Universal Fully Integrated Wearable Sensor Arrays for the Multiple Electrolyte and Metabolite Monitoring in Raw Sweat, Saliva, or Urine.

Fully integrated wearable sensors are capable of dynamically, directly, and independently tracking biomarkers in raw noninvasive biofluids without any other equipment or accessories by integrating the unique on-body monitoring feature with the special complete functional implementation attribute. Sweat, saliva, and urine are three important noninvasive biofluids, and changes in their biomarkers hold great potential for revealing physiological conditions. However, it is still a challenge to design single fully integrated wearable sensor arrays (FIWSAs) that are universally able to concurrently measure electrolytes and metabolites in three of the most common noninvasive biofluids including sweat, saliva, and urine. Here, we propose the first single universal FIWSAs for wirelessly, noninvasively, and simultaneously measuring various metabolites (i.e., uric acid) and electrolytes (i.e., Na+ and H+) in raw sweat, saliva, or urine under subjects' exercise by integrating the specifically designed microfluidic, sensing, and electronic modules in a seamless manner. We evaluate its utility for noninvasive gout management in healthy subjects and in gout patients through a purine-rich meal challenge and with a medicine-treatment control, respectively. Noninvasive monitoring of multiple electrolytes and metabolites in a variety of raw noninvasive biofluids via such single universal FIWSAs may enrich the understanding of the biomarkers' levels in the body and would also facilitate self-health management.

A Bifunctional Fully Integrated Wearable Tracker for Epidermal Sweat and Wound Exudate Multiple Biomarkers Monitoring.

Fully integrated wearable electronics that combine the extraordinary feature of incessant and on-body operation with the distinctive external equipment-free trait are the ultimate goal of modern wearables. Epidermal sweat and wound exudate, as two noninvasively accessible biofluids on/surrounding the skin, reflect underlying health conditions. However, the design of universal wearable sensors with the bifunctional capability to monitor both epidermal secretions is still a challenge. Here, a single bifunctional fully integrated wearable tracker for wirelessly, simultaneously, and dynamically in situ measuring multiple epidermal sweat or wound exudate biomarkers is propos. Considering the electrolytes (e.g., Na+ , K+ , and H+ ) and metabolites (e.g., uric acid (UA)) levels in sweat or wound exudate may correlate with health or wound conditions, the dynamic and skin-on tracking of the biomarkers of Na+ , K+ , pH, and UA levels in sweat under subjects' exercise and in wound exudate during subjects' wound healing are performed through the seamless integration of microfluidic, sensing, and electronic modules. Its applicability is evaluated for noninvasive hyperuricemia management in hyperuricemia/healthy subjects through a purine-rich intake test and for wound management in subjects' infected wounds through a control medical treatment.

Preparation of a novel Ni-MOF and porous graphene aerogel composite and application for simultaneous electrochemical determination of nitrochlorobenzene isomers with partial least squares.

Metal-organic framework Ni2(BDC)2(DABCO) (Ni-MOF)/porous graphene aerogel (PGA) composites were fabricated for the first time. The introduction of PGA enhances conductivity of Ni-MOF, prevents Ni-MOF from accumulating, reduces the size of Ni-MOF, and increases the pore size of composites, which improve the electrocatalytic activity of Ni-MOF@PGA-2. The prepared sensors based on Ni-MOF@PGA-2 composite show the highest catalytic current towards electroreduction of 2-nitrochlorobenzene (2-NCB), 3-nitrochlorobenzene (3-NCB), and 4-nitrochlorobenzene (4-NCB) at around - 0.61 V, - 0.56 V, and - 0.57 V (vs. Ag/AgCl) with respect to other sensors. The reaction mechanisms also are discussed. Under optimized experiment conditions, the Ni-MOF@PGA-2/GCE displays the widest linear range (6-1260, 4-980, and 2-1280 µM for 2-NCB, 3-NCB, and 4-NCB, respectively) for determination of individual nitrochlorobenzene isomers (NCBIs) compared to that of recent reports, and relatively low detection limit (0.093, 0.085, and 0.051 µM for 2-NCB, 3-NCB, and 4-NCB, respectively). More importantly, three NCBIs in the mixture were for the first time simultaneously determined by combining differential pulse voltammetry (DPV) based on Ni-MOF@PGA-2/GCE with partial least squares (PLS) chemometrics modeling method. The proposed method was evaluated towards the determination of NCBI mixtures in tap water and Jing lake water, and satisfactory recoveries were obtained. Graphical abstract.

A nanocomposite prepared from metal-free mesoporous carbon nanospheres and graphene oxide for voltammetric determination of doxorubicin.

A metal-free catalyst is described that consists of a composite that can be prepared from mesoporous carbon spheres (MCS) and graphene oxide (GO) under mild aqueous synthetic conditions. The reduced graphene oxide (rGO) sheets tend to aggregate, but due to the insertion of MCS, the aggregation is prevented. This leads to a larger surface area and more adsorption sites for the cancer drug doxorubicin (DOX). The π-interaction between DOX and rGO is also beneficial for the adsorption of DOX. A glassy carbon electrode (GCE) was modified with the composite and used to detect low levels of DOX, typically at a peak potential near -0.45 V (vs. Ag/AgCl). The modified GCE has a wide linear response range (10 nM - 10 µM), a low limit of detection (1.5 nM; at S/N = 3), excellent selectivity, long-term storage stability and reproducibility. It was applied to the determination of DOX in spiked serum where it gave reliable results. Graphical abstract Schematic representation of the preparation of mesoporous carbon spheres/reduced graphene oxide (MCS/rGO) sample, and the CV scan of doxorubicin (DOX) on MCS/rGO based nanoprode.

Correction to: Synthesis of a three-dimensional interconnected carbon nanorod aerogel from wax gourd for amperometric sensing.

The published version of this article, unfortunately, contains error. The authors regret that one typo was present in the first author name "Cuxing Xu" when it should be "Cuixing Xu".

Amperometric sensing of ascorbic acid by using a glassy carbon electrode modified with mesoporous carbon nanorods.

Mesoporous carbon nanorods (MCNRs) were prepared from honey as the carbon source and by using crab (Brachyuran) shells as the hard template. The unique nanostructure of the MCNRs with their uniform mesoporous size, abundant defective sites and numerous oxygen-functional groups was characterized by nitrogen adsorption-desorption isotherms, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Cyclic voltammograms of a glassy carbon electrode (GCE) modified with MCNRs revel a higher peak current density and lower peak potential (-0.03 V vs. Ag/AgCl) for ascorbic acid (AA) electrooxidation compared to a conventional GCE and a carbon nanotube-modified GCE. Figures of merit for this sensor include (a) a wide linear range (10-2770 µM), (b) high electrochemical sensitivity (216.91 µA mM-1 cm-2) and (c) a low detection limit (2.3 µM). These compare favorably to the respective data for a CNT-modified GCE (50-2150 µM, 5.20 µA mM-1 cm-2 and 26.8 µM) and a plain GCE (100-2000 µM, 0.58 µA mM-1 cm-2 and 54.6 µM). The modified GCE was successfully applied to the determination of AA in (spiked) real samples including an injection, soft drinks and fresh lemon juice. Therefore, the new sensor can be considered as an affordable tool for electrochemical sensing of AA in real samples. Graphical abstract Mesoporous carbon nanorods (MCNRs) were prepared by using honey as the carbon source and crab shells as the hard template. The MCNRs modified a glassy carbon electrode (MCNRs/GCE) was used for the ascorbic acid (AA) detection by amperometry.

Synthesis of a three-dimensional interconnected carbon nanorod aerogel from wax gourd for amperometric sensing.

The authors describe a method for synthesis of a three-dimensional (3D) interconnected carbon nanorod aerogel (3D-ICNA) starting from wax gourd (Benincasa hispida) which is a low-cost biomass. The 3D-ICNA possesses unique 3D interconnected and porous nanostructure, with abundant edge-plane-like defective sites, a large specific surface area (823 m2 g-1) and a large pore volume (0.12 cm3 g-1). This makes the material attractive in terms of electrochemical sensing. To validate the feasibility, the voltammetric response towards ferricyanide, hydrogen peroxide (H2O2), acetaminophen, ascorbic acid (AA), dopamine, uric acid and epinephrine was investigated by using a glassy carbon electrode (GCE) modified with 3D-ICNA. The modified GCE shows higher electron-transfer capacity than a conventional GCE. In addition, as an electrochemical sensor for AA or H2O2, the electrode exhibits better analytical performance with lower detection limit [3.5 µM for AA or 0.68 µM for H2O2 based on 3σ/m criterion (where σ is the standard deviation of the blank and m is the slope of the calibration plot)], wider linear range and higher sensitivity (0.14, 0.11 and 0.080 µA µM-1 cm-2 for AA or 0.24 and 0.20 µA µM-1 cm-2 for H2O2) compared to a plain GCE or a carbon nanotube-modified GCE. The modified GCE exhibits a large potential for the amperometric determination of AA or H2O2 in real samples. Graphical abstract By employing the biomass of wax gourd (Benincasa hispida) as the precursor, a three-dimensional interconnected carbon nanorod aerogel was prepared. It is shown to be a viable material for the construction of an advanced electrochemical sensor for H2O2 and ascorbic acid.

Ultrastable Polymolybdate-Based Metal-Organic Frameworks as Highly Active Electrocatalysts for Hydrogen Generation from Water.

Two novel polyoxometalate (POM)-based metal-organic frameworks (MOFs), [TBA]3[ε-PMo(V)8Mo(VI)4O36(OH)4Zn4][BTB]4/3·xGuest (NENU-500, BTB = benzene tribenzoate, TBA(+) = tetrabutylammonium ion) and [TBA]3[ε-PMo(V)8Mo(VI)4O37(OH)3Zn4][BPT] (NENU-501, BPT = [1,1'-biphenyl]-3,4',5-tricarboxylate), were isolated. In these compounds, the POM fragments serving as nodes were directly connected with organic ligands giving rise to three-dimensional (3D) open frameworks. The two anionic frameworks were balanced by TBA(+) ions residing inside the open channels. They exhibit not only good stability in air but also tolerance to acidic and basic media. Furthermore, they were employed as electrocatalysts for the hydrogen evolution reaction (HER) owing to the combination of the redox activity of a POM unit and the porosity of a MOF. Meanwhile, the HER activities of ε(trim)(4/3), NENU-5, and HKUST-1 were also studied for comparison. Remarkably, as a 3D hydrogen-evolving cathode operating in acidic electrolytes, NENU-500 exhibits the highest activity among all MOF materials. It shows an onset overpotential of 180 mV and a Tafel slope of 96 mV·dec(-1), and the catalytic current density can approach 10 mA·cm(-2) at an overpotential of 237 mV. Moreover, NENU-500 and NENU-501 maintain their electrocatalytic activities after 2000 cycles.

Novel bamboo leaf shaped CuO nanorod@hollow carbon fibers derived from plant biomass for efficient and nonenzymatic glucose detection.

The present paper reports on the preparation of novel bamboo leaf shaped CuO nanorod dispersed hollow carbon fibers (denoted as CuO NR@PCFs). Specially, the new-type hollow carbon fibers (containing abundant micro/meso/macropores and a large specific surface area) were prepared only by simple and fast pyrolysis of the natural product catkins without using any template or surfactant. Meanwhile, a facile method was used to prepare the bamboo leaf shaped CuO nanorod covered PCFs. Thanks to the abundant micro/meso/macropores, large specific surface area, and excellent electrical conduction efficiency of the PCF matrix, the as-prepared CuO NR@PCFs could also afford more catalytic sites, show more excellent reactant transport efficiency, and display more excellent electron transport rates compared with those for the pure CuO balls. Above all, these advantages will result in the excellent oxidation and detection efficiency of the CuO NR@PCF sample to glucose. Electrochemical measurements reveal that the CuO NR@PCF modified electrode can directly catalyze glucose oxidation and display an enhanced current response compared with the pure CuO balls (such as a response time within 4 s, wide linear ranges of 5 × 10(-3)-0.8 mM and 0.8-8.5 mM, good reproducibility, considerable stability, and excellent anti-interference to electroactive molecules and Cl(-)). The superior catalytic activity and selectivity make the CuO NR@PCF catalyst very promising for application in direct detection of glucose.

Recycling cobalt from spent lithium-ion batteries for designing the novel cobalt nitride followers: Towards efficient overall water splitting and advanced zinc-air batteries.

Although cobalt nitride (CoN)-based nanomaterials have been widely designed as advanced oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR) catalysts, the continuous consumption of lithium-ion batteries (LIBs) has led to a high price of cobalt metal. Therefore, in the future, recycling valuable Co elements from spent devices and boosting their service efficiency will inevitably promote the utilization of Co-based materials in water splitting and zinc-air batteries (ZABs). Herein, we realize the Co recycling from spent LIBs by a simple hydrometallurgy method. Under the assistance of hexamethylenetetramine and polystyrene spheres, after the hydrothermal and pyrolysis treatment in the NH3 atmosphere, the as-reclaimed cobalt oxalates were successfully transformed into novel three-dimensional (3D) CoN nanoflowers (denoted as CoN NFs). Benefiting from the unique 3D flower-like architectures, intrinsic high conductivity, large surface area, uniformly dispersed CoN nanoparticles, and the synergistic effect between Co3N and CoO phases, the 3D flower-like CoN NFs exhibited excellent OER catalytic activity. The performance was much better than commercial RuO2 in the 1.0 M KOH solution. Furthermore, the CoN NFs-based water splitting cell needed a voltage of 1.608 V to achieve the current density of 10 mA cm-2, which is even 16 mV smaller than that of Pt/C||RuO2 benchmark (1.624 V). Meanwhile, the CoN NFs-derived ZAB exhibited a high peak power density of 107.3 mW cm-2 (vs. 103.2 mW cm-2 of Pt/C-RuO2-based ZAB) and a low charge-discharge voltage gap (0.93 V vs. 1.43 V of Pt/C-RuO2-based ZAB). Due to the excellent structural and elemental stabilities, the corresponding water splitting cell and ZAB had outstanding durability. This work successfully explored an advanced industrial chain from recycling Co metal in spent devices to designing the high-efficiency HER/OER/ORR electrocatalysts for advanced water splitting devices and ZABs. This will further promote the value-added utilization of valuable Co metal in various energy storage or conversion devices.

Heterometallic MIL-125(Ti-Al) frameworks for electrochemical determination of ascorbic acid, dopamine and uric acid.

The detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) is not only of great significance in the areas of biomedicine and neurochemistry but also helpful in disease diagnosis and pathology research. Due to their diverse structures, designability, and large specific surface areas, metal-organic frameworks (MOFs) have recently caught considerable attention in the electrochemical field. Herein, a family of heterometallic MOFs with amino modification, MIL-125(Ti-Al)-xNH2 (x = 0%, 25%, 50%, 75%, and 100%), were synthesized and employed as electrochemical sensors for the detection of AA, DA, and UA. Among them, MIL-125(Ti-Al)-75%NH2 exhibited the most promising electrochemical behavior with 40% doping of carbon black in 0.1 M PBS (pH = 7.10), which displayed individual detection performance with wide linear detection ranges (1.0-6.5 mM for AA, 5-100 µM for DA and 5-120 µM for UA) and low limits of detection (0.215 mM for AA, 0.086 µM for DA, and 0.876 µM for UA, S/N = 3). Furthermore, the as-prepared MIL-125(Ti-Al)-75%NH2/GCE provided a promising platform for future application in real sample analysis, owing to its excellent anti-interference performance and good stability.

Preparation of copper oxide anchored on surfactant-functionalized macroporous carbon composite and its electrochemical applications.

Copper oxide nanoparticles were anchored on sodium dodecyl sulphate (SDS)-functionalized macroporous carbon by utilizing the supramolecular self-assembly of SDS acting as a soft template. The as-prepared composite provides new features of electrocatalytic activities and may hold great promise for the design of environmental sensors.

Ordered mesoporous boron-doped carbons as metal-free electrocatalysts for the oxygen reduction reaction in alkaline solution.

Ordered mesoporous boron-doped carbons (BOMCs) were prepared by co-impregnation and carbonization of sucrose and 4-hydroxyphenylboronic acid into SBA-15 silica template. Nitrogen sorption, small angle X-ray diffraction (XRD), and transmission electron microscopy (TEM) reveals that BOMCs possess highly ordered mesoporous structure, uniform pore size distribution, and high surface area. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that B atoms can be successfully doped into the framework of OMCs. Due to the desirable characteristics of BOMCs, BOMCs are highly active, cheap, and selective metal-free electrocatalysts for the oxygen reduction reaction (ORR) in alkaline solution. Although B content is a key factor in determining ORR activity, the ORR activity of BOMCs is also dependent on the surface area. The high surface area of BOMCs facilitates the exposure of the active sites for ORR. BOMCs may be further exploited as potentially efficient and inexpensive metal-free ORR catalysts with good long-term stability in alkaline solution.

Fabrication of manganese borate/iron carbide encapsulated in nitrogen and boron co-doped carbon nanowires as the accelerated alkaline full water splitting bi-functional electrocatalysts.

With high prices of precious metals (such as platinum, iridium, and ruthenium) and transition metals (such as cobalt and nickel), the design of high-efficiency and low-cost non-precious-metal-based catalysts using iron (Fe) and manganese (Mn) metals for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are critical for commercial applications of water splitting devices. In the study, without using any template or surfactant, we successfully designed novel cross-linked manganese borate (Mn3(BO3)2) and iron carbide (Fe3C) embedded into boron (B) and nitrogen (N) co-doped three-dimensional (3D) hierarchically meso/macroporous carbon nanowires (denoted as FexMny@BN-PCFs). Electrochemical test results showed that the HER and OER catalytic activities of Fe1Mn1@BN-PCFs were close to those of 20 wt% Pt/C and RuO2. For full water splitting, (-) Fe1Mn1@BN-PCFs||Fe1Mn1@BN-PCF (+) cell achieved a current density of 10 mA cm-2 at a cell voltage of 1.622 V, which was 14.2 mV larger than that of (-) 20 wt% Pt/C||RuO2 (+) benchmark. The synergistic effect of 3D hierarchically meso/macroporous architectures, excellent charge transport capacity, and abundant active centers (cross-linked Mn3(BO3)2/Fe3C@BNC, BC3, pyridinic-N, MNC, and graphitic-N) enhanced the water splitting catalytic activity of Fe1Mn1@BN-PCFs. The (-) Fe1Mn1@BN-PCFs||Fe1Mn1@BN-PCF (+) cell exhibited excellent stability owing to the superior structural and chemical stabilities of 3D hierarchically porous Fe1Mn1@BN-PCFs.

Synthesis of three-dimensional (3D) hierarchically porous iron-nickel nanoparticles encapsulated in boron and nitrogen-codoped porous carbon nanosheets for accelerated water splitting.

Designing two-dimensional (2D) porous carbon nanosheets is a promising strategy for enhancing the water-splitting activities of non-noble metal catalysts. In this study, we developed a novel method for synthesizing the novel three-dimensional (3D) hierarchically porous iron-nickel (FeNi) nanoparticles encapsulated in boron (B) and nitrogen (N)-codoped porous carbon nanosheets (denoted as FeNi@BNPCNS). Owing to the advantages of morphology and structure of B and N, 10.31 atom % of B/N active centers were successfully doped into the optimal FeNi@BNPCNS-800 nanosheets. FeNi@BNPCNS-800 exhibited better hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalytic activities than control catalysts in an alkaline solution. However, the HER and OER electrocatalytic activities of FeNi@BNPCNS-800 were slightly lower than 20 wt% Pt/C and RuO2. The FeNi@BNPCNS-800||FeNi@BNPCNS-800 electrolyzer achieved 10 mA cm-2 at 1.514 V, which was 73 mV lower than that of 20 wt% Pt/C||RuO2 electrolyzer (1.587 V). The perfect 3D honeycomb-like architectures, abundant mesopores/defects, and abundant electrocatalytic active sites were attributed to the outstanding water-splitting performances of FeNi@BNPCNS-800 nanosheets. This study provides an efficient strategy for the large-scale, rapid, and low-cost fabrication of 2D porous carbon nanosheets without using any template, surfactant, or expensive raw material, thus presenting a simple approach to design advanced non-noble metal electrocatalysts for water splitting.

Carboxyl induced ultrahigh defects and boron/nitrogen active centers in cobalt-embedded hierarchically porous carbon nanofibers: The stable oxygen reduction reaction catalysis in acid.

Transition metal-nitrogen-carbon (MNC) type catalysts have been considered a promising alternative to noble metals for oxygen reduction reaction (ORR) electrocatalysis. Nevertheless, poor stabilities of MNC catalysts in acidic solutions limit their commercialization. In this study, we design and synthesize novel three-dimensional (3D) cobalt (Co) nanoparticles encapsulated in ultrahigh content of boron (B) and nitrogen (N) -doped hierarchically porous carbon nanofibers (denoted as Co@BN-PCNFs) by carbonizing the 3D acetic acid/cobalt nitrate/4-hydroxybenzeneboronic acid/polyvinylpyrrolidone precursor networks woven using electrospinning method under a nitrogen atmosphere. The optimal Co@BN-PCNFs-900 catalyst has abundant micro/mesopores and numerous topological defects and exhibits the largest surface area. Under the synergistic effect of oxygen-containing acetic acid molecules and the electrospinning technology, 5.87 at.% of B and 5.91 at.% of N atoms were doped into carbon nanofibers. Specifically, B/N electrocatalytic active centers (including BC3, pyridinic-N/CoNC, pyrrolic-N, and graphitic-N) of approximately 8.70 at.% were successfully introduced into the skeletons of Co@BN-PCNFs-900. In 0.1 M KOH, the ORR onset potential (Eonset) and half-wave potential (E1/2) of Co@BN-PCNFs-900 were âˆ¼ 64 and âˆ¼ 63 mV, respectively, more positive than those of 20 wt% Pt/C. Additionally, in 0.5 M H2SO4, the ORR Eonset and E1/2 values of Co@BN-PCNFs-900 were only âˆ¼ 11 and âˆ¼ 7 mV, respectively, more negative than those of 20 wt% Pt/C. As the 3D hierarchically porous architectures, topological carbon edges, BC3, and partial NC/CoNC are relatively stable, the Co@BN-PCNFs-900 exhibits excellent stability toward ORR catalysis in both acidic and basic media. These favorable properties of Co@BN-PCNFs-900 nanofibers make them the best non-noble metal-based carbonaceous electrocatalysts for ORR in acidic electrolytes.

Laser-enabled flexible electrochemical sensor on finger for fast food security detection.

Today's rampant abuse of antibiotics and lean meat powder disturbs environment and threatens public human health. Therefore, fast in-site detection of antibiotics or lean meat powder residue could avoid potential risks. In this work, flexible graphene electrodes (FGE) were easily and facilely patterned and prepared by CO2 laser at room environment, which was coupled with a portable electrochemical analyzer for electronic signal transmission. Laser-enabled flexible electrochemical sensor on finger can be used for rapid real-time in-site electrochemical identification of chloramphenicol (CAP), clenbuterol (CLB) and ractopamine (RAC) in meat. The electrochemical response of CAP, CLB and RAC is investigated with the limit of detection of 2.70, 1.29 and 7.81 µM and the linear range of 10-200, 5-80 and 25-250 µM in phosphate buffer saline (PBS) pH 7.0, correspondingly. The minimum detection concentrations of CAP, CLB and RAC were 20, 10 and 30 µM, respectively, in actual samples of pork. And the minimum detection concentrations of CAP, CLB and RAC were 10, 5 and 25 µM in milk, respectively. Such an integrated sensing platform enriches application of sensors on finger in food security and provides information that prevents drug containments from entering food chain.

Single-Step and Room-Temperature Synthesis of Laser-Induced Pt/VC Nanocomposites as Effective Bifunctional Electrocatalysts for Hydrogen Evolution and Oxygen Evolution Reactions.

The development of cost-effective Pt-based electrocatalysts is of great scientific and industrial significance for improving the electrocatalytic activity of hydrogen evolution (HER) and oxygen evolution (OER) reactions for overall water splitting. In this work, unlike traditional furnace pyrolysis, we report the rapid and single-step room-temperature synthesis of Pt/VC nanocomposites with a three-dimensional (3D) network porous structure by laser irradiation technology. The resultant Pt-based composite (Pt/VC-2.84) could be applied to HER under different pH conditions. In particular, the content of Pt in Pt/VC-2.84 is only 2.84 wt %, which is far lower than that in the advanced HER electrocatalyst with the Pt content of 20 wt % (commercial 20 wt % Pt/C). In addition, Pt/VC-2.84 exhibits a boosted higher OER activity and stability than RuO2 in an alkaline medium. Most importantly, electrocatalytic results reflect that Pt/VC-2.84 reveals superior activity and stability toward overall water splitting.

Laser-assisted coupling of nitrogen-doped carbon-coated molybdenum/molybdenum dioxide rods for efficient pH-universal hydrogen evolution electrocatalysis.

Herein, a simple and fast laser-assisted coupling method is used for preparation of rod-like carbon-coated Mo/MoO2 hybrids at room temperature and air environment. Under high energy of laser and reductive atmosphere caused by precursor decomposition, Mo-polydopamine complex-wrapped MoO3 rods are quickly converted into nitrogen-doped carbon-coated Mo/MoO2 rods. Carbon-coated Mo/MoO2 exhibits high surface area, uniform metal dispersion and appealing hydrogen evolution reaction (HER) catalytic performance in a wide pH range. Carbon-coated Mo/MoO2 shows overpotential of 134, 108 and 164 mV to deliver current density of 10 mA cm-2 under alkaline, acidic and neutral solution, respectively. Theoretical calculation demonstrates that combination of Mo and MoO2 into Mo/MoO2 composite favors the dissociation of water and adsorption of hydrogen. This study not only provides a high-efficiency strategy for preparation of electrocatalysts but also give guidance for development of hybrid electrocatalysts for HER.

Morphological modulation of iron carbide embedded nitrogen-doped hierarchically porous carbon by manganese doping as highly efficient bifunctional electrocatalysts for overall water splitting.

In the development of water splitting, the sluggish electrocatalytic kinetics of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have restricted their energy conversion efficiencies. Along with the continuous rise in the prices of noble metals and transition metals (such as cobalt and nickel), constructing high-efficiency HER/OER catalysts based on low cost transition metals, such as iron and manganese, is becoming more meaningful in developing industrialized water splitting devices. In this paper, in the absence of a template or active agent, three-dimensional, hierarchically porous FexMny nanoparticles (NPs) were embedded and nitrogen-doped carbon materials (denoted as FexMny@NC; x:y, representing the molar ratio of Fe:Mn) were successfully prepared via pyrolysis of corresponding precursors containing different metallic salt components. Various morphological, structural, and chemical characterization analysis demonstrate that at an Fe:Mn molar ratio of 3:1, the optimal Fe3Mn1@NC material shows high graphitization degree, rich mesoporous structures, a large surface area, and abundant carbon defects/edges, which promote the uniform dispersion of pyridinic-N (pyridinic-N-metal), graphitic-N, carbon oxygen bonds (CO), manganese oxide (MnO) nanocrystals, and Fe3C NPs-embedded, N-doped carbon sheet (Fe3C@NC) active sites. In alkaline conditions, the HER onset potentials (Eonset) and potentials recorded at 10 mA cm-2 (E10) of the optimal Fe3Mn1@NC are just 84.8 and 156 mV more negative than those of 20 wt% platinum carbon (Pt/C). Meanwhile, the OER Eonset and E10 values of the optimal Fe3Mn1@NC are just 8 and 18.7 mV more positive than those of RuO2. Furthermore, optimized Fe3Mn1@NC catalysts were assembled into a water splitting cell, where the catalytic current density achieves 10 mA cm-2 at a low voltage of 1.6287 V (with superior catalytic stability), which is just 24.9 mV higher than that of the (-) 20 wt% Pt/C||RuO2 (+) benchmark (1.6038 V) under the same conditions. This work describes the regulating efficiency of Mn toward growing mesopores and opens new possibilities for the development of novel carbonaceous catalysts with excellent hydroxide catalytic efficiencies based on low cost Mn/Fe elements.