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1.
Adv Mater ; : e2408461, 2024 Sep 17.
Artículo en Inglés | MEDLINE | ID: mdl-39285843

RESUMEN

Understanding the spin-dependent activity of nitrogen-coordinated single metal atom (M-N-C) electrocatalysts for oxygen reduction and evolution reactions (ORR and OER) remains challenging due to the lack of structure-defined catalysts and effective spin manipulation tools. Herein, both challenges using a magnetic field integrated heterogeneous molecular electrocatalyst prepared by anchoring cobalt phthalocyanine (CoPc) deposited carbon black on polymer-protected magnet nanoparticles, are addressed. The built-in magnetic field can shift the Co center from low- to high-spin (HS) state without atomic structure modification, affording one-order higher turnover frequency, a 50% increased H2O2 selectivity for ORR, and a ≈4000% magnetocurrent enhancement for OER. This catalyst can significantly minimize magnet usage, enabling safe and continuous production of a pure H2O2 solution for 100 h from a 100 cm2 electrolyzer. The new strategy demonstrated here also applies to other metal phthalocyanine-based catalysts, offering a universal platform for studying spin-related electrochemical processes.

2.
J Colloid Interface Sci ; 676: 884-895, 2024 Dec 15.
Artículo en Inglés | MEDLINE | ID: mdl-39067223

RESUMEN

Developing high active and stable cost-effective bifunctional electrocatalysts for overall water splitting to produce hydrogen is of vital significance in clean and sustainable energy development. This work has prepared a novel porous unreported MOF (Ni-DPT) as a precursor to successfully synthesize a non-noble bifunctional NiCoP/Ni12P5@NF electrocatalyst through doping strategy and interface engineering. This catalyst is constructed by layered self-supporting arrays with heterojunction interface and rich nitrogen-phosphorus doping. Structural characterizations and the density function theory (DFT) calculations confirm that the interface effect of NiCoP/Ni12P5 heterojunction can regulate the electronic structure of the catalyst to optimize the Gibbs free energy of hydrogen (ΔGH*); simultaneously, the defect-rich layered nanoarrays can expose more active sites, shorten mass transfer distance, and generate a self-supporting structure for in-situ reinforcing the structural stability. As a result, this NiCoP/Ni12P5@NF catalyst exhibits favorable electrocatalytic performance, which simply needs overpotentials of 100 mV for HER and 310 mV for OER, respectively, at a current density of 10 mA·cm-2. The anion exchange membrane electrolyzer assembled with this NiCoP/Ni12P5@NF as both anode and cathode catalysts can operate stably for 200 h at a current density of 100 mA·cm-2 with an insignificant voltage decrease. This work may provide some inspiration for the further rational design of inexpensive non-noble multifunctional electrocatalysts and electrode materials for water splitting to generate hydrogen.

3.
J Colloid Interface Sci ; 674: 823-833, 2024 Nov 15.
Artículo en Inglés | MEDLINE | ID: mdl-38955013

RESUMEN

Designing and developing suitable oxygen evolution reaction (OER) catalysts with high activity and stability remain challenging in electrolytic water splitting. Hence, NiFe@NC@MoS2 core-bishell composites wrapped by molybdenum disulphide (MoS2) and nitrogen-doped graphene (NC) were prepared using hydrothermal synthesis in this research. NiFe@NC@MoS2 composite exhibits excellent performance with an overpotential of 288 mV and a Tafel slope of 53.2 mV·dec-1 at a current density of 10 mA·cm-2 in 1 M KOH solution, which is superior to commercial RuO2. NC and MoS2 bishells create profuse edge active sites that enhance the adsorption ability of OOH* while lowering the overall overpotential of the product and improving its oxygen precipitation performance. The density function theory(DFT) analysis confirms that the layered MoS2 in NiFe@NC@MoS2 provides additional edge active sites and enhances electron transfer, thus increasing the intrinsic catalytic activity. This research paves a novel way for developing OER electrocatalysts with excellent catalytic performance.

4.
J Colloid Interface Sci ; 675: 712-720, 2024 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-38996701

RESUMEN

Rationally designing metal organic frameworks (MOFs) as an ideal dual-function material for water electrolysis and supercapacitors is of great significance for energy storage and conversion. Herein, we successfully synthesized the nanoneedle-like structure CoNi-MOF by partially replacing 2, 5-thiophenedicarboxylic acid (TDA) with 1, 1'-Ferrocenedicarboxylate (Fc). The exchange of Fc ligand can modulate the morphology and electronic structure of CoNi-TDA, thus exposing the abundant active sites and improving the electrical conductivity. The as-prepared CoNi-TDA/0.2Fc exhibited a low overpotential of 236 mV at 10 mA cm-2 for oxygen evolution reaction (OER) and a low Tafel slope of 40.44 mV dec-1. Additionally, CoNi-TDA/0.2Fc demonstrated a notable specific capacitance of 1409 F g-1 at 1 A/g and excellent stability, maintaining a capacitance retention of 96.54 % after 20,000 cycles. The study proposes a new strategy to modulate the morphology and electronic structure of MOFs via the ligand exchange for high-performance energy storage and conversion device.

5.
Angew Chem Int Ed Engl ; : e202409526, 2024 Jul 20.
Artículo en Inglés | MEDLINE | ID: mdl-39032131

RESUMEN

The development of active, stable, and more affordable electrocatalysts for acidic oxygen evolution reaction (OER) is of great importance for the practical application of electrolyzers and the advancement of renewable energy conversion technologies. Currently, IrO2 is the only catalyst with high stability and activity, but a high cost. Further optimization of the catalyst is limited by the lack of understanding of catalytic behaviors at the acid-IrO2 interface. Here, in strong interaction with the experiment, we develop an explicit model based on grand-canonical density function theory (GC-DFT) calculations to describe acidic OER over IrO2. Compared to the explicit models reported previously, hydronium cations (H3O+) are introduced at the electrochemical interface in the current model. As a result, a variation in stable IrO2 surface configuration under the OER operating condition from previously proposed complete *O-coverage to a mixture coverage of *OH and *O is revealed, which is well supported by in situ Raman measurements. In addition, the accuracy of predicted overpotential is increased in comparison with the experimentally measured. More importantly, an alteration of the potential limiting step from previously identified *O → *OOH to *OH → *O is observed, which opens new opportunities to advance the IrO2-based catalysts for acidic OER.

6.
Chemistry ; 30(47): e202401644, 2024 Aug 22.
Artículo en Inglés | MEDLINE | ID: mdl-38869378

RESUMEN

Herein, a series of monometallic Ni-, Co- and Zn-MOFs and bimetallic NiCo-, NiZn- and CoZn-MOFs of formula M2(BDC)2DABCO and (M,M')2(BDC)2DABCO, respectively, (M, M'=metal) with the same pillar and layer linkers 1,4-diazabicyclo[2.2.2]octane (DABCO) and benzene-1,4-dicarboxylate (BDC) were prepared through a fast microwave-assisted thermal conversion synthesis method (MW) within only 12 min. In the bimetallic MOFs the ratio M:M' was 4 : 1. The mono- and bimetallic MOFs were selected to systematically explore the catalytic-activity of their derived metal oxide/hydroxides for the oxygen evolution reaction (OER). Among all tested bimetallic MOF-derived catalysts, the NiCoMOF exhibits superior catalytic activity for the OER with the lowest overpotentials of 301 mV and Tafel slopes of 42 mV dec-1 on a rotating disk glassy carbon electrode (RD-GCE) in 1 mol L-1 KOH electrolyte at a current density of 10 mA cm-2. In addition, NiCoMOF was insitu grown in just 25 min by the MW synthesis on the surface of nickel foam (NF) with, for example, a mass loading of 16.6 mgMOF/gNF, where overpotentials of 313 and 328 mV at current densities of 50 and 300 mA cm-2, respectively, were delivered and superior long-term stability for practical OER application. The low Tafel slope of 27 mV dec-1, as well as a low reaction resistance from electrochemical impedance spectroscopy (EIS) measurement (Rfar=2 Ω), confirm the excellent OER performance of this NiCoMOF/NF composite. During the electrocatalytic processes or even before upon KOH pre-treatment, the MOFs are transformed to the mixed-metal hydroxide phase α-/ß-M(OH)2 which presents the active species in the reactions (turnover frequency TOF=0.252 s-1 at an overpotential of 320 mV). Compared to the TOF from ß-M(OH)2 (0.002 s-1), our study demonstrates that a bimetallic MOF improves the electrocatalytic performance of the derived catalyst by giving an intimate and uniform mixture of the involved metals at the nanoscale.

7.
J Colloid Interface Sci ; 674: 108-117, 2024 Nov 15.
Artículo en Inglés | MEDLINE | ID: mdl-38917711

RESUMEN

Large-scale hydrogen production by electrocatalytic water splitting still remains as a critical challenge due to the severe catalyst degradation during the oxygen evolution reaction (OER) in acidic media. In this study, we investigate the structural impacts on catalyst degradation behaviors using three iridium-based oxides, namely SrIrO3, Sr2IrO4, and Sr4IrO6 as model catalysts. These Ir oxides possess different connection configurations of [IrO6] octahedra units in their structure. Stable OER performance is observed on SrIrO3 and attributed to the edge-linked [IrO6] structure and rapid formation of a continuous IrOx layer on its surface, which functions not only as the "real" catalyst but also a shield preventing continuous cation leaching (with <1.0 at.% of Ir leaching). In comparison, both Sr2IrO4 and Sr4IrO6 catalysts demonstrate quick current fading with structure transformation to rutile IrO2 and formation of inconducive SrSO4 precipitates on surface, blocking the reactive sites. Nevertheless, over 60 at.% of Ir leaching is detected from the Sr4IrO6 catalyst due to its isolated [IrO6] structure configuration. Results of this work highlight the structural impacts on the catalyst stability in acidic OER conditions.

8.
J Colloid Interface Sci ; 671: 283-293, 2024 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-38810342

RESUMEN

Reinforcing the development of efficient and robust electrocatalysts is pivotal in addressing the challenges associated with oxygen evolution reactions (OER) in water splitting technology. Here, an amorphous/crystalline low-ruthenium-doped bimetallic layered double hydroxide (LDH) electrocatalyst (a/c-CoCu + Rux-LDH/NF) with massive oxygen vacancy on nickel foam was fabricated via ion-exchange and chemical etching, facilitating efficient OER. Among the various catalyst materials tested, the a/c-CoCu + Ru10-LDH/NF exhibits remarkable performance in the OER when employed in an alkaline electrolyte containing 1 M KOH. Achieving a minimal overpotential at 10 mA cm-2 of 214 mV, exhibiting a low Tafel slope value of 64.3 mV dec-1 and exceptional durability lasting for over 100 h. Theoretical calculations demonstrate that the electron structure and d-band center of CoCu-LDH can be effectively regulated through the utilization of a strategy possessing abundant oxygen vacancies and a Ru-doped crystalline/amorphous heterostructure. It will lead to optimized adsorption free energy of reactants and reduced energy barriers for OER. The construction strategy proposed in this paper for catalysts with amorphous/crystalline heterointerfaces offer a novel opportunity to achieve highly efficient OER.

9.
Materials (Basel) ; 17(10)2024 May 07.
Artículo en Inglés | MEDLINE | ID: mdl-38793262

RESUMEN

This study reported a multi-functional Co0.45Fe0.45Ni0.9-MOF/NF catalyst for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting, which was synthesized via a novel shape-preserving two-step hydrothermal method. The resulting bowknot flake structure on NF enhanced the exposure of active sites, fostering a superior electrocatalytic surface, and the synergistic effect between Co, Fe, and Ni enhanced the catalytic activity of the active site. In an alkaline environment, the catalyst exhibited impressive overpotentials of 244 mV and 287 mV at current densities of 50 mA cm-2 and 100 mA cm-2, respectively. Transitioning to a neutral environment, an overpotential of 505 mV at a current density of 10 mA cm-2 was achieved with the same catalyst, showing a superior property compared to similar catalysts. Furthermore, it was demonstrated that Co0.45Fe0.45Ni0.9-MOF/NF shows versatility as a bifunctional catalyst, excelling in both OER and HER, as well as overall water splitting. The innovative shape-preserving synthesis method presented in this study offers a facile method to develop an efficient electrocatalyst for OER under both alkaline and neutral conditions, which makes it a promising catalyst for hydrogen production by water splitting.

10.
Materials (Basel) ; 17(10)2024 May 13.
Artículo en Inglés | MEDLINE | ID: mdl-38793365

RESUMEN

The electrochemical splitting of seawater is promising but also challenging for sustainable hydrogen gas production. Herein, ZIF-67 nanosheets are grown on nickel foam and then etched by Ni2+ in situ to obtain a hierarchical hollow nanosheets structure, which demonstrates outstanding OER performance in alkaline seawater (355 mV at 100 mA cm-2). Diven by a silicon solar panel, an overall electrolysis energy efficiency of 62% is achieved at a high current of 100 mA cm-2 in seawater electrolytes. This work provides a new design route for improving the catalytic activity of metal organic framework materials.

11.
Nano Lett ; 24(20): 6148-6157, 2024 May 22.
Artículo en Inglés | MEDLINE | ID: mdl-38728265

RESUMEN

Magnetic field mediated magnetic catalysts provide a powerful pathway for accelerating their sluggish kinetics toward the oxygen evolution reaction (OER) but remain great challenges in acidic media. The key obstacle comes from the production of an ordered magnetic domain catalyst in the harsh acidic OER. In this work, we form an induced local magnetic moment in the metallic Ir catalyst via the significant 3d-5d hybridization by introducing cobalt dopants. Interestingly, CoIr nanoclusters (NCs) exhibit an excellent magnetic field enhanced acidic OER activity, with the lowest overpotential of 220 mV at 10 mA cm-2 and s long-term stability of 120 h under a constant magnetic field (vs 260 mV/20 h without a magnetic field). The turnover frequency reaches 7.4 s-1 at 1.5 V (vs RHE), which is 3.0 times higher than that without magnetization. Density functional theory results show that CoIr NCs have a pronounced spin polarization intensity, which is preferable for OER enhancement.

12.
ACS Appl Mater Interfaces ; 16(22): 28307-28318, 2024 Jun 05.
Artículo en Inglés | MEDLINE | ID: mdl-38771803

RESUMEN

Bioinspired, self-assembled hybrid materials show great potential in the field of energy conversion. Here, we have prepared a sonication-induced boladipeptide (HO-YF-AA-FY-OH (PBFY); AA = Adipic acid, F = l-phenylalanine, and Y = l-tyrosine) and an anchored, self-assembled nickel-based coordinated polymeric nanohybrid hydrogel (Ni-PBFY). The morphological studies of hydrogels PBFY and Ni-PBFY exhibit nanofibrillar network structures. XPS analysis has been used to study the self-assembled coordinated polymeric hydrogel Ni-PBFY-3, with the aim of identifying its chemical makeup and electronic state. XANES and EXAFS analyses have been used to examine the local electronic structure and coordination environment of Ni-PBFY-3. The xerogel of Ni-PBFY was used to fabricate the electrodes and is utilized in the OER (oxygen evolution reaction). The native hydrogel (PBFY) contains a gelator boladipeptide of 15.33 mg (20 mmol L-1) in a final volume of 1 mL. The metallo-hydrogel (Ni-PBFY-3) is prepared by combining 15.33 mg (20 mmol L-1) of boladipeptide (PBFY) with 3 mg (13 mmol L-1) of NiCl2·6H2O metal in a final volume of 1 mL. It displays an ultralow Tafel slope of 74 mV dec-1 and a lower overpotential of 164 mV at a 10 mA cm-2 current density in a 1 M KOH electrolyte, compared to other electrocatalysts under the same experimental conditions. Furthermore, the Ni-PBFY-3 electrocatalyst has been witnessed to be highly stable during 100 h of chronopotentiometry performance. To explore the OER mechanism in an alkaline medium, a theoretical calculation was carried out by employing the first-principles-based density functional theory (DFT) method. The computed results obtained by the DFT method further confirm that the Ni-PBFY-3 electrocatalyst has a high intrinsic activity toward the OER, and the value of overpotential obtained from the present experiment agrees well with the computed value of the overpotential. The biomolecule-assisted electrocatalytic results provide a new approach for designing efficient electrocatalysts, which could have significant implications in the field of green energy conversion.

13.
ACS Appl Mater Interfaces ; 16(23): 29979-29990, 2024 Jun 12.
Artículo en Inglés | MEDLINE | ID: mdl-38816691

RESUMEN

Development of cheap, highly active, and durable nonprecious metal-based oxygen electrocatalysts is essential for metal-air battery technology, but achieving the balance of oxygen evolution reaction (OER)/oxygen reduction reaction (ORR) bifunctional performance and long-term durability is still a great challenge. Using a typical Co-N-C catalyst as a model, herein, we introduced ammonium chloride into nitrogen-doped carbon materials containing metal elements during the pyrolysis process (Co-N-C/AC), which not only increases the active area but also realizes the accurate customization of the active site (pyridine nitrogen and cobalt oxide species) so as to achieve the balance of the OER/ORR bifunctional sites. The synthesized Co-N-C/AC bifunctional catalyst with a three-dimensional porous structure exhibits a smaller potential gap of 0.72 V. The peak power density of the aqueous cell at a current density of 308 mA cm-2 is 203 mW cm-2. The cycle life (≈3900 h) is longer than those of other recently reported aqueous Zn-air batteries (ZABs). The peak power density of the Co-N-C/AC-based quasi-solid-state ZAB reaches 550 mW cm-2 for ∼72 h. This work shows a feasible path for the practical application of ZABs by balancing the bifunctional electrocatalysts by tailoring the active site reasonably.

14.
Small ; : e2402403, 2024 Apr 29.
Artículo en Inglés | MEDLINE | ID: mdl-38682732

RESUMEN

Viologen-based covalent organic networks represent a burgeoning class of materials distinguished by their captivating properties. Here, supramolecular chemistry is harnessed to fabricate polyrotaxanated ionic covalent organic polymers (iCOP) through a Schiff-base condensation reaction under solvothermal conditions. The reaction between 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-diium dichloride (DPV-NH2) and 1,3,5-triformylphloroglucinol (TPG) in various solvents yields an iCOP-1 and iCOP-2. Likewise, employing cucurbit[7]uril (CB[7]) in the reaction yielded polyrotaxanated iCOPs, denoted as iCOP-CB[7]-1 and iCOP-CB[7]-2. All four iCOPs exhibit exceptional stability under the acidic and basic conditions. iCOP-CB[7]-2 displays outstanding electrocatalytic Oxygen Evolution Reaction (OER) performance, demanding an overpotential of 296 and 332 mV at 10 and 20 mA cm-2, respectively. Moreover, the CB[7] integrated iCOP-2 exhibits a long-term stable nature for 30 h in 1 m KOH environment. Further, intrinsic activity studies like TOF show a 4.2-fold increase in generation of oxygen (O2) molecules than the bare iCOP-2. Also, it is found that iCOP-CB[7]-2 exhibits a high specific (19.48 mA cm-2) and mass activity (76.74 mA mg-1) at 1.59 V versus RHE. Operando-EIS study evident that iCOP-CB[7]-2 commences OER at a relatively low applied potential of 1.5 V versus RHE. These findings pave the way for a novel approach to synthesizing various mechanically interlocked molecules through straightforward solvothermal conditions.

15.
Sci Rep ; 14(1): 9821, 2024 Apr 29.
Artículo en Inglés | MEDLINE | ID: mdl-38684728

RESUMEN

Dimensionally stable anodes of titanium (Ti) metal coated with mixed metal oxides (MMO) are widely used in several electrochemical applications, especially chloro-alkali electrolysis. Herein, we deposited MMO coatings on Ti substrates in different compositions, namely, (60%RuO2-40%TiO2), (60%RuO2-30%TiO2-10%IrO2), and (60%RuO2-20%TiO2-15%IrO2-5%Ta2O5), where RuO2 has the same percentage ratio in all coatings. The aim was to use these electrodes for chlorine evolution reaction (CER) and oxygen evolution reaction (OER) applications. Electrochemical characterization of the coated samples was performed to identify the best Ti/MMO electrodes with the highest efficiencies among the various prepared combinations. The role of IrO2 and Ta2O5 in enhancing corrosion resistance and electrochemical efficacy was up for debate. Scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses were exploited to determine the surface morphology, chemical composition, crystallinity, surface composition, and chemical states of the acquired coatings. The differential scanning calorimetry (DSC) method was used to evaluate the apparent activation energy ( E a ) of the deposited MMO. Additionally, the electrochemical performance of our designed coatings was scrutinized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), a current on-off test, a CV stability test (ST), and an accelerated stability test (AST). Furthermore, linear sweep voltammetry (LSV) was incorporated to assess the catalytic efficacy of the prepared anodes toward the CER in a brine solution of pH 2 and the OER in 1 M H2SO4. It became clear that the CER and OER incurred almost the same potential value (1.1 V) on both Ti/RuO2-TiO2 and Ti/RuO2-TiO2-IrO2 electrodes. However, on the Ti/RuO2-TiO2-IrO2-Ta2O5 anode, there was a 0.2 V potential difference between the CER occurring at 1.1 V and the OER happening at 1.3 V.

16.
ACS Appl Mater Interfaces ; 16(10): 12339-12352, 2024 Mar 13.
Artículo en Inglés | MEDLINE | ID: mdl-38425008

RESUMEN

Progress in electrochemical water-splitting devices as future renewable and clean energy systems requires the development of electrodes composed of efficient and earth-abundant bifunctional electrocatalysts. This study reveals a novel flexible and bifunctional electrode (NiO@CNTR) by hybridizing macroscopically assembled carbon nanotube ribbons (CNTRs) and atmospheric plasma-synthesized NiO quantum dots (QDs) with varied loadings to demonstrate bifunctional electrocatalytic activity for stable and efficient overall water-splitting (OWS) applications. Comparative studies on the effect of different electrolytes, e.g., acid and alkaline, reveal a strong preference for alkaline electrolytes for the developed NiO@CNTR electrode, suggesting its bifunctionality for both HER and OER activities. Our proposed NiO@CNTR electrode demonstrates significantly enhanced overall catalytic performance in a two-electrode alkaline electrolyzer cell configuration by assembling the same electrode materials as both the anode and the cathode, with a remarkable long-standing stability retaining ∼100% of the initial current after a 100 h long OWS run, which is attributed to the "synergistic coupling" between NiO QD catalysts and the CNTR matrix. Interestingly, the developed electrode exhibits a cell potential (E10) of only 1.81 V with significantly low NiO QD loading (83 µg/cm2) compared to other catalyst loading values reported in the literature. This study demonstrates a potential class of carbon-based electrodes with single-metal-based bifunctional catalysts that opens up a cost-effective and large-scale pathway for further development of catalysts and their loading engineering suitable for alkaline-based OWS applications and green hydrogen generation.

17.
Molecules ; 29(3)2024 Jan 31.
Artículo en Inglés | MEDLINE | ID: mdl-38338401

RESUMEN

Transition metal phosphides (TMPs) have been widely studied for water decomposition for their monocatalytic property for anodic or cathodic reactions. However, their bifunctional catalytic activity still remains a major challenge. Herein, hexagonal nickel-cobalt bimetallic phosphide nanoneedles with 1-3 µm length and 15-30 nm diameter supported on NF (NixCo2-xP NDs/NF) with adjusted electron structure have been successfully prepared. The overall alkaline water electrolyzer composed of the optimal anode (Ni0.67Co1.33P NDs/NF) and cathode (Ni1.01Co0.99P NDs/NF) provide 100 mA cm-2 at 1.62 V. Gibbs Free Energy for reaction paths proves that the active site in the hydrogen evolution reaction (HER) is Ni and the oxygen evolution reaction (OER) is Co in NixCo2-xP, respectively. In the HER process, Co-doping can result in an apparent accumulation of charge around Ni active sites in favor of promoting HER activity of Ni sites, and ΔGH* of 0.19 eV is achieved. In the OER process, the abundant electron transfer around Co-active sites results in the excellent ability to adsorb and desorb *O and *OOH intermediates and an effectively reduced ∆GRDS of 0.37 eV. This research explains the regulation of electronic structure change on the active sites of bimetallic materials and provides an effective way to design a stable and effective electrocatalytic decomposition of alkaline water.

18.
Small ; 20(26): e2309689, 2024 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-38258384

RESUMEN

Developing efficient water-splitting electrocatalysts to accelerate the slow oxygen evolution reaction (OER) kinetics is urgently desired for hydrogen production. Herein, ultralow phosphorus (P)-doped NiFe LDH (NiFePx LDH) with mild compressive strain is synthesized as an efficient OER electrocatalyst. Remarkably, NiFePx LDH with the phosphorus mass ratio of 0.32 wt.% and compressive strain ratio of 2.53% (denoted as NiFeP0.32 LDH) exhibits extraordinary OER activity with an overpotential as low as 210 mV, which is superior to that of commercial IrO2 and other reported P-based OER electrocatalysts. Both experimental performance and density function theory (DFT) calculation demonstrate that the doping of P atoms can generate covalent Fe─P coordination bonds and lattice distortion, thus resulting in the consequent depletion of electrons around the Fe active center and the downward shift of the d-band center, which can lead to a weaker adsorption ability of *O intermediate to improve the catalytic performance of NiFeP0.32 LDH for OER. This work provides novel insights into the distinctive coordinated configuration of P in NiFePx LDH, which can result in superior catalytic performance for OER.

19.
ACS Appl Mater Interfaces ; 16(3): 3260-3269, 2024 Jan 24.
Artículo en Inglés | MEDLINE | ID: mdl-38221720

RESUMEN

The anode stability is critical for efficient and reliable seawater electrolyzers. Herein, a NiFe-based film catalyst was prepared by anodic oxidation to serve as a model electrode, which exhibited a satisfactory oxygen evolution performance in simulated alkaline seawater (1 M KOH + 0.5 M NaCl) with an overpotential of 348 mV at 100 mA cm-2 and a long-term stability of over 100 h. After that, the effects of the current density and bulk pH of the electrolyte on its stability were evaluated. It was found that the electrode stability was sensitive to electrolysis conditions, failing at 20 mA cm-2 in 0.1 M KOH + 0.5 M NaCl but over 500 mA cm-2 in 0.5 M KOH + 0.5 M NaCl. The electrode dissolved, and some precipitates immediately formed at the region very close to the electrode surface during the electrolysis. This can be ascribed to the pH difference between the electrode/electrolyte interface and the bulk electrolyte under anodic polarization. In other words, the microzone acidification accelerates the corrosion of the electrode by Cl-, thus affecting the electrode stability. The operational performances of the electrode under different electrolysis conditions were classified to further analyze the degradation behavior, which resulted in three regions corresponding to the stable oxygen evolution, violent dissolution-precipitation, and complete passivation processes, respectively. Thereby increasing the bulk pH could alleviate the microzone acidification and improve the stability of the anode at high current densities. Overall, this study provides new insights into understanding the degradation mechanism of NiFe-based catalysts and offers electrolyte engineering strategies for the application of anodes.

20.
Small ; 20(5): e2304636, 2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-37789503

RESUMEN

The development of electrocatalysts that are not reliant on iridium for efficient acid-oxygen evolution is a critical step towards the proton exchange membrane water electrolysis (PEMWE) and green hydrogen industry. Ruthenium-based electrocatalysts have garnered widespread attention due to their remarkable catalytic activity and lower commercial price. However, the challenge lies in balancing the seesaw relationship between activity and stability of these electrocatalysts during the acid-oxygen evolution reaction (OER). This review delves into the progress made in Ru-based electrocatalysts with regards to acid OER and PEMWE applications. It highlights the significance of customizing the acidic OER mechanism of Ru-based electrocatalysts through the coordination of adsorption evolution mechanism (AEM) and lattice oxygen oxidation mechanism (LOM) to attain the ideal activity and stability relationship. The promising tradeoffs between the activity and stability of different Ru-based electrocatalysts, including Ru metals and alloys, Ru single-atomic materials, Ru oxides, and derived complexes, and Ru-based heterojunctions, as well as their applicability to PEMWE systems, are discussed in detail. Furthermore, this paper offers insights on in situ control of Ru active sites, dynamic catalytic mechanism, and commercial application of PEMWE. Based on three-way relationship between cost, activity, and stability, the perspectives and development are provided.

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