Phytic acid-assisted fabrication of superhydrophilic Ru 3D electrode for electrocatalytic hydrogenation of p-Nitrophenol

A superhydrophilic Ru-based 3D electrode, denoted as Ru-PA/NF, was fabricated under the assistance of phytic acid (PA) for electrocatalytic hydrogenation of p-Nitrophenol. PA serves as a multifunctional modulator to facilitate the dispersion of active Ru species in porous nickel foam (NF), meanwhile enhance the surface wettability as well as adjust the micromorphology. In alkaline media, the Ru-PA/NF electrode shows the PNP conversion of 94.68% and the PAP selectivity of 99% after 9 h, accompanied by the faraday efficiency (FE) of 73.15%. Over the superhydrophilic Ru-PA/NF the rate constant of PNP conversion into PAP is 2.62-times higher than that over the hydrophobic Ru/NF prepared without the aid of PA, and FE of Ru-PA/NF is 1.28-times higher than Ru/NF. This can be ascribed to intriguing features of Ru-PA/NF involving higher Ru loading, more exposed sites, superior electrolyte wetting along with faster charge transfer rate.     

Fe(III) grafted MoO3 nanorods for effective electrocatalytic fixation of atmospheric N2 to NH3

Electrocatalytic nitrogen reduction reaction (ENRR) offers a carbon-neutral process to fix nitrogen into ammonia, but its feasibility depends on the development of highly efficient electrocatalysts. Herein, we report that Fe ion grafted on MoO₃ nanorods synthesized by an impregnation technique can efficiently enhance the electron harvesting ability and the selectivity of H⁺ during the NRR process in neutral electrolyte. In 0.1 M Na₂SO₄ solution, the electrocatalyst exhibited a remarkable NRR activity with an NH₃ yield of 9.66 μg h^?1 mg^?1_cat and a Faradaic efficiency (FE) of 13.1%, far outperforming the ungrafted MnO₃. Density functional theory calculations revealed that the Fe sites are major activation centers along the alternating pathway.     

Electrodeposited NiMoP catalysts on carbon felt for hydrogenation of indigo during electrocatalytically splitting water

Electrochemical hydrogenation is an environmentally favorable alternative to chemical reduction of indigo because it performs under ambient conditions using water as the donor of hydrogen. The purpose of this work is to fabricate electrocatalysts with high activity and durability for electrocatalytic hydrogenation of indigo. This work compares the performances of a series of Ni based catalysts (Ni, NiMo, NiP and NiMoP) on the substrate of carbon felt (CF) for electrolyzing water. Both the overpotential and Tafel slop are decreased as a function of the components as Ni > NiMo > NiP > NiMoP. Hence, NiMoP/CF shows the excellent performance based on the thermodynamics (η₁₀ = 239 mV) and kinetics (Tafel slope = 89.7 mV·dec^?1) for splitting water. Further, the electrode of NiMoP/CF was used for the electrocatalytic hydrogenation of indigo. The conversion efficiency and Faradic efficiency can be improved as 26.2% and 10.7% respectively. Furthermore, the dyeing behavior of the electrohydrogenated indigo is similar to that of conventional reduction methods. Thus, the present work offers foundational results and paves the way for the design of new catalytic materials for the reduction of vat dyes.     

Platinum nanoparticles decorated on graphitic carbon nitride-ZIF-67 composite support: An electrocatalyst for the oxidation of butanol in fuel cell applications

In the present study, we report an eco-friendly and simple route to design and synthesize novel nanocomposite catalyst based on platinum nanoparticles anchored on binary support of graphitic carbon nitride (g-C₃N₄) and cobalt-metal-organic framework (ZIF-67). For this purpose, ZIF-67 was prepared by precipitation method and g-C₃N₄ was prepared through thermal polymerization method. Later, ZIF-67 and g-C₃N₄ were hybridized through sonication to get homogeneous g–C₃N₄–ZIF-67 nanocomposite support material. Platinum nanoparticles (PtNPs) were uniformly deposited on g–C₃N₄–ZIF-67 by an electrochemical method. The as-developed nanocatalyst was characterized by morphological, structural and electrochemical techniques. The electrocatalytic activity of PtNPs@g–C₃N₄–ZIF-67 nanocatalyst towards butanol oxidation was evaluated via CV, CA, LSV and EIS in an alkaline medium. Results revealed that the proposed catalyst showed greatly enhanced electrooxidation of butanol in terms of high magnificent current density, lower oxidation potential, excellent long-term stability, large surface area, low charge transfer resistance and less toxic ability. Enhanced catalytic performance of the proposed catalyst could be ascribed to the synergistic effect of g–C₃N₄–ZIF-67 nanocomposite and PtNPs. The PtNPs@g–C₃N₄–ZIF-67 catalyst holds promising potential applications to be used as an anodic electrocatalyst for the development of high-performance alkaline fuel cells.     

Se doped nickel-molybdenum bimetal sulfide with enhanced electrochemical activity for hydrogen evolution reaction

In this work, we synthesized Se doped MoS₂@Ni₃S₂ with nanosheets coated nanorods structure supported on Ni foam (MoNiSeS). Firstly, MoS₂@Ni₃S₂ (MoNiS) nanorods was synthesized by hydrothermal method. After selenization treatment, MoSe₂ successfully formed on the edge of MoS₂ nanosheets and particle Ni₃S₂ transformed into NiSe, in which MoSe₂ and NiSe acted as new phase in MoNiSeS. The obtained MoNiSeS only needs a low overpotential of 68 mV to reach the current density of 10 mA cm^?2, and has a low Tafel plots of 72.77 mV dec^?1 and good electrochemical durability, whose electrochemical activity is much better than that of MoNiS and NiSeS, implying the introduction of Mo and Se is beneficial to improve the electrocatalytic performance of NiS for HER. In addition, the proper amount of Mo source, which has an effect on the morphology of product, has also been investigated. For MoNiSeS, the typical nanosheets coated nanarods expose more active sites and the synergic effects is good to the improvement of the catalytic activity. Meanwhile, WNiSeS has also been prepared using the same method and the corresponding results show that the electrochemical activity of WNiSeS is much better than that of NiSeS, proving the universality of this strategy.     

Electrocatalytic activity for the hydrogen evolution of the electrodeposited Co–Ni–Mo,Co–Ni and Co–Mo alloy coatings

The electrocatalytic activity for the HER of the ternary Co–Ni–Mo and the binary Co–Ni and Co–Mo alloy coatings is investigated in 1 M KOH solution. The surface morphology and the structure of the studied coatings is characterized by SEM and XRD analysis. The electrocatalytic activity for the HER is evaluated using cyclic voltammetry, electrochemical impedance spectroscopy, cathodic polarization and chronopotentiometry techniques. XRD analysis reveals that all studied coatings are composed of the Co hcp structure. However, alloy deposits with Mo is characterized by more nanocrystalline structure. Electrochemical experiments reveal superior electrocatalytic activity of coatings with Mo in comparison to Co–Ni alloy. This is the results of larger real surface area of Co–Mo and Co–Ni–Mo alloys, which is confirmed by the higher surface roughness factors (R_f) calculated based on the EIS results. The ternary alloy coating is characterized by the highest R_f parameter and the highest catalytic activity for the HER.     

Electrochemical analysis and convection-enhanced mass transfer synergistic effect of MnOx/Ti membrane electrode for alcohol oxidation

The different electrocatalytic reactors could be constructed for the electrocatalytic oxidation of 2,2,3,3-tetrafluoro-1-propanol(TFP) with two typical MnO_x/Ti electrodes, i.e.the electrocatalytic membrane reactor(ECMR) with the Ti membrane electrode and the electrocatalytic reactor(ECR) with the traditional Ti plate electrode.For the electro-oxidation of TFP, the conversion with membrane electrode(70.1%) in the ECMR was 3.3 and 1.7 times higher than that of the membrane electrode without permeate flow(40.8%) in the ECMR and the plate electrode(21.5%) in the ECR, respectively.Obviously, the pore structure of membrane and convection-enhanced mass transfer in the ECMR dramatically improved the catalytic activity towards the electro-oxidation of TFP.The specific surface area of porous electrode was 2.22 m~2·g~(-1).The surface area of plate electrode was 2.26 cm~2(1.13 cm~2× 2).In addition, the electrochemical results showed that the mass diffusion coefficient of the MnO_x/Ti membrane electrode(1.80 × 10~(-6) cm~2·s~(-1)) could be increased to 6.87 × 10~(-6) cm~2·s~(-1) at the certain flow rate with pump, confirming the lower resistance of mass transfer due to the convection-enhanced mass transfer during the operation of the ECMR.Hence, the porous structure and convection-enhanced mass transfer would improve the electrochemical property of the membrane electrode and the catalytic performance of the ECMR,which could give guideline for the design and application of the porous electrode and electrochemical reactor.     

Facile synthesis of Ni doped CoWO4 nanoarrays grown on nickel foam substrates for efficient urea oxidation

Urea electrolysis is a promising technology for hydrogen production, which can alleviate environmental pollution of urea-rich wastewater. It's worth noting that electrochemistry activity can be significantly improved by reasonably regulating the electron configuration around the active site for the doped materials. In this work, a series of well-tuned Ni doped CoWO₄ nanoarrays on Ni foam supports have been prepared through a typical hydrothermal approach for the first time. Moreover, the resulting Ni–CoWO₄-2 material significantly promotes urea oxidation performance with an applied potential of 1.35 V at 50 mA cm^?2, which is lower than that of water oxidation reaction (1.60 V). Density functional theory results suggest that the Ni doped CoWO₄ has larger urea adsorption energy compared with CoWO₄ and the CO(NH₂)₂ molecule is strongly adsorbed on surface of Ni doped CoWO₄, which is beneficial to accelerate the kinetics of the reaction and improve the electrocatalytic activity of the urea electrolysis.     

Hydrogen evolution reaction activity and stability of sintered porous Ni-Cu-Ti-La2O3 cathodes in a wide pH range

Finding a low-cost, efficient, stable, and workable electrode for the production of hydrogen based on the hydrogen evolution reaction (HER) is particularly critical. At present, the use of Pt/C electrodes is under development, but the expensive cost hinders its wide application in the HER field. Herein, a novel porous Ni-Cu-Ti-La₂O₃ cathode with a porosity of 29.07% was proved to be an excellent substitute for the HER, which was fabricated by vacuum sintering based on powder metallurgy. The hydrogen evolution efficiency is superior to that of commercial 20% Pt/C under pH = 14.1 condition (2.67 mol/L KOH). The HER activity is also close to commercial 20% Pt/C under pH = 0.1 (1 mol/L HCl) and pH = 8.1 (3.34% simulated seawater) conditions and exceeds it after reaching a high potential. Meanwhile, it can achieve good HER stability within 48 h and maintain its HER activity after 1000 continuous cycle electrolysis.     

MOF-derived cobalt manganese phosphide as highly efficient electrocatalysts for hydrogen evolution reaction

Hydrogen is considered as a viable alternative to traditional fossil fuels. Hydrogen evolution reaction (HER) by electrochemical water splitting is the most reliable and effective way for the sustainable production of pure hydrogen. The design and synthesis of highly active and stable non-noble-metal-based electrocatalysts is the core of the large-scale application of this technology. Herein, peony petal-like CoMnP/NF nanomaterials growing on nickel foam (NF) are prepared via facile hydrothermal and phosphorization methods. The results showed that CoMnP/NF had excellent HER activity in acidic and alkaline media. In 0.5 M H₂SO₄, CoMnP/NF only needed 66.6 mV overpotential to drive the current density of 10 mA cm^?2, with a Tafel slope of 38.8 mV dec^?1. In addition, a particularly low overpotential of 53.9 mV and Tafel slope of 63 mV dec^?1 are required to achieve the same current density in the 1 M KOH electrolyte. Meanwhile, the electrocatalyst showed good stability after 1000 cyclic voltammetry tests and 12 h I-T tests. In the 1 M KOH electrolyte, the current density of 10 mA cm^?2 achieved with only 1.70 V battery voltage, and the electrocatalyst showed excellent stability. The performance of CoMnP/NF can be attributed to the synergistic effect between Co and Mn atoms and the high electrochemical surface area (ECSA). This study provides a valuable strategy for the synthesis of non-precious metals and high-performance catalytic materials.