Hexamethylenetetramine Research Articles

DMAP and HMTA manganese(III) meso-tetraphenylporphyrin-based coordination complexes: Syntheses, physicochemical properties, structural and biological activities

The reactions of the (triflato)(meso-tetra(para-methoxyphenyl)porphyrinato)manganese(III) ([MnIII(TMPP)(SO3CF3)] complex with an excess of 4-dimethylaminopyridine (DMAP) and hexamethylenetetramine (HMTA) have been examined. These reactions yield crystalline [MnIII(TMPP)(DMAP)2](0.1Cl)(0.9SO3CF3)•2CHCl3 (I) and [MnIII(TMPP)(HMTA)2](SO3CF3)•2CH2Cl2 (II) complexes, respectively. The hyper d-type electronic spectra of I-II are characteristic for high-spin (S = 2) Mn(III) metalloporphyrins with very redshifted Soret bands. A cyclic voltammetry investigation was carried out on these two Mn(III) coordination compounds. The crystal structures of the solid complexes I-II were determined by X-ray single-crystal diffraction and elucidated by Hirshfeld surface approach. Furthermore, bioactivity of the H2TMPP free base, the [MnIII(TMPP)(SO3CF3)] starting material and complexes I-II, was assessed by a set of in vitro tests checking for antioxidant, antibacterial and antifungal (against several strains) effects.

Methenamine hippurate to prevent recurrent urinary tract infections in older women: protocol for a randomised, placebo-controlled trial (ImpresU)

IntroductionMethenamine hippurate is a urinary antiseptic used as preventive treatment for recurrent urinary tract infections (UTIs) in some Scandinavian countries. However, the scientific evidence for the preventive effect and safety...

Novel porous perovskite composite CeO2@LaMnO3/3DOM SiO2 as an effective catalyst for activation of PMS toward oxidation of urotropine

• Novel composite perovskite was successfully prepared. • The novel catalyst has high PMS activation and URO removal efficiency. • The three components in it showed a synergetic effect. Perovskites with stable crystal structure and excellent catalytic performance have attracted extensive attention in peroxomonosulfate (PMS) activation, however, severe agglomeration has always been the main obstacle limiting the catalytic activity of them, so novel perovskite catalysts are urgently needed. In this study, three-dimensional ordered macroporous silica (3DOM SiO 2 ) was prepared by colloidal crystal template method, then CeO 2 @LaMnO 3 /3DOM SiO 2 was prepared by sol-gel method combined with impregnation method and used to activate PMS for urotropine (URO) degradation. CeO 2 @LaMnO 3 /3DOM SiO 2 activated PMS system exhibited high URO removal efficiency and quick kinetic, as 99.98 % URO was degraded even within 30 min. The catalyst has a wide pH range and still has high catalytic activity in the presence of organic matter and inorganic ions. The three components in CeO 2 @LaMnO 3 /3DOM SiO 2 showed a synergetic effect. CeO 2 and LaMnO 3 were uniformly loaded on 3DOM SiO 2 , which effectively avoided agglomeration. The specific surface area of CeO 2 @LaMnO 3 /3DOM SiO 2 was 11.88 times that of LaMnO 3 prepared by sol-gel method. There are two redox cycles of Ce 3+ /Ce 4+ and Mn 2+ /Mn 3+ /Mn 4+ in CeO 2 and LaMnO 3 , respectively, which synergistically realize the activation of PMS. Both quenching experiments and electron paramagnetic resonance (EPR) analysis revealed that that SO 4 − , OH and 1 O 2 jointly achieved the degradation of URO. In summary, CeO 2 @LaMnO 3 /3DOM SiO 2 would be a promising candidate for practical wastewater treatment.

Methenamine as prophylaxis for recurrent urinary tract infections: an overview of the ALTAR trial

Current recommended treatment for recurrent uncomplicated urinary tract infections in women includes low-dose daily antibiotics. The UK Antimicrobial Resistance Strategy document underlines the importance of non-antibiotic preventive treatments for common infections such as UTIs. The ALTAR trial investigated the clinical effectiveness of one such non-antibiotic treatment, the urinary antiseptic Methenamine Hippurate in the context of a randomised, open-label, pragmatic, two-arm non-inferiority trial with the comparator of daily low-dose antibiotics. Non-inferiority was confirmed in this study and the authors recommend that it should now be considered as a first-line preventive treatment for recurrent uncomplicated urinary tract infections in women.

Ionometric sensor for express determination of hexamethylenetetramine

The article is devoted to the development of an ionometric sensor for the determination of hexamethylenetetramine (HMTA). It was found that poorly soluble complex compounds with the composition (HMTA)3(PMo12O40)2 and (HMTA)3(PW12O40)2 are formed as a result of the interaction of the cation of the test substance with the anions of heteropoly acids. The obtained compounds were used as electrode active substances for polyvinyl chloride membranes of ionometric sensors. Phthalic acid derivatives (dibutyl and dioctyl phthalates) were used as solvents for plasticized membranes. The optimal composition of the membranes was established. The dependences of the electrochemical properties of the obtained sensor membranes on various factors were studied. This made it possible to choose the optimal conditions for the operation of the ionometric sensor. The response time of the sensor does not exceed 3 minutes, and the service life of the membrane (about 40 days) allows performing determination without replacement. The detection limit of hexamethylenetetramine using this sensor is 1.010–5 mol/l, and quantitative determination can be carried out in a fairly short time (5–10 min).

HMTA-assisted synthesis of praseodymium oxide nanostructures integrated multiwalled carbon nanotubes for efficient levofloxacin electrochemical sensing

In this study, two-dimensional (2D) flake-like praseodymium oxide (Pr6O11) nanostructures were synthesized via a hexamethylenetetramine (HMTA)-assisted hydrothermal method. The sonochemical technique is used to prepare the Pr6O11 integrated multiwalled carbon nanotubes (MWCNTs) for the detection of levofloxacin (LFN). The physical properties of the Pr6O11/MWCNT were examined by X-ray diffractometer (XRD), X-ray photoelectron microscope (XPS), Raman, Fourier-transform infrared (FT-IR) spectroscopy, and field-emission scanning electron microscope. The glassy carbon electrode (GCE) surface was modified using the flake-like Pr6O11 and non-covalently integrated MWCNTs. Significantly, the fabricated electrode shows good electrocatalytic activity, more active sites, a large specific surface area, and excellent conductivity. The studied electro-oxidation mechanism of LFN at the Pr6O11/MWCNT modified electrode/electrolyte interface is two electrons and two proton transfer process. Owing to the synergistic effect, the Pr6O11/MWCNT modified electrode exhibits a long linear concentration range of 0.499–684 μM, appreciable detection limit (LOD) of 5.3 nM (3 × S/b), and high sensitivity of 7.97 μA/μM/cm2 toward LFN detection. Besides, the Pr6O11/MWCNT-modified electrode shows the good anti-interfering property, reproducibility, repeatability, and storage stability. Satisfactory recovery results were calculated for the detection of LFN in human urine, serum, and river water samples.

Rational design of MOFs-derived Co-Ru species embedded N-doped carbon/carbon matrix for highly-efficient and multifunctional electrocatalysis

Developing efficient and durable multifunctional electrocatalysts for HER, OER and ORR is a pressing challenge for the practical application of water splitting and regenerative Zn-air batteries. Herein, core–shell Co-Ru nanocomposites embedded in N-doped carbon matrix (CoRu@NC) is fabricated for highly active HER by using hexamethylenetetramine (HMT) based MOFs as precursor, which is further developed into bimetallic oxide encapsulated into carbon (CoRuOx@C) as multifunctional catalysts for OER and ORR. Taking advantage of synergistic effects between two species and the porous core–shell structure, the resulting water electrolyzer (CoRu@NC||CoRuOx@C) displays excellent performance in pH-universal electrolyte, surpassing Pt/C||RuO2 counterpart and most reported electrocatalysts. More attractively, the CoRuOx@C exhibites significantly high-activity for ORR in 0.1 M KOH, possessing a half-wave potential of 0.864 V (23 mV higher than that of Pt/C benchmark) with excellent durability. This work provides a feasible strategy to construct multifunctional catalysts for efficient water splitting and Zn-air batteries.

Investigation of hexamethylenetetramine effects on formation and corrosion resistance of anodic coatings developed on AZ31B alloys

To fabricate calcium-phosphate (CaP) coatings with good corrosion resistance on AZ31B alloys via micro-arc oxidation (MAO) treatment, hexamethylenetetramine (HMTA) was selected as an effective MAO additive of magnesium alloys. The influences of HMTA concentrations on formation mechanism and coating property were systematically investigated in a near-neutral base solution composed of NH4HF2, EDTA-CaNa2, phytic acid and phosphoric acid. The results show that HMTA can increase the solubility of calcium salts and significantly promote the formation of MAO coatings on AZ31B alloys. In a base solution with 360 g/L HMTA, the fabricated MAO sample achieves the best corrosion resistance in Hank's solution and the corrosion current density (icorr) is significantly decreased by two orders of magnitude than that treated in solution without HMTA. During MAO treatment, acting as an effective corrosion inhibitor of magnesium alloys, HMTA is helpful for coating formation via protecting the magnesium sample from corrosion. In 3.5 % NaCl solution with different HMTA concentrations, the maximum inhibition efficiency is 94.57 % at a HMTA concentration of 360 g/L. Moreover, HMTA molecules are absorbed on the surface of AZ31B alloys following the Langmuir absorption isotherm in the range of 120 to 360 g/L, however, excessively high concentrations fail to conform with the equation, which may be attributed to steric hindrance.

Facile synthesis of zinc hydroxyfluoride nanobelt and effect of hexamethylenetetramine for growth direction

ABSTRACT Control of nanomaterial morphology has been investigated to utilize for the desired application. 1D nanomaterials are ideal for various applications because of their excellent carrier transportability and huge specific surface area. Due to their advantages, various methods have been developed to grow in a specific direction. Herein, we introduced a simple synthesis method of freestanding Zinc hydroxidefluoride (ZnOHF) nanobelt as 1D material without seed or substrate using aqueous solutions. The ZnOHF nanobelt was synthesized using zinc fluoride and hexamethylenetetramine (HMT) at 80°C for 3 h. Even though low synthesis temperature, ZnOHF demonstrated good crystallinity and a homogeneous nanobelt structure. The ZnOHF nanobelts were grown over several μm to <010> direction with less than 100 nm width. In addition, the growth direction of the nanobelt was controlled by the concentration of HMT. The width of the nanobelt was broader by a decrease in HMT concentration. It was considered that crystal nucleation and growth of ZnOHF could be influenced by OH− and NH4 + ions generated from HMT decomposition.

Enhanced energy storage performance of surfactant assisted grown cobalt hydroxide

The use of surfactant during synthesis process is critical in determining morphology as well as properties of nanomaterials. In this line, this work reports surfactant assisted synthesis of Co(OH)2 nanomaterials and their characterizations for energy storage applications. Cobalt hydroxide nanoparticles are synthesized using chemical co-precipitation method at 80 °C using hexamethylenetetramine (HMTA) as surfactant. The sample prepared using surfactant and without surfactant are labelled as CHHMTA and CH, respectively. Scanning electron microscopy, X-ray diffraction, and FTIR techniques were used to evaluate the structural, morphological, and elemental features of the produced products. To understand the energy storage capabilities of the collected products, cyclic voltammetry (CV) and galvanometric charge/discharge (GCD) are used. In comparison to bare Co(OH)2 nanoparticles, HMTA coated particles exhibits improved charge storage characteristics. The specific capacitance for CH and CHHMTA was determined as 127 and 344 Fg−1 at 1 Ag−1 current density, respectively.

Prophylactic Antimicrobial Prescribing in Australian Residential Aged-Care Facilities: Improvement is Required.

Inappropriate antimicrobial use can lead to adverse consequences, including antimicrobial resistance. The objective of our study was to describe patterns of prophylactic antimicrobial prescribing in Australian residential aged-care facilities and thereby provide insight into antimicrobial stewardship strategies that might be required. Annual point prevalence data submitted by participating residential aged-care facilities as part of the Aged Care National Antimicrobial Prescribing Survey between 2016 and 2020 were extracted. All antimicrobials except anti-virals were counted; methenamine hippurate was classified as an antibacterial agent. The overall prevalence of residents prescribed one or more prophylactic antimicrobial on the survey day was 3.7% (n = 4643, 95% confidence interval 3.6-3.8). Of all prescribed antimicrobials (n = 15,831), 27.1% (n = 4871) were for prophylactic use. Of these prophylactic antimicrobials, 87.8% were anti-bacterials and 11.4% antifungals; most frequently, cefalexin (28.7%), methenamine hippurate (20.1%) and clotrimazole (8.8%). When compared with prescribing of all antimicrobial agents, prophylactic antimicrobials were less commonly prescribed for pro re nata administration (7.0% vs 20.3%) and more commonly prescribed greater than 6 months (52.9% vs 34.1%). The indication and review or stop date was less frequently documented (67.5% vs 73.8% and 20.9% vs 40.7%, respectively). The most common body system for which a prophylactic antimicrobial was prescribed was the urinary tract (54.3%). Of all urinary tract indications (n = 2575), about two thirds (n = 1681, 65.3%) were for cystitis and 10.6% were for asymptomatic bacteriuria. Our results clearly identified immediate antimicrobial stewardship strategies that aim to improve prophylactic antimicrobial prescribing in Australian residential-aged care facilities are required.

Structural, Morphological and Optical Properties of Zinc Oxide Nanorods prepared by ZnO seed layer Annealed at Different Oxidation Temperature

In this work, zinc oxide (ZnO) nanorods structure in the form of thin film have been grown on soda-lime glass (SLG) substrate incorporating two simple steps. Firstly, ZnO seed layer was pre-deposited onto the SLG substrate by the thermal evaporation method. During this process, the oxidation temperatures were varied in the range of 450 oC to 650 oC annealed for 3 hours. Then, the nanorods structure were grown on the surface of the seed layer by sol-gel immersion method with the use of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and hexamethylenetetramine (HMT) in deionized (DI) water. The optical, structural and morphological properties at different oxidation temperatures were studied using UV-Vis-NIR spectroscopy, X-ray diffraction (XRD) and Field-enhanced Scanning Electron Microscopy (FeSEM). The surface morphology results revealed the formation of hexagonal shaped ZnO on top of the seed layer as a result of heterogeneous nucleation. X-ray diffraction results show that the c-axis orientation became more prominent while the optical band gap of ZnO thin films decreases from 3.31 eV to 3.14 eV as the annealing temperature increased respectively. It is shown that the size and alignment of ZnO NRs are greatly affected by the pre-deposition annealed temperature of the ZnO seed layer on the surface of SLG substrate.

Structural, dielectric, magnetic, and ferroelectric properties of bismuth ferrite (BiFeO3) synthesized by a solvothermal process using hexamethylenetetramine (HMTA) as precipitating agent

Multiferroic BiFeO3 (BFO) has been synthesized by the solvothermal technique for 4 h at 180 °C using Hexamethylenetetramine (HMTA) as a precipitating agent. Optimizations on HMTA concentration were performed to attain BFO in a narrow possible time using the solvothermal method. The effect of HMTA concentration on structural properties was investigated by XRD, FE-SEM, FT-IR, and Raman techniques. Moreover, the magnetic, ferroelectric, dielectric, and optical properties were studied by VSM, Ferroelectric analyser, Dielectric spectrometer, and UV–Vis–NIR spectrometer, respectively. The XRD data has unveiled the significant role of HMTA, as a precipitating agent, in obtaining the pure phase BFO at a particular concentration. A high concentration of HMTA (6 M) is found to be more favourable for producing pure phase BFO within the short reaction time of 4 h without any impurity phase formations. The FE-SEM images have shown the formation of granular structures that are inhomogeneously distributed throughout the powdered BFO with porosities. In addition, the magnetic measurements confirmed that the BFO synthesized with varying HMTA concentration exhibits a reasonable week ferromagnetic behaviour. However, the pure BFO powder synthesized at 6 M HMTA shows high magnetization value (0.72 emu/g) compared to the other samples synthesized at low concentrations of HMTA. Further, the dielectric measurements of all the synthesized BFO samples have shown a decrease in dielectric loss with an increase in frequency. Whereas the dielectric behaviour exhibited by the pure BFO synthesized at 6 M HMTA has shown a high dielectric constant value with moderate dielectric loss. A ferroelectric analyser studies the ferroelectric behaviour of BFO powder. The study revealed that pure phase BFO synthesized with 6 M HMTA exhibits a high value of remanent polarization with unsaturated P-E loops due to the high leakage current in the sample. The UV–Vis data shows that the BFO samples exhibited an excellent optical absorption in the visible range with narrow optical band gaps. Therefore, all the characterizations related to magnetic, structural, dielectric, ferroelectric, and optical properties of synthesized pure BFO have proven the significance of precipitating agent HMTA in the solvothermal synthesis method. Based on our findings, the synthesized pure phase BFO can be an excellent semiconducting photocatalyst for multiferroic based photocatalysis applications.

Experimental study of the hydroquinone (HQ)–hexamethylenetetramine (HMTA) gel system for conformance improvement in extremely high‐temperature reservoirs

An organically crosslinked polymer with hydroquinone (HQ)–hexamethylenetetramine (HMTA) as crosslinker used for profile control was analyzed systematically at extremely high temperatures (over 150°C). The optimal gelation time and gelation performance may be achieved by changing the polymer and crosslinking agent concentrations. The gelation time is decreased and the gelation performance is improved as the concentration of polymer and hydroquinone-HMTA increased. It still has a very dense microscopic three-dimensional network structure after 3 months of aging at 150°C. The gel system can effectively improve the formation profile by plugging the high permeability layer and introducing subsequent water into the undisturbed layer.

Synthesis, structural characterization, and Hirshfeld surface analysis of novel NLO active 1-methyl-1,3,5,7-tetraazaadamantan-1-ium 3-carboxy-5-nitrobenzoate hydrate

Single crystals of 1-methyl-1,3,5,7-tetraazaadamantan-1-ium 3-carboxy-5-nitrobenzoate hydrate (I) were grown from an aqueous solution containing hexamethylenetetramine (HMT) and 5-nitroisophthalic acid (5NIPA) by slow evaporation solution growth technique after the mild hydrothermal process. The crystal structure is elucidated by single-crystal X-ray diffraction analysis. It crystallizes in the monoclinic system with acentric space group Cc. The cation and anion present in the adduct are bridged by a water molecule, which is interconnected with CH···O and OH···O hydrogen bonds. The relative second harmonic generation (SHG) efficiency measurements characterized by the Kurtz powder technique reveal that (I) is an active SHG material. The grown crystals were further characterized by FT-IR, UV-DRS, and photoluminescence spectral analysis. Theoretical calculations were performed using density functional theory to derive the dipole moment, polarizability, and first-order molecular hyperpolarizability (β). The intermolecular hydrogen bonding interactions are analysed by Hirshfeld surface analysis and fingerprint plots. Theoretically estimated high β rationalized by the experiment. The molecular electrostatic potential (MEP) maps and Mulliken atomic charge were calculated using density functional theory (DFT) calculations.

Hydrothermal in situ synthesis of high-crystallinity layered double hydroxide on electrospun polyacrylonitrile non-woven membrane: Application as anion capture filter

Layered double hydroxide (LDH) crystals were grown in the presence of polyacrylonitrile (PAN) nanofibers to develop a three-dimensionally-structured hybrid filter with high anion adsorption performance. The tensile strength and chemical resistance of the PAN nanofibers manufactured by electrospinning were improved upon heat treatment at 250 °C for 60 min. The growth of LDH on PAN was conducted by hydrolysis using urea or hexamethylenetetramine (HMT), and optimum conditions for this “in situ synthesis” were investigated. As a result, LDH plate-like crystals with a lateral size of ~20 μm were obtained by hydrothermal treatment at 140 °C for 24 h using HMT. The crystals grew densely perpendicular to the surface of the PAN fibers. After converting the LDH grown on the fiber fabric to LDH contain Cl− in the interlayer, the resulting fabric was set in a filter holder and a phosphoric acid adsorption test was conducted. The results showed that the hybrid filter prepared by this in situ hydrothermal synthesis had good phosphate adsorption characteristics, and that small amounts of phosphate ions were adsorbed selectively from water containing competing sulfate ions.

Fabrication of polyamide thin-film nanocomposite reverse osmosis membrane with improved permeability and antibacterial performances using silver immobilized hollow polymer nanospheres

Thin-film nanocomposite (TFN) membrane with polyamide (PA) layer containing nanofillers have attracted extensive attention due to their excellent properties. In this study, hollow polymer phenolic resin nanospheres (HPS) and silver nanoparticles immobilized HPS (Ag/HPS) were synthesized with 2,4-dihydroxy benzoic acid and hexamethylene tetramine, and used as nanofillers to prepare TFN-HPS and TFN-Ag/HPS membrane. In this paper, the effects of HPS and Ag/HPS addition (0.002 wt%, 0.004 wt%, 0.006 wt%, 0.008 wt% and 0.010 wt%) on TFN membranes separation performance were investigated. The results showed that the water fluxes of TFN-HPS and TFN-Ag/HPS membranes reaches 64.7 L·m−2·h−1 and 64.0 L·m−2·h−1, respectively, when the addition amount of HPS and Ag/HPS was 0.006 wt%, which is about 80 % higher than that of TFC membranes (36.0 L·m−2·h−1). Furthermore, the TFN-HPS and TFN-Ag/HPS membrane have excellent long-term stability. After seven days of continuous operation, the water flux of TFN-HPS and TFN-Ag/HPS membranes remains at 50.0 L·m−2·h−1 and 45.6 L·m−2·h−1, respectively. In addition, the fouling resistance of TFN-HPS and TFN-Ag/HPS membranes is significantly improved, with flux recovery rates reaching 88.8 % and 91.4 %, respectively. Importantly, the sterilization rate of TFN-Ag/HPS membrane containing antibacterial silver to Escherichia coli is up to 96.7 %.

Physicochemical Studies on the Effect of Hexamine Addition and Ratio on the Properties of Acrylonitrile Butadiene Rubber Composites

AbstractThe effect of hexamine (HA) addition on the morphological, thermal, mechanical, and dielectric properties of acrylonitrile butadiene rubber (NBR) composites has been considered. In this regard, HA was composited with NBR in different part percentages. The prepared formulations were characterized by using ATR‐FTIR and mapped with AFM for their topographical features which revealed multiple protrusions and showed that HA was distributed in the form of clustered crystals on the rubber surface and within the rubber matrix. The investigated data revealed that the tensile strength, elongation, and shore A hardness were improved with addition and increasing HA ratio till 50 phr then reneged. The thermal gravimetric analysis (TGA) showed a graduated decreasing effect on the thermal stability by addition of HA. Moreover, upon increasing the proportion of HA in the composite, the electrical resistivity was dropped by several orders of magnitude at a critical filler concentration. The conductivity through composite material is described as a transport mechanism that involves electrons tunneling through the gaps founded in between of the two discontinuous conducting elements and a continuous conducting network forming. Experimental and calculated values of electrical resistivity showed close similarity only at higher HA loading ratios.

Methenamine Hippurate With Cranberry Capsules Versus Cranberry Alone for Urinary Tract Infection Prevention in a Short-Term Indwelling Foley Catheter Population After Urogynecologic Surgery: A Double-Blinded Randomized Controlled Trial

(Abstracted from Female Pelvic Med Reconstr Surg 2022;28:e55–e61) Urinary tract infections (UTIs) after pelvic reconstructive surgery (PRS) can result in high rates of readmission, morbidity, and mortality. The prevalence of UTI ranges from 10% to 76%, and postoperative urinary retention due to catheterization can occur in up to 43% in this population.

Hexamethylenetetramine-derived pyridinic N abundant porous carbon-supported Co/Co-Nx nanoparticles as highly efficient oxygen reduction catalyst and zinc-air battery cathode

Fuel cells and metal-air batteries attracted extensive research attention owing to high power density, renewability, and environmental friendliness. Hence, developing heteroatom-doped pyridinic N abundant porous carbon materials with large surface area have an extensive effect on oxygen reduction reaction (ORR) for fuel cell and metal-air battery. Herein, high content of pyridinic N porous carbon-supported Co/Co-Nx nanoparticles were synthesized as ORR catalysts by carbonizing complexes of hexamethylenetetramine (HMT) and Co(NO3)2·6H2O with silica template. The HMT-Co@SiO2-900 with high content of pyridinic N, large specific surface area, and porous structure exhibits a more positive half-wave potential (0.85 V) than 20% Pt/C and the outstanding performance oxygen evolution reaction behavior. The low Tafel slope of HMT-Co@SiO2-900 revealed the faster reaction kinetics during ORR. The HMT-Co@SiO2-900 zinc-air battery showed a high excellent cyclic stability in continuous charge/discharge cycles for 420 times at 10 mA/cm2. This research provides an efficient strategy for the preparation of pyridinic N porous electrocatalyst by the reduction of diffusion restriction and exposure of active sites.