Reaction In Acid Medium Research Articles

Three-Dimensional Needle Branch-like PANI/CoNiP Hybrid Electrocatalysts for Hydrogen Evolution Reaction in Acid Media

In this work, a kind of three-dimensional (3D) needle branch-like array nanostructured PANI/CoNiP hybrid electrode self-supported on nickle foam (NF) is explored. This 3D needle branch-like array n...

FeNi-functionalized 3D N, P doped graphene foam as a noble metal-free bifunctional electrocatalyst for direct methanol fuel cells

Designing high-performance bifunctional electrocatalysts for oxygen reduction (ORR) and methanol oxidation (MOR) reaction is essential for the wide application of direct methanol fuel cells. Here, we have prepared a novel three-dimensional (3D) FeNi-functionalized N, P doped graphene foam (FeNi@NP-GF) by a simple and cost-effective one-step pyrolysis method, as excellent bifunctional electrocatalyst for direct methanol fuel cells. Compared with metal-free and transition metal single-doped graphene foam catalysts (NP-GF, Fe@NP-GF and Ni@NP-GF), the resulting FeNi@NP-GF catalyst showed more positive half-wave potential and higher limiting current density in ORR reaction. Furthermore, it manifests a four-electron transfer process and strong methanol crossover resistance in the alkaline medium. The above results ascribed to the synergistic effect of Fe/Ni-Nx species formed with Fe/Ni and N species and multiple active sites in the 3D porous graphene material. Moreover, FeNi@NP-GF acted as good support for Pt nanoparticles (NPs). Pt/FeNi@NP-GF catalyst displayed remarkable catalytic performance and high stability for methanol electrooxidation reaction in acid medium.

Synthesis of metal and non-metal doping hematite nanoparticles for adsorption and photocatalytic degradation of acid red 14 in aqueous solutions

ABSTRACT Adsorption and photocatalytic decolourisation of AR14 in aqueous solution was investigated using α-Fe2O3, α-Fe2O3/S and α-Fe2O3/CdS in dark and under UV irradiation, respectively. The synthesis of alpha iron oxide nanoparticles and combining heteroatoms in its matrix were performed by a simple co-precipitation method. Samples were characterised by XRD, Raman and pHPZC. The dye adsorption on the catalysts’ surfaces showed a strong dependence on the pH, and the adsorption played the main role in the photocatalytic reaction in acidic medium. The pseudo first order kinetic model was found to be the best fit for the adsorption of AR14 by the three catalysts (R2 > 0.99) and is in good agreement with a chemisorption mechanism. The plot of intra-particle diffusion model showed a three-stage adsorption process which suggests that more than one process affects the AR14 adsorption. α-Fe2O3/S and α-Fe2O3/CdS nanoparticles had significant enhancement on the decolourisation of AR14 compared to the bulk material. A rate removal of 78%, 94% and 98% of the AR14 was recorded at pH = 3 under UV irradiation for α-Fe2O3, α-Fe2O3/S and α-Fe2O3/CdS respectively. The decolourisation was strongly enhanced in the presence of H2O2 leading to Fenton-like process. Added H2O2 competes with AR14 for the powder surface sites and reduces its adsorption on the catalysts’ surfaces. The addition of propanol-2 as a radical scavenger confirms that •OH radicals are the main species responsible for the decolourisation of AR14 inα-Fe2O3/H2O2 system. Fenton-like process provides more selective oxidation for AR14 that have a higher affinity for the iron oxide surface and also for the modified iron oxide surface.

Rh2P Activity at a Fraction of the Cost? Co2–xRhxP Nanoparticles as Electrocatalysts for the Hydrogen Evolution Reaction in Acidic Media

The composition-dependent hydrogen evolution reaction (HER) activity of Co2–xRhxP nanoparticles in acid is reported. The motivation for the current study stems from (1) prior work demonstrating tha...

Hetero Atom Doped Graphene Nanoarchitectonics as Electrocatalysts Towards the Oxygen Reduction and Evolution Reactions in Acidic Medium

Oxygen electrocatalysis plays a vital role in sustainable energy solutions concerning the storage and conversion using electrical energy into chemical energy and vice versa. The important processes in oxygen electrocatalysis includes oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) remain clean affordable efficient and economically feasible solutions. Carbon based metal-free materials owing to their abundance, electrical conductivity, porosity, structural modification at the molecular levels and exceptional stability under harsh conditions are emerging as advanced electrodes toward the design of high-performance oxygen electrocatalysts. This review provides a critical overview of this rapidly developing field including the design of efficient hetero atom doped graphene-based metal-free catalysts, defect engineering and co-doping with special emphasis on the electrochemical activity in acidic media. The latest trends in the design of hetero atom doped graphene nanoarchitectonics for ORR and OER along with important electrochemical parameters in the field were also outlined. Furthermore, the design of efficient and robust bi-functional hetero atom doped graphenes elucidating structure-property relationship toward multifunctional OER/ORR behaviour was highlighted. The key challenges and future opportunities in this exciting field are profoundly discussed.

Metal- and Nonmetal-Incorporated Vitamin B <sub>12</sub> on Graphene as a Bioderived Electrocatalyst for High-Performance Oxygen Reduction Reaction in Acidic Media

Metal- and Nonmetal-Incorporated Vitamin B <sub>12</sub> on Graphene as a Bioderived Electrocatalyst for High-Performance Oxygen Reduction Reaction in Acidic Media

Multimetallic nanostructures for electrocatalytic oxygen evolution reaction in acidic media

In this review, the authors highlighted the recent progress on the noble metal-based multimetallic electrocatalysts toward the oxygen evolution reaction under acidic condition.

One-step fabrication of CuO-doped TiO2 nanotubes enhanced the catalytic activity of Pt nanoparticles towards the methanol oxidation reaction in acid media

To meet the requirements for the potential applications of fuel cells, it is of vital importance to search for advanced electrocatalysts toward the methanol oxidation reaction that have both high electrocatalytic activity and great CO resistance.

Atomically dispersed Pd catalysts promote the oxygen evolution reaction in acidic media

A Pd-doped Pt3Sn-based single atom alloy catalyst (Pd-Pt3Sn) was synthesized via a hydrothermal method. The overpotential of Pd-Pt3Sn is lower than that of commercial Pd/C and IrO2 catalysts at 10 mA cm-2. This is due to the synergistic effect between Pt, Sn and Pd and the influence of electronic effects on their catalytic performance.

Dealloyed RuNiOx as a robust electrocatalyst for the oxygen evolution reaction in acidic media.

We report here the dealloying treatment on a RuNiOx catalyst for enhanced acidic oxygen evolution reaction (OER) performance. Specifically, the dealloyed RuNiOx is capable of delivering a current density of 50 mA cm-2 at a low overpotential of 280 mV and demonstrates superior stability after 10 000 potential cycles.

Shape-selective rhodium nano-huddles on DNA for high efficiency hydrogen evolution reaction in acidic medium

Cost-effective Rh NPs have been synthesized over a DNA scaffold which acts as an effective electrocatalyst for HER in acidic medium. DNA stabilized Rh NPs during synthesis and also acts as a stable binder with minimum loading for electrocatalysis.

Ni@Carbon Nanotubes Derived from Ni-MOF as a Superior Electrocatalyst for Hydrogen Evolution Reaction in Acidic Medium

Hydrogen production through an electrochemical process is a challenging task to realize the renewable energy based technologies such as fuel cells. Herein, we developed a simple, scalable reflux me...

Gettering La Effect from La3IrO7 as a Highly Efficient Electrocatalyst for Oxygen Evolution Reaction in Acid Media

AbstractDeveloping highly active, durable, and cost‐effective electrocatalysts for the oxygen evolution reaction (OER) is of prime importance in proton exchange membrane (PEM) water electrolysis techniques. Herein, a surface lanthanum‐deficient (SLD) iridium oxide as a highly efficient OER electrocatalyst is reported (labeled as La3IrO7‐SLD), which is obtained by electrochemical activation, and shows better activity and durability than that of commerically available IrO2 as well as most of the reported Ir‐based OER electrocatalysts. At a current density of 10 mA cm−2, the overpotential of La3IrO7‐SLD is 296 mV, which is lower than that of IrO2 (316 mV). Impressively, the increase of potential is less than 50 mV at a voltage–time chronopotentiometry extending for 60 000 s using a glass carbon electrode that is vastly superior to IrO2. Moreover, the mass activity of the catalyst is approximately five times higher than that of IrO2 at 1.60 V versus reversible hydrogen electrode. Density functional theory calculations suggest that a lattice oxygen participating mechanism with central Ir atoms serving as active sites (LOM‐Ir) rationalizes the high activity and durability for the La3IrO7‐SLD electrocatalyst. The favorable energy level of surface active Ir 5d orbitals relative to coordinated O 2p orbitals makes the La3IrO7‐SLD more active.

Ultra-small Sn-RuO2 nanoparticles supported on N‑doped carbon polyhedra for highly active and durable oxygen evolution reaction in acidic media

Electrocatalytic water splitting in acid electrolyte is considered as one of the promising strategies to generate hydrogen. However, the industrial applications of electrolytic water are mainly hindered by the oxygen evolution reaction (OER) due to the high overpotential. Therefore, it is critical to develop highly active and durable electrocatalysts to reduce the overpotential. This work reports ultra-small Sn-RuO2 nanoparticles supported on N‑doped carbon polyhedral are successfully synthesized through dipping and annealing. Integrating the merits of metal–organic frameworks (MOFs) and dopant atoms, the optimized catalyst Sn-RuO2@NPC displays a low overpotential of 178 mV at 10 mA cm−2 and excellent long-term stability after continuous testing of 150 h in the acidic media, which surpassed most Ru-based OER catalysts. The density functional theory (DFT) calculations reveal that doping Sn into RuO2 could effectively improve the intrinsic OER activity of adjacent Ru sites, thereby reducing the Gibbs free energy of rate-determining steps. Notably, the crystal orbital Hamilton population (COHP) shows that the binding strength between catalytic active sites (Ru sites) and reaction intermediates (*O) is decreased due to the presence of Sn, which results in more easily forming the next reaction intermediates (*OOH) and then improving the water splitting activity. This work provides a new insight into an effective method of efficient electrocatalysts for water splitting in acidic media.

SYNTHESIS OF ESTERS OF HALOGENOACETIC ACIDS

Amidoalkylating reagents containing a phthalimide group are used in the synthesis of hard-to-reach primary amines and complex heterocyclic compounds. These types of amidoalkylating compounds are suitable reagents for nucleophilic substituted reactions in acidic media due to their resistance to acids. Result of reactions of amidoalkylating reagents-N-hydroxyethylphthalimide and N-hydroxymethylphthalimide with aliphatic carbonic acids can also produce new bactericidal and fungicidal esters. In this study, halogen acids reacted with N-hydroxymethylphthalimide monochloric acetic acid, monobromic acetic acid, monoiodic acetic acid, trifluoric acetic acid and trichloroacetic acid, as well as, N-b-hydroxyethylphthaleidyl monohydric acid. As a result of the reactions, new phthalimidomethyl and phthalimidoethyl esters of haloacetic acids were synthesized. The physical properties of crystalline esters have been determined. The structure of these compounds were confirmed by the analysis of their IR and PMR spectra. The esterification reactions of halogenated acetic acids were carried out in a benzene solvent and a sulfuric acid catalyst with primary alcohols, N-hydroxymethylphthalimide and N-β- beta hydroxyethylphthalimide,. It was found that in a benzene solvent, which increases the rate of bimolecular nucleophilic exchange in primary alcohols, phthalimidoethyl esters of halogen acid are formed in high yields, and phthalimidomethyl esters are formed in low yields. It was shown that the reaction of esterification of halogen acids with N-hydroxymethylphthalimide proceeds with monomolecular nucleophilic exchange.

Zinc molybdenum oxide sub-micron plates as electro-catalysts for hydrogen evolution reactions in acidic medium

Zinc molybdenum oxide (ZnMoO4) sub-micron plates were efficaciously synthesized by hydrothermal method for electro-catalytic energy conversion applications. Electron microscopic studies show plate like morphology of the synthesized materials. The electrochemical experiments were conducted to investigate the catalytic performance of ZnMoO4 for hydrogen evolution reactions (HER) in acidic medium using 0.5 M H2SO4 electrolyte. The onset over potential, over-potential at 10 mA/cm2, and Tafel of ZnMoO4 sub-micron plates for HER were found to be of ~45 mV, ~140 mV, and ~230 mV/dec respectively.

Facile Synthesis of N-Doped WS2 Nanosheets as an Efficient and Stable Electrocatalyst for Hydrogen Evolution Reaction in Acidic Media

Transition metal chalcogenides have been widely studied as a promising electrocatalyst for the hydrogen evolution reaction (HER) in acidic conditions. Among various transition metal chalcogenides, tungsten disulfide (WS2) is a distinguishable candidate due to abundant active sites and good electrical properties. Herein, we report a facile and selective synthetic method to synthesize WS2 with an intriguing two-dimensional nanostructure by using cysteine (C3H7NO2S) as a chemical agent. In addition, nitrogen can be incorporated during chemical synthesis from cysteine, which may be helpful for enhancing the HER. The electrocatalytic activity of N-doped WS2 exhibits a promising HER in acidic conditions, which are not only higher than W18O49 nanowires and hex-WO3 nanowires, but also comparable to the benchmark Pt/C. Moreover, excellent electrocatalytic stability is also demonstrated for acidic HER during long-term tests, thus highlighting its potential use of practical applications as an electrolyzer.

Ethanol electro-oxidation on carbon-supported Pt3Sn/C, Pt3Cu/C and PtSnCu/C catalysts: CV and in situ FTIR study

Carbon-supported PtSnCu/C, Pt3Sn/C, Pt3Cu/C and Pt/C electrocatalysts were synthesized by chemical reduction of metal precursors in ethanol reflux. These materials were characterized by energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and applied to the ethanol electro-oxidation in acidic medium. The reaction kinetics was studied by cyclic voltammetry and the mechanism was explored by in situ Fourier transform infrared spectroscopy (FTIR). The investigated materials presented chemical composition close to the nominal ones. XRD results indicated the formation of solid solution of Pt and Cu and/or Sn in the bi and tri-metallic materials. The particle size distribution was narrow with mean particle size of around 3 nm. A homogeneous distribution of the nanoparticles over the carbon support was evidenced. The investigated catalysts were active towards the ethanol oxidation reaction in acidic medium and led to the formation of CO2 and carbonyl compounds, as evidenced by FTIR. PtSnCu/C and Pt3Cu/C started to produce CO2 at 0.70 V vs. RHE, while this product was detected only at 0.75 V and 0.80 V vs. RHE on Pt and Pt3Sn/C, respectively, suggesting that Cu improves the dissociative adsorption of ethanol.

Predicting aqueous stability of solid with computed Pourbaix diagram using SCAN functional

In this work, using the SCAN functional, we develop a simple method on top of the Materials Project (MP) Pourbaix diagram framework to accurately predict the aqueous stability of solids. We extensively evaluate the SCAN functional’s performance in computed formation enthalpies for a broad range of oxides and develop Hubbard U corrections for transition-metal oxides where the standard SCAN functional exhibits large deviations. The performance of the calculated Pourbaix diagram using the SCAN functional is validated with comparison to the experimental and the MP PBE Pourbaix diagrams for representative examples. Benchmarks indicate the SCAN Pourbaix diagram systematically outperforms the MP PBE in aqueous stability prediction. We further show applications of this method in accurately predicting the dissolution potentials of the state-of-the-art catalysts for oxygen evolution reaction in acidic media.

A CdS quantum dots-sensitized porphyrin-based MOFs for hydrogen evolution reaction in acid media

Exploiting a renewable and inexpensive electrochemical catalyst for hydrogen evolution reaction (HER) has attracted great attentions recently. In this study, a MOF catalyst CdS@PCN-224(Ni) was fabricated using CdS quantum dots (QDs) and unique PCN-224(Ni) by a simple hydrothermal method. Due to synergetic effect of the CdS QDs and bimetallic porphyrin MOF structure, the special catalyst showed a great electrocatalytic activity with a low overpotential of 120 mV and a current density of 10 mA/cm2 with a Tafel slope of 90.8 mV/dec, which is approaching to that of the Pt/C (42.8 mV/dec). The double-layer capacitances (Cdl) of CdS@PCN-224(Ni) are 9.75 mF/cm2 which is distinctly superior to that of the PCN-224 (2.33 mF/cm2). Even more to the point, this innovative electrochemical catalyst has a wonderful durability in acid solution, which means it could reach a sustainable utilization. In conclusion, the high activity and low-cost catalyst could be a promising candidate for HER devices in acid media.