Cobalt Phosphide (Co2P) with Notable Electrocatalytic Activity Designed for Sensitive and Selective Enzymeless Bioanalysis of Hydrogen Peroxide

Trace Ru Incorporation Boosted Co2P Nanorods for Superior Water Electrolysis and Substrate-Paired Electrolysis Toward Value-Added Chemicals in Alkaline Medium

Electro-valorization of biomass-derived chemicals has ensured sustainable production of value-added products, an effective approach for reducing carbon footprint, through renewable energy. Electrochemical oxidation and reduction reactions in aqueous media using H2O as a potential source for active hydrogenated and oxygenated species fulfill the purpose. In this study, Ru─Co2P nanorods are explored as a bifunctional electrocatalyst toward valorization of Organics at basic media. The in-situ electrogenerated Co3+ and Co4+ species act as active oxidants toward product selectivity. An overpotential of 68 mV is found for hydrogen evolution reaction (1 m NaOH) with Ru─Co2P. Further, used as cathode, Ru─Co2P effectively reduces furfuraldehyde to furfuryl alcohol and p-nitrophenol to p-aminophenol. Ru doping enables ease of formation of active species both for reduction and oxidation, faster charge transfer between catalyst to absorbates. Density Functional Theory calculation establishes Ru incorporation in Co2P surface results in enhanced adsorption of substrates. Ru doping modulates the electronic structure of Co2P which changes the density of states resulting in faster water dissociation and water splitting. To reach 10 mA cm-2 current density only 1.6 V is required for water electrolysis, whereas 1.4 V is enough for substrate-paired electrolysis with simultaneous oxidation of benzyl alcohol and reduction of p-nitro phenol.

ZIF-67-derived Co-N-C supported nickel cobalt sulfide as a bifunctional electrocatalyst for sustainable hydrogen production via alkaline electrolysis

As non-renewable resources are finite and cannot be utilized indefinitely, hydrogen (H2) has emerged as a promising alternative for clean and sustainable energy. The cost-effective hydrogen production to meet large-scale commercial demand poses a significant challenge. Water electrolysis, powered by electricity derived from renewable resources, stands out as a viable route towards sustainable hydrogen production, with electrocatalysis playing a pivotal role in this process. Notably, materials derived from metal-organic frameworks (MOFs) exhibit excellent physicochemical properties, making them promising candidates for electrocatalysis. In this study, we synthesized zeolitic imidazolate framework-67 (ZIF-67) and its derived Co-N-doped carbon (Co-N-C) supported NiCo2S4 on nickel foam (NF), namely NF@ZIF-67@NiCo2S4 and NF@Co-N-C@NiCo2S4, using a hydrothermal method. The electrocatalytic activity of these synthesized materials for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) was systematically evaluated using various electrochemical techniques. The NF@ZIF-67@NiCo2S4 material demonstrates overpotentials of 248 and 359 mV for OER and HER at the current density of 50 mA cm-2, whereas, NF@Co-N-C@NiCo2S4 exhibits overpotentials of 239 and 351 mV, respectively. Furthermore, the catalysts exhibit excellent stability in both OER and HER even under high applied potentials. Moreover, to assess their catalytic performance in a full-cell configuration, two alkaline electrolyzer cells were assembled: NF@ZIF-67@NiCo2S4(+)∥NF@ZIF-67@NiCo2S4(-) and NF@Co-N-C@NiCo2S4(+)∥NF@Co-N-C@NiCo2S4(-). These two electrolyzers demonstrated cell potentials of 1.62 V and 1.59 V at 10 mA cm-2, respectively, showcasing their efficacy in overall water-splitting.

Regioselective Hydroboration of Unsymmetrical Internal Alkynes Catalyzed by a Cobalt Pincer-NHC Complex

Highly regioselective hydroboration of unsymmetrical internal alkynes remains a significant challenge for synthesizing valuable alkenylboronate esters. Herein, we describe an easily synthesizable pincer NHC-based Co complex as a catalyst for the cis-α selective hydroboration of unactivated internal alkynes and the cis-β selective hydroboration of activated internal alkynes with pinacolborane. The reaction showcases high chemo-, regio-, and stereoselectivity, and the catalyst displays high efficiency and very low loading under base-free reaction conditions. The reaction scope was demonstrated by alkynes having a variety of functional groups. The mechanistic studies suggest a feasible Co-boryl intermediate to explain the unusual regioselectivity.

Synthesis of cobalt phosphide hybrid for simultaneous electrochemical detection of ascorbic acid, dopamine, and uric acid

Ascorbic acid (AA), dopamine (DA), and uric acid (UA) are important biomarkers for the clinical screening of diseases. However, the simultaneous determination of these three analytes is still challenging. Herein, we report a facile metal-organic framework (MOF)-derived method to synthesize a cobalt phosphide (Co2P) hybrid for the simultaneous electrochemical detection of AA, DA and UA. The introduction of highly dispersed Co2P nanoparticles onto a P, N-doped porous carbon matrix is responsible for providing abundant active sites and facilitating electron transfer, thereby contributing to the improved electrocatalytic performance of the hybrid. Well-resolved oxidation peaks and an enhanced current response for the simultaneous oxidation of AA, DA, and UA were achieved using a Co2P hybrid-modified screen-printed electrode (Co2P hybrid-SPE) with the differential pulse voltammetry (DPV) method. The detection limits for AA, DA, and UA in simultaneous detection were calculated as 17.80 μM, 0.018 μM, and 0.068 μM (S/N = 3), respectively. Furthermore, the feasibility of using Co2P hybrid-SPE for the simultaneous detection of AA, DA, and UA in real serum samples was also confirmed.

-CoOTe ( = S, Se, and P) with Oxygen/Tellurium Dual Vacancies and Banana Stem Fiber-Derived Carbon Fiber s Battery-Type Cathode and Anode Materials for Asymmetric Supercapacitor

In this work, we demonstrated the synthesis of anions (X = selenium (Se), sulfur (S), and phosphorus (P)) doped cobalt oxytelluride (X-CoOTe) with oxygen and tellurium dual vacancies using hydrothermal methods, followed by selenization, sulfurization, and phosphorization reactions. Especially, the Se-CoOTe-modified nickel foam (Se-CoOTe/NF) electrode delivered a higher specific capacity (752.95 C/g) and an extremely lower charge transfer resistance (0.87 Ω) than S-CoOTe/NF and P-CoOTe/NF due to the higher metallic conductivity of Se. Both oxygen and tellurium vacancies facilitate higher charge transfer conductivity, specific capacity, and stability. On the other hand, banana stem core fiber-derived activated carbon fiber (AC) with exfoliated carbon sheet, cracked surface, and corresponding high surface area boosts the excellent cycle stability up to 4000 cycles with capacitance retention of 100.29%. Thus, the asymmetric device (Se-CoOTe/NF//AC/NF) exhibited an extendable cell voltage (1.55 V), higher energy density (155.6 W h kg-1) at a power density (1356.2 W kg-1), and generous long-term stability (100% retention up to 10 000 cycles) in a liquid alkaline electrolyte. In the practicability test, the proposed asymmetric device mutually showed an increased operating voltage from 1.55 to 4.65 V for a three-series connection. In a three-series connection, a single white LED and an LED string glowed efficiently. This new finding will be very useful to develop tellurium-based chalcogenides and biowaste-derived carbon for energy storage applications.

Activation-Assisted High-Concentration Phosphorus-Doping to Enhance the Electrochemical Performance of Cobalt Carbonate Hydroxide Hydrate

P-doping into metal oxides has been demonstrated as a valid avenue to ameliorate electrochemical performance because it can tune the electronic structures and increase the active sites for an electrochemical reaction. However, it usually results in a low P-doping concentration via the commonly used gas phosphorization method. In this work, an activation-assisted P-doping strategy was explored to significantly raise the P-doping concentration in cobalt carbonate hydroxide hydrate (CCHH). The activation treatment increased active sites for electrochemical reaction and endowed the sample with a high P content in the subsequent gas phosphorization process, thereby greatly enhancing the conductivity of the sample. Therefore, the final CCHH-A-P electrode exhibited a high capacitance of 6.62 F cm^-2 at 5 mA cm^-2 and good cyclic stability. In addition, the CCHH-A-P//CC ASC with CCHH-A-P as the positive electrode and carbon cloth as the negative electrode provided a high energy density of 0.25 mWh cm^-2 at 4 mW cm^-2 as well as excellent cycling performance with capacitance retention of 91.2% after 20,000 cycles. Our work shows an effective strategy to acquire Co-based materials with high-concentration P-doping that holds great potential in boosting the electrochemical performance of electrode materials via P-doping technology.

Ultrasensitive Nonenzymatic Real-Time Hydrogen Peroxide Monitoring Using Gold Nanoparticle-Decorated Titanium Dioxide Nanotube Electrodes

An amperometric enzyme-free hydrogen peroxide (H₂O₂) sensor was developed by catalytically stabilizing active gold nanoparticles (Au NPs) of 4-5 nm on a porous titanium dioxide nanotube (TiO₂ NTs) electrode. The Au NPs were homogeneously distributed on anatase TiO₂ NTs with an outer diameter of ~102 nm, an inner diameter of ~60 nm, and a wall of thickness of ~40 nm. The cyclic voltammogram of the composite electrode showed a pair of redox peaks characterizing the electrocatalytic reduction of H₂O₂. The entrapping of Au NPs on TiO₂ NTs prevented aggregation and facilitated good electrical conductivity and electron transfer rate, thus generating a wide linear range, a low detection limit of ~104 nM, and high sensitivity of ~519 µA/mM, as well as excellent selectivity, reproducibility, repeatability, and stability over 60 days. Furthermore, excellent recovery and relative standard deviation (RSD) were achieved in real samples, which were tap water, milk, and Lactobacillus plantarum bacteria, thereby verifying the accuracy and potentiality of the developed nonenzymatic sensor.

Construction of shell-core Co2P/Cd0.9Zn0.1S photocatalyst by electrostatic attraction for enhancing H2 evolution

Solar energy-driven photocatalytic decomposition of water to produce H₂ is of great significance for promoting the development of clean energy. To improve the efficiency of H₂ production, a novel spherical Co₂P/Cd_0.9Zn_0.1S (Co₂P/CZS) composite with shell-core structure was successfully synthesized by electrostatic attraction. Under visible light irradiation, the optimal Co₂P/CZS achieves an excellent H₂ rate of 16.05 mmol h^-1 g^-1 in benzyl alcohol (PhCH₂OH) solution, with a quantum efficiency of 34.3% at 450 nm. The Co₂P thin layer coated on the CZS surface not only facilitates the photogenerated charge transfer from Co₂P to CZS under visible light illumination, but reduces the energy barrier of PhCH₂OH oxidation and H₂ evolution. The present results show that shell-core Co₂P/CZS composite may be one of promising catalyst to enhance the activity of H₂ evolution, which provides an important reference basis for new catalyst design and wide prospects for further application of metal sulfides.

Synthesis of Bimetallic Ni-Co Phosphide Nanosheets for Electrochemical Non-Enzymatic H2O2 Sensing

NiCoP nanosheets (NSs) were successfully synthesized using the hydrothermal and high-temperature phosphorization process. The obtained NiCoP NSs were immobilized on a glassy carbon electrode (GCE) and used to construct a novel sensing platform for electrochemical non-enzymatic H₂O₂ sensing. Physicochemical characteristics of NiCoP NSs were obtained by field-emission scanning electron microscopy (FESEM), field-emission transmission electron microscope (FETEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In addition, the electrochemical properties of NiCoP NSs were obtained by cyclic voltammetry (CV) and chronoamperometry (CA) towards the non-enzymatic detection of H₂O₂. FESEM and FETEM images provided a morphological insight (the unique nanosheets morphology of NiCoP) that could expose more active sites to promote mass/charge transport at the electrode/electrolyte interface. XRD and XPS results also confirmed the crystalline nature of the NiCoP nanosheets and the coexistence of multiple transitional metal oxidation states in NiCoP nanosheets. These unique physicochemical characteristics had a degree of contribution to ensuring enhancement in the electrochemical behavior. As a result, the synthesized NiCoP NSs composed of intercalated nanosheets, as well as the synergistic interaction between bimetallic Ni/Co and P atoms exhibited excellent electrocatalytical activity towards H₂O₂ electroreduction at neutral medium. As the results showed, the electrochemical sensing based on NiCoP NSs displayed a linear range of 0.05~4 mM, a sensitivity of 225.7 μA mM^-1 cm^-2, a limit of detection (LOD) of 1.190 μM, and good selectivity. It was concluded that NiCoP NSs-based electrochemical sensing might open new opportunities for future construction of H₂O₂ sensing platforms.

Hexamethylenetetramine induced multidimensional defects in Co2P nanosheets for efficient alkaline hydrogen evolution

Crystal engineering is an important way to improve the catalytic performance of transition-metal phosphides. In this work, we propose a strategy for constructing multi-dimensional defects induced by hexamethylenetetramine, which effectively introduces grain boundaries, N doping and P vacancies into Co₂P nanosheets, and improves the activity and stability of the catalyst. Due to the synergistic effect of the multi-dimensional defects, the Co₂P nanosheets exhibit excellent HER catalytic performance, especially at a large current density of 100 mA cm^-2 with an overpotential of only 159 mV. Under 1 M KOH electrolyte and current density of 10 mA cm^-2, the long-term test for 36 h shows that the catalyst maintains a very high stability.

Photoelectrochemical sensing and mechanism investigation of hydrogen peroxide using a pristine hematite nanoarrays

In this paper, a facile hydrothermal combined with subsequent two-step post-calcination method was used to fabricate hematite (α-Fe₂O₃) nanoarrays on fluorine-doped SnO₂ glass (FTO). The morphology, crystalline phase, optical property and surface chemical states of the fabricated α-Fe₂O₃ photoelectrode were characterized by scanning electron microscopy, X-ray diffraction, ultraviolet visible spectroscopy and X-ray photoelectron spectroscopy correspondingly. The α-Fe₂O₃ photoelectrode exhibits excellent photoelectrochemical (PEC) response toward hydrogen peroxide (H₂O₂) in aqueous solutions, with a low detection limit of 20 μM (S/N = 3) and wide linear range (0.01-0.09, 0.3-4, and 6-16 mM). Additionally, the α-Fe₂O₃ photoelectrode shows satisfying reproducibility, stability, selectivity and good feasibility for real samples. Mechanism analysis indicates, comparing with H₂O, H₂O₂ possesses much more fast reaction kinetics over α-Fe₂O₃ surface, thus the recombination of photogenerated charges are reduced, followed by much more photogenerated electrons are migrated to the counter electrode via external circuit. The insight on the enhanced photocurrent, which is corelative to the concentration of H₂O₂ in aqueous solution, will stimulate us to further optimize the surface structure of α-Fe₂O₃ to gain highly efficient α-Fe₂O₃ based sensors.

Amplification of Ferroptosis with Liposomal Nanoreactor Cooperates with Low-Toxic Doxorubicin Apoptosis for Enhanced Tumor Chemotherapy

Despite the remarkable tumor inhibition effect of doxorubicin (DOX), its cardiotoxicity severly limits the clinical dosage and further impairs the chemotherapy efficacy. To improve the biosafety and effectiveness of conventional...