCo/CNT catalysts is also calculated as 1392.43 m2/g. The homogeneous distribution of the metals on the support material and the alloy formation has an effect on the catalytic activity for the 3% Ga@PdAgCo(80:10:10)/CNT catalyst. Although Pd is an active metal on its own, the synergistic effect between them as a result of the formation of alloys with different metals and the electronic state change on the catalyst by adding different metals to Pd has a great influence on the catalytic activity. As a result, Ga@PdAgCo/CNT catalyst with its high current value stands out as a new anode catalyst for hydrazine electrooxidation.

Smartphone-Based Electrochemiluminescence for Visual Simultaneous Detection of RASSF1A and SLC5A8 Tumor Suppressor Gene Methylation in Thyroid Cancer Patient Plasma.

Visual one-step simultaneous detection of low-abundance methylation is a crucial challenge in early cancer diagnosis in a simple manner. Through the design of a closed split bipolar electrochemistry system (BE), detection of promoter methylation of tumor suppressor genes in papillary thyroid cancer, RASSF1A and SLC5A8, was achieved using electrochemiluminescence. For this purpose, electrochemiluminescence of luminol loaded into the Fe3O4@UiO-66 and gold nanorod-functionalized graphite-like carbon nitride nanosheet (AuNRs@C3N4 NS), separately, on the anodic and cathodic pole bipolar electrodes (BPEs) in two different chambers of a bipolar cell were recorded on a smartphone camera. To provide the same electric potential (ΔEelec) through the BPEs to conduct simultaneous light emission, as well as to achieve higher sensitivity, anodic and cathodic poles BPEs were separately connected to ruthenium nanoparticles electrodeposited on nitrogen-doped graphene-coated Cu foam (fCu/N-GN/RuNPs) to provide a hydrogen evolution reaction (HER) and polycatechol-modified reduced graphene oxide/pencil graphite electrode (PC-rGO/PGE) to provide electrooxidation of hydrazine. Moreover, taking advantages of the strong cathodic ECL activity due to the roles of AuNRs, as well as the high density of capture probes on the UiO-66 and Fe3O4 roles in improving the signal-to-background ratio (S/B) in complicated plasma media, a sensitive visual ECL immunosensor was developed to detect two different genes as model target analytes in patient plasma samples. The ability of discrimination of methylation levels as low as 0.01% and above 90% clinical sensitivity in thyroid cancer patient plasma implies that the present strategy is able to diagnose cancer early, as well as monitor responses of patients to therapeutic agents.

Synthesis of Novel Artemisinin Derivatives and Their Electrochemical Properties

AbstractIn present, new artemisinin‐based organic compounds (1–6) are designed and synthesized in excellent yields (up to 97 %) via Steglich Esterification reactions. All new artemisinin derivatives are tested as anode catalysts for hydrazine electrooxidation reactions with electrochemical methods in 1 M KOH/0.5 M N2H4 solution. Hybrid molecule 1 exhibits the best catalytic activity in hydrazine electrooxidation reaction with 2.28 mA cm−2 value. Moreover, response surface methodology (RSM) is applied to investigate of optimum electrode conditions. By using optimum conditions, hydrazine electrooxidation is obtained as 3.55324 mA cm−2. As a result, artemisinin‐based hybrid compounds may be alternative, and next‐generation anode catalyst for direct hydrazine fuel cells.

Ruthenium and palladium oxide promoted zinc oxide nanoparticles: Efficient electrocatalysts for hydrazine oxidation reaction

Development of highly catalyzing electrode materials for hydrazine electrooxidation reaction (HzOR) demands a judicious assortment of intrinsically active candidates, precise engineering of electrodes for enhancement of active sites and building of electronically conductive structures. Herein, we report the novel, innovative and robust heterogeneous electrocatalysts for HzOR for ultimate hydrogen generation and their applicability in direct hydrazine fuel cell (DHFC). The presented catalysts comprised of ZnO microparticles supported on γ-Al2O3 with different weight percentages (10, 20, 30, 40 wt/wt%). Binary catalyst i.e. 20% ZnO/Al2O3 displayed the maximum catalytic output towards HzOR, so it is chosen to further combine with RuO2 and PdO to investigate a promoted and enhanced oxidation output. Ternary metal oxide catalysts i.e. RuO2-ZnO/Al2O3 and PdO-ZnO/Al2O3 with varied contents of RuO2 and PdO (0.1, 0.5 and 1 wt/wt%) are prepared via co-impregnation method. X-Ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy coupled energy dispersive spectroscopy (SEM-EDS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are the techniques employed for physio-chemical characterization of samples. Among all the investigated catalysts, 1% PdO-ZnO/Al2O3 produced the most catalyzing behavior toward HzOR owing to its largest diffusion coefficient (50.0 × 10−6 cm2 s−1), highest current density (5.2 mA cm−2) and high ECSA (0.23 cm2). The catalysts showed sufficient reproducibility and stability by scanning multiple cycles and testing similar electrodes after different time intervals. This is the first study of hydrazine electrooxidation protocol employing RuO2 and PdO promoted γ-alumina supported ZnO structured electrocatalysts.

Rational design of FeS2 microspheres as high-performance catalyst for electrooxidation of hydrazine

• Hydrazine is one of the raw materials of direct fuel cells, which play an important role in the field of energy, the electrocatalysis of hydrazine oxidation is an important challenge,but most electrocatalysts still suffer from low efficiency and stability. • Inspired by the relatively recognized performance of transition metal sulfides in the oxidation of hydrazine oxidation, the catalytic properties of two relatively stable iron sulfides of FeS 2 and Fe 3 S 4 were firstly investigated and compared via the density functional theory (DFT) calculations. Therein, the Fe centres were identified as the catalytic sites of all possible active locations. • Due to the different coordination numbers of iron-sulfur, the free energies of the dehydrogenation steps on FeS 2 were far less than those on Fe 3 S 4 , which led to the much better catalytic performance of FeS 2 . Accordingly, FeS 2 and Fe 3 S 4 were then prepared by a facile one-step hydrothermal strategy. • Following experimental results were in agreement with the DFT calculation ones: FeS 2 microspheres exhibited promising electrocatalytic performance in the electrocatalytic decomposition of hydrazine with a starting potential of 0.22 V vs . reversible hydrogen electrode (RHE) and peak oxidation current of 16 mA cm −2 (0.5 V vs. RHE). Meanwhile, stability and high faradaic efficiency (3.5e − /N 2 H 4 ) were obtained for hydrazine oxidation to N 2 . Inspired by the relatively recognized performance of transition metal sulfides in the oxidation of hydrazine, the catalytic properties of FeS 2 and Fe 3 S 4 are compared via the density functional theory calculations. Due to the different coordination numbers of iron-sulfur, the free energies of the dehydrogenation steps on FeS 2 are far less than those on Fe 3 S 4 , which led to the much better catalytic performance of FeS 2 . Accordingly, FeS 2 microspheres are rationally proposed as a more efficient electrocatalyst for hydrazine oxidation, which is then prepared by a facile one-step hydrothermal strategy. Such FeS 2 microspheres show great activity for hydrazine oxidation with an onset oxidation potential of 0.22 V vs . reversible hydrogen electrode, and a peak current density of 16 mA cm −2 . Meanwhile, stability and high faradaic efficiency (3.5e − /N 2 H 4 ) is obtained for hydrazine oxidation to N 2 .

Hierarchically nanostructured Ni2Fe2N as an efficient electrocatalyst for hydrazine oxidation reaction

A Ni foam-supported, hierarchically nanostructured Ni 2 Fe 2 N nanoflowers (Ni 2 Fe 2 N/NF) exhibits high activity and good operation stability towards hydrazine electrooxidation. • Hierarchically nanostructured Ni 2 Fe 2 N was anchored on Ni foam by a two-step procedure. • Ni 2 Fe 2 N/NF exhibits higher HzOR activity than the top-notch electrocatalysts hitherto reported. • Ni 2 Fe 2 N/NF shows high reaction selectivity toward faradic decomposition of hydrazine. The application of direct hydrazine fuel cells (DHFCs) as portable or vehicular power sources calls for the development of cheap and efficient catalysts for the anodic hydrazine oxidation reaction (HzOR). Herein, we report the facile fabrication of a Ni-foam-supported, hierarchically nanostructured Ni 2 Fe 2 N (Ni 2 Fe 2 N/NF) as a high-performance HzOR catalyst. The Ni 2 Fe 2 N/NF catalyst was fabricated by a simple hydrothermal method and a subsequent nitridation treatment. The thus-prepared Ni 2 Fe 2 N possesses high intrinsic activity towards HzOR, good electronic conductivity as well as a hierarchical architecture, which endows the catalyst with abundant active sites and improved mass transfer properties. Benefiting from these attributes, Ni 2 Fe 2 N/NF demonstrates highly efficient HzOR performance with a high current density of 1017 mA cm −2 at 0.3 V versus RHE, excellent stability and a nearly 100% selectivity for the faradaic hydrazine decomposition following 4-electron pathway, surpassing most previously reported top-notch HzOR electrocatalysts.