Superior Electrocatalytic Activity Research Articles

High-Entropy Oxide of (BiZrMoWCeLa)O2 as a Novel Catalyst for Vanadium Redox Flow Batteries.

In this study, new fluorite high-entropy oxide (HEO), (BiZrMoWCeLa)O2, nanoparticles were produced using a surfactant-assisted hydrothermal technique followed by calcination and were used as novel catalytic materials for vanadium redox flow batteries (VRFBs). The HEO calcined at 750 °C (HEO-750) demonstrates superior electrocatalytic activity toward V3+/V2+ and VO2+/VO2+ redox couples compared to those of cells assembled with other samples. The charge-discharge tests further confirm that VRFBs using the HEO-750 catalyst demonstrate excellent Coulombic efficiency, voltage efficiency, and energy efficiency of 97.22, 87.47, and 85.04% at a current density of 80 mA cm-2 and 98.10, 74.76, and 73.34% at a higher current density of 160 mA cm-2, respectively. Moreover, with 500 charge-discharge cycles, there is no discernible degradation. These results are attributed to the calcination heat treatment, which induces the formation of a new single-phase fluorite structure, which facilitates the redox reactions of the vanadium redox couples. Furthermore, a high surface area, wettability, and plenty of oxygen vacancies can give more surface electroactive sites, improving the electrochemical performance, the charge transfer of the redox processes, and the stability of the VRFBs' electrode. This is the first report on the development of fluorite structure HEO nanoparticles in VRFBs, and it opens the door to further research into other HEOs.

Rational Construction of 3D Self-Supported MOF-Derived Cobalt Phosphide-Based Hollow Nanowall Arrays for Efficient Overall Water Splitting At large Current Density.

Developing efficient nonprecious bifunctional electrocatalysts for hydrogen and oxygen evolution reactions (HER and OER) in the same electrolyte with a low overpotential and large current density presents an appealing yet challenging goal for large-scale water electrolysis. Herein, a unique 3D self-branched hierarchical nanostructure composed of ultra-small cobalt phosphide (CoP) nanoparticles embedded into N, P-codoped carbon nanotubes knitted hollow nanowall arrays (CoPʘNPCNTs HNWAs) on carbon textiles (CTs) through a carbonization-phosphatization process is presented. Benefiting from the uniform protrusion distributions of CoP nanoparticles, the optimum CoPʘNPCNTs HNWAs composites with high abundant porosity exhibit superior electrocatalytic activity and excellent stability for OER in alkaline conditions, as well as for HER in both acidic and alkaline electrolytes, even under large current densities. Furthermore, the assembled CoPʘNPCNTs/CTs||CoPʘNPCNTs/CTs electrolyzer demonstrates exceptional performance, requiring an ultralow cell voltage of 1.50V to deliver the current density of 10mAcm-2 for overall water splitting (OWS) with favorable stability, even achieving a large current density of 200mAcm-2 at a low cell voltage of 1.78V. Density functional theory (DFT) calculation further reveals that all the C atoms between N and P atoms in CoPʘNPCNTs/CTs act as the most efficient active sites, significantly enhancing the electrocatalytic properties. This strategy, utilizing 2D MOF arrays as a structural and compositional material to create multifunctional composites/hybrids, opens new avenues for the exploration of highly efficient and robust non-noble-metal catalysts for energy-conversion reactions.

Synergism of Holmium Orthovanadate/Phosphorus-Doped Carbon Nitride Nanocomposite: Nonenzymatic Electrochemical Detection of Hydrogen Peroxide.

Developing efficient and robust electrode materials for electrochemical sensors is critical for real-time analysis. In this paper, a hierarchical holmium vanadate/phosphorus-doped graphitic carbon nitride (HoVO4/P-CN) nanocomposite is synthesized and used as an electrode material for electrochemical detection of hydrogen peroxide (H2O2). The HoVO4/P-CN nanocomposite exhibits superior electrocatalytic activity at a peak potential of -0.412 V toward H2O2 reduction in alkaline electrolytes while compared with other reported electrocatalysts. The HoVO4/P-CN electrochemical platform operated under the optimized conditions shows excellent analytical performance for H2O2 detection with a linear concentration range of 0.009-77.4 μM, a high sensitivity of 0.72 μA μM-1 cm-2, and a low detection limit of 3.0 nΜ. Furthermore, the HoVO4/P-CN-modified electrode exhibits high selectivity, remarkable stability, good repeatability, and satisfactory reproducibility in detecting H2O2. Its superior performance can be attributed to a large specific surface area, high conductivity, more active surface sites, unique structure, and synergistic action of HoVO4 and P-CN to benefit enhanced electrochemical activity. The proposed HoVO4/P-CN electrochemical platform is effectively applied to ascertain the quantity of H2O2 in food and biological samples. This work outlines a promising and effectual strategy for the sensitive electrochemical detection of H2O2 in real-world samples.

Functionality Modulation Toward Thianthrene-based Metal-Free Electrocatalysts for Water Splitting.

The development of metal-free bifunctional electrocatalysts for hydrogen and oxygen evolution reactions (HER and OER) is significant but rarely demonstrated. Porous organic polymers (POPs) with well-defined electroactive functionalities show superior performance in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Precise control of the active sites' local environment requires careful modulation of linkers through the judicious selection of building units. Here, a systematic strategy is introduced for modulating functionality to design and synthesize a series of thianthrene-based bifunctional sp2 C═C bonded POPs with hollow spherical morphologies exhibiting superior electrocatalytic activity. This precise structural tuning allowed to gain insight into the effects of heteroatom incorporation, hydrophilicity, and variations in linker length on electrocatalytic activity. The most efficient bifunctional electrocatalyst THT-PyDAN achieves a current density of 10 mA cm─2 at an overpotential (η10) of ≈65 mV (in 0.5 m H2SO4) and ≈283 mV (in 1 m KOH) for HER and OER, respectively. THT-PyDAN exhibits superior activity to all previously reported metal-free bifunctional electrocatalysts in the literature. Furthermore, these investigations demonstrate that THT-PyDAN maintains its performance even after 36 h of chronoamperometry and 1000 CV cycling. Post-catalytic characterization using FT-IR, XPS, and microscopic imaging techniques underscores the long-term durability of THT-PyDAN.

Enhanced lanthanum-stabilized low crystallinity metal oxide electrocatalysts with superior activity for oxygen reactions

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are key electrochemical reactions for the development of rechargeable Zn-air batteries. However, due to the high cost of commercial noble metal-based catalysts and their limited bifunctionality, it is necessary the design of new electrocatalysts. In this study, stable electrocatalysts have been synthesized through a hydrothermal method and further low-temperature thermal treatment. The materials consist of La stabilized low crystallinity Mn and Co metal (hydro-)oxides. The electrocatalytic performance of these materials has been compared with counterparts calcined at higher temperatures. The findings demonstrate that materials synthesized at lower temperatures and with low crystallinity exhibit superior electrocatalytic activity for both ORR and OER. Moreover, the research highlights the favorable influence of the lanthanum cation, which enhances changes of surface morphology and oxidation states of other cations (Mn and Co). Additionally, the positive contribution of the carbon component to electrochemical activity and electrical conductivity has been elucidated. The best electrocatalyst was studied in a rechargeable Zn-air battery with a durability of up to 120 h. They exhibited better stability and performance than the commercial Pt/C + RuO2 catalyst currently used.

An organic–inorganic hybrid method to fabricate bimetallic phosphide nanospheres as efficient electrocatalyst for hydrogen evolution reaction

Hydrogen evolution reaction (HER) serves as a crucial half reaction in electrolytic water splitting. Pt is deemed to the most active HER electrocatalyst, but the scarcity and high cost of Pt limit its massive application. Developing efficient, low-cost and well-structured HER catalysts is quite vital for advancing the development of water electrolysis technology. Herein, we present a facile organic–inorganic hybrid method to achieve a novel bimetallic phosphide of MoP-RuPx/NPC catalyst, showing superior electrocatalytic activity with an overpotential of 24 and 94 mV at 10 mA cm−2 in alkaline and acid media, respectively. Moreover, MoP-RuPx/NPC also exhibits an outstanding electrochemical stability with a negligible degradation in HER activity after long-term stability measurements. The eminent electrocatalytic performance of MoP-RuPx/NPC catalyst should be ascribed to the high surface specific area, multiple heterogeneous interfaces, strong electronic synergistic effect between MoP and RuPx, and abundant defects. The organic–inorganic hybrid strategy implemented in this work can be used for synthesizing other bimetallic phosphide catalysts.

Effect of Synchrotron X-ray Irradiation Time on the Particle Size and DFAFC Performance of Pd/CNT Catalysts.

Global energy sources are limited, and energy requirements are ever-increasing due to the demand for developments in human life and technology. The environmentally friendly direct formic acid fuel cell (DFAFC) is an attractive electronic device due to its clean energy. In a DFAFC, an anodic catalyst plays an important role concerning the oxidation pathway and activity. In the present study, palladium (Pd) was synthesized by synchrotron X-ray photoreduction using various irradiation times (0.5-4 min) to control the particle size. An acid-treated carbon nanotube (A-CNT) was used as the template for Pd deposition. The A-CNT and Pd/A-CNT were examined using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and transmission electron microscopy to reveal the microstructural characteristics. Electrochemical evaluation, electrocatalytic activity, and the DFAFC performance of so-obtained Pd/A-CNT catalysts were investigated. The experiment's results showed that the Pd/A-CNT-2 (i.e., synchrotron photoreduction for 2 min) underwent a direct formic acid oxidation pathway and possessed a high ECSA value of 62.59 m2/gPd and superior electrocatalytic activity of 417.7 mA/mgPd. In a single DFAFC examination, the anodic Pd/A-CNT-2 catalyst had a power density of 106.2 mW/mgPd and a relatively long lifetime of 2.91 h. Pd/A-CNT-2 anodic catalysts synthesized by surfactant-free synchrotron X-ray photoreduction with a rapid processing time (2 min) are potential candidates for DFAFC applications.

Synergistic promotion of electrocatalytic activities and multilevel descriptors in nitrogen-doped graphene supported dual-atom catalysts for lithium-sulfur batteries

Lithium-sulfur battery (LSB) is emerging as one of the most promising candidates in energy storage systems, but its performance is greatly limited by the polysulfide shuttle and sluggish reaction kinetics. Here, we focus on 18 dual-atom catalysts (DACs) supported by nitrogen-doped graphene with three types of metal coordination environment, namely M1M2Nx (M1, M2 = Fe, Co, Ni and x = 6 or 8), for sulfur redox by using first-principles calculations. Our results show that most DACs exhibit enhanced anchoring capacity toward polysulfides and superior electrocatalytic activity via a synergistic effect between the bimetallic sites. Among them, FeNiN8 presents balanced bifunctional catalytic activities with reduced Gibbs free energy change during the conversion of Li2S4 to Li2S (1.091 eV) and decomposition barrier of Li2S (1.330 eV) to boost reaction kinetics during charge-discharge cycling, surpassing single-atom counterparts. In particular, multilevel descriptors correlating the target catalytic properties with adsorption energies of key sulfur species, ICOHP of M-S atom pairs, and the fundamental geometric and electronic properties are identified to characterize the catalytic activities of DACs. Extended DACs to other 3d transition metals further demonstrate the effective design strategy and their broad application prospects in LSBs, which contributes to a deep understanding of the origin of catalytic activity of dual-atom sites.

Sulfide-based Mo-MOF derived bifunctional electrocatalysts for direct methanol fuel cells

In this paper, an effective method for synthesizing three different catalysts Mo-MOF, MO/NPC, and MO-MS/NPC by solvothermal preparation and pyrolysis processes has been described. The structural and compositional characteristics of these catalysts have been thoroughly analyzed using SEM, XRD, XPS, FTIR, and TEM characterization techniques. It is noteworthy that MO-MS/NPC has proven to have remarkable electrocatalytic capabilities, exhibiting high current density i.e., 354.3 mA/cm2 and stability in methanol oxidation as well as superior electrocatalytic activity for oxygen reduction reactions Because of these qualities, MO-MS/NPC, MO/NPC, and Mo-MOF might be an attractive option as cathodic and anodic materials in direct methanol fuel cells (DMFCs). Their higher oxygen reduction abilities as cathode materials can boost the cathodic reaction's effectiveness and encourage the conversion of oxygen and protons into water, and also help methanol to oxidize into carbon dioxide at the anode, liberating electrons that can be used to produce electricity.

Superior electrocatalytic hydrogen evolution activity of a triply bridged diruthenium(II) complex on a carbon cloth support.

This article describes the structural authentication of a unique triply bridged [1](ClO4)2 and monomeric [2]ClO4/[3]ClO4. Electrochemical HER on a carbon cloth support demonstrated the superior performance of [1](ClO4)2 with high TON (>105) and its long-term stability. The primary kinetic isotope effect of [1](ClO4)2 revealed the involvement of PCET in the rate-determining step.

Photo-electro concerted catalysis of a highly active Pt/CoP/C nanocomposite for the hydrogen evolution reaction

A facile phosphorus doping method was used to synthesize Pt/CoP/C exhibiting superior photo electro-catalytic activity toward HER, and H2 amount reaches 5384.18 mmol h−1 g−1 under irradiation, displaying a cost-effective catalytic capacity of Pt.

Electrodeposited Ni-Sn-P electrodes for hydrogen evolution electrocatalysis

Developing high-activity, Nobel metal-free electrodes is of utmost significance in the context of the hydrogen evolution reaction (HER). In this study, we employed an electrodeposited process to fabricate Ni-Sn-P films on a copper substrate. The microstructure and electrocatalytic properties of these Ni-Sn-P films were thoroughly characterized and subsequently compared to those of the reference Ni-P films.Remarkably, the Ni-Sn-P electrode exhibited an impressively low overpotential of −84 mV at a current density of −10 mA cm−2 in a 1 M NaOH solution. This value was found to be 172 mV lower than that of the Ni-P electrode, thereby establishing the superior electrocatalytic activity of the Ni-Sn-P electrode. Moreover, the excellent electrocatalytic stability of the Ni-Sn-P electrode was demonstrated over a time span of at least 25 h.The exceptional attributes of the Ni-Sn-P electrode can be ascribed to its larger active surface area, lower Tafel slope, and reduced charge transfer resistance. The utilization of Ni-Sn-P films as electrode materials holds great potential in advancing the field of HER due to their enhanced performance compared to conventional Ni-P films.

Bi-metallic [Cu/Co(6mna)2]n metal organic chalcogenolate frameworks as high-performance electro-catalysts for dye-sensitized solar cells: a ligand-assisted bottom-up synthesis

Superior electro-catalytic activity of a heterogeneous bi-metallic [Cu/Co(6mna)2]n MOF was established by synergistic effects between conductive [Cu2(6mna)(6mn)NH4]n with 2D (–Cu–S–)n planes and porous [Co2(6mna)2]n with helical (–Co–S–)n chains.

Fabrication of a free-standing Ti3C2T x -PTh counter electrode via interfacial polymerization for dye-sensitized solar cells.

The current work involves the fabrication of a MXene-Polythiophene (Ti3C2T x -PTh) composite via interfacial polymerization, alongside its deployment as a counter electrode (CE) or photocathode in dye-sensitized solar cells (DSSCs). The structural properties of the synthesized materials were investigated through a comprehensive array of techniques, including X-ray diffraction (XRD), fourier-transform infrared (FT-IR) spectroscopy, high resolution scanning electron microscopy (HRSEM), energy-dispersive X-ray analysis (EDAX), and X-ray photoelectron spectroscopy (XPS). The electrochemical performance, assessed via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), revealed that the Ti3C2T x -PTh CE exhibits superior electro-catalytic activity, and reduction in charge transfer resistance compared to other individual CEs. These observations are in concordance with the data obtained from Tafel analysis. The incorporation of Ti3C2T x sheets into the composite significantly augmented its catalytic efficacy for triiodide reduction, manifesting in elevated short-circuit photocurrent density and enhanced fill factor metrics. A DSSC utilizing the Ti3C2T x -PTh CE exhibited a power conversion efficiency (PCE) of 5.83%, which stands on par with that of traditional Pt CEs. Thus, the Ti3C2T x -PTh CE material is posited as a viable, cost-efficient alternative to Pt, heralding a new era in the engineering of counter electrodes for the next generation of DSSCs.

Mono-, bi- and tri-metallic Fe-based platinum group metal-free electrocatalysts derived from phthalocyanine for oxygen reduction reaction in alkaline media.

In this manuscript, a comprehensive study is presented on Fe-based electrocatalysts with mono, bi, and tri-metallic compositions, emphasizing the influence of processing-structure correlations on the electrocatalytic activity for the oxygen reduction reaction (ORR) in the alkaline medium. These electrocatalysts were synthesized through the mixing of transition metal phthalocyanines (TM-Pc) with conductive carbon support, followed by controlled thermal treatment at specific temperatures (600 °C and 900 °C). An extensive analysis was conducted, employing various techniques, including X-ray Absorption Spectroscopy (XAS), Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD), providing valuable insights into the structural characteristics of the synthesized nanoparticles. Importantly, an increase in the Fe-Pc weight percentage from 10% to 30% enhanced the ORR activity, although not proportionally. Furthermore, a comparative analysis between mono, bi, and tri-metallic samples subjected to different functionalization temperatures highlighted the superior electrocatalytic activity of electrocatalysts functionalized at 600 °C, particularly Fe 600 and Fe-Ni-Cu 600. These electrocatalysts featured Eon values of 0.96 V vs. RHE and E1/2 values of 0.9 V vs. RHE, with the added benefit of reduced anionic peroxide production. The potential of these Fe-based electrocatalysts to enhance ORR efficiency is underscored by this research, contributing to the development of more effective and sustainable electrocatalysts for energy conversion technologies.

Intermetallic MnNi3 phase separated from nanoporous nickel as hydrogen evolution electrocatalyst in basic media

Dealloying-derived intermetallic MnNi3 possesses porous-ligament structure with an ultra-large specific surface area, exhibiting superior electrocatalytic activity and robustness towards alkaline hydrogen evolution and industrial water electrolysis.

Boosted urea electrooxidation activity by dynamic steady blending CoOOH–Ni(OH)2 nanoclusters for H2 production in a pH-asymmetric electrolyzer

The blending CoOOH–Ni(OH)2 nanoclusters exhibited superior electrocatalytic activity for urea oxidation reaction in alkaline environment, achieving low onset potential of 1.24 V (vs. RHE).

Novel sulfate solid supported binary Ru-Ir oxides for superior electrocatalytic activity towards OER and CER

Electrolysis for producing hydrogen powered by renewable electricity can be dramatically expanded by adapting different electrolytes (brine, seawater or pure water), which means the anode materials must stand up to complex electrolyte conditions. Here, a novel catalyst/support hybrid of binary Ru3.5Ir1Ox supported by barium strontium sulfate (BaSrSO4) was synthesized (RuIrOx/BSS) by exchanging the anion ligands of support. The as-synthesized RuIrOx/BSS exhibits compelling oxygen evolution (OER) and chlorine evolution (CER) performances, which affords to 10 mA cm−2 with only overpotential of 244 mV and 38 mV, respectively. The performed X-ray adsorption spectra clearly indicate the presence of an interface charge transfer effect, which results in the assignment of more electrons to the d orbitals of the Ru and Ir sites. The theoretical calculations demonstrated that the electronic structures of the catalytic active sites were modulated to give a lower overpotential, confirming the intrinsically high OER and CER catalytic activity.

Cobalt–organic framework as a Bi–functional electrocatalyst for renewable hydrogen production by electrochemical water splitting

Sustainable hydrogen production by electrocatalytic water splitting is an attractive approach to establish a carbon–free future. On the other hand, the operationalization of this technology on a large scale requires the design and synthesis of efficient electrocatalysts to promote hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Metal–organic frameworks (MOFs) have provided new opportunities in the field of electrocatalytic water splitting due to their unique properties. Herein, we report an affordable, simple, and environmentally friendly strategy for the synthesis of Co3(BTC)2 MOF electrocatalyst in distilled water at room temperature. Surprisingly, Co3(BTC)2 demonstrated superior electrocatalytic activity toward HER and OER in alkaline media. The Co3(BTC)2 requires overpotentials of 450 and 370mV for HER and OER to achieve a current density of 10mA cm−2, respectively.

NiFe codoping-regulated amorphous/crystalline heterostructured Co-based hydroxides/tungstate with rich oxygen vacancies for efficient water oxidation catalysis

Oxygen evolution reaction (OER) is a crucial half-reaction in water splitting, generating hydrogen for sustainable development, but it is often subject to sluggish kinetics. Abundant transition metal-based OER electrocatalysts have been utilized to expedite the process. However, traditional amorphous catalysts suffer from low conductivity, while the activity of crystalline catalysts is also unsatisfactory. Herein, an amorphous/crystalline heterostructured Co-based hydroxide/tungstate was meticulously constructed and further tailored using a NiFe codoping method (NiFeCoW). Following NiFe codoping, the electronic structure had been modulated, subsequently altering the adsorption toward intermediates. From the electrochemical measurements, the NiFeCoW catalyst demonstrated superior electrocatalytic activity for OER in alkaline media, with a minimal overpotential of 297 mV at 10 mA cm−2 and a cell voltage of 1.57 V for water splitting. This study provides valuable guidance for regulating the amorphous/crystalline heterophase in catalysts through bimetallic modulating engineering.