NaBH4 Oxidation Research Articles

Investigation Towards the Asymmetric CBS‐Catalysed Reduction of Aryl Methyl Ketones with Electrochemically in Situ Generated BH3

AbstractThe aim of this investigation was to explore the possibility to perform an asymmetric reduction, utilising a CBS‐type catalyst, of prochiral aryl methyl ketones under electrochemical conditions to generate the needed BH3 upon oxidation of NaBH4 with in situ generated I2 in the anode compartment. Therefore, various electrochemical parameters were optimised to conduct the desired formation of the chiral secondary alcohols in high to quantitative yields with a high stereochemical induction, although the catalyst loading had to be chosen relatively high to concur with the racemic reduction of the ketones by the electrogenerated BH3.

An introductory review on advanced multifunctional materials

This review summarizes the applications of some of the advanced materials. It included the synthesis of several nanoparticles such as metal oxide nanoparticles (e.g., Fe3O4, ZnO, ZrOSO4, MoO3-x, CuO, AgFeO2, Co3O4, CeO2, SiO2, and CuFeO2); metal hydroxide nanosheets (e.g., Zn5(OH)8(NO3)2·2H2O, Zn(OH)(NO3)·H2O, and Zn5(OH)8(NO3)2); metallic nanoparticles (Ag, Au, Pd, and Pt); carbon-based nanomaterials (graphene, graphene oxide (GO), graphitic carbon nitride (g-C3N4), and carbon dots (CDs)); biopolymers (cellulose, nanocellulose, TEMPO-oxidized cellulose nanofibers (TOCNFs), and chitosan); organic polymers (e.g. covalent-organic frameworks (COFs)); and hybrid materials (e.g. metal-organic frameworks (MOFs)). Most of these materials were applied in several fields such as environmental-based technologies (e.g., water remediation, air purification, gas storage), energy (production of hydrogen, dimethyl ether, solar cells, and supercapacitors), and biomedical sectors (sensing, biosensing, cancer therapy, and drug delivery). They can be used as efficient adsorbents and catalysts to remove emerging contaminants e.g., inorganic (i.e., heavy metals) and organic (e.g., dyes, antibiotics, pesticides, and oils in water via adsorption. They can be also used as catalysts for catalytic degradation reactions such as redox reactions of pollutants. They can be used as filters for air purification by capturing carbon dioxide (CO2) and volatile organic compounds (VOCs). They can be used for hydrogen production via water splitting, alcohol oxidation, and hydrolysis of NaBH4. Nanomedicine for some of these materials was also included being an effective agent as an antibacterial, nanocarrier for drug delivery, and probe for biosensing.

Au-Pt bimetallic nanoparticles anchored on conducting polymer: An effective electrocatalyst for direct electrooxidation of sodium borohydride in alkaline solution

This work proposes Au-Pt nanoparticles decorated poly(p-aminophenol) (PAP) film on a glassy carbon electrode for direct electrochemical oxidation of sodium borohydride. The Au-Pt bimetallic surfaces were prepared with two electrodeposition procedures which are the simultaneous electro-deposition (1-Au-Pt/PAP/GCE) and the successive electro-deposition (2-Au-Pt/PAP/GCE) procedures. The catalysts were used for the investigation of borohydride electrochemical oxidation and compared catalytic activities by CV, RDEs and chronoamperometric techniques. AFM, SEM, XPS, XRD and CV were used to identify of the structural and morphological properties of the developed modified surfaces. The results of electrochemical measurements indicated that simultaneous electro-deposition of Au-Pt to the polymer structure significantly shifted negative oxidation potential and increases the current density of borohydride electrochemical oxidation.The exchange electron number of 1-Au-Pt/PAP/GC and 2-Au-Pt/PAP/GC electrodes were calculated as 7.8 and 6.7, respectively. This approves the strong tendency of the 1-Au-Pt/PAP catalyst toward effective direct electrochemical oxidation of NaBH4 in an alkaline medium.

3D Structured Pt(Cu-Ni)/Ti Catalysts for the Oxidation of Sodium Borohydride

Currently, one of the renewable energy sources is fuel cells, namely chemical energy is directly converted into electricity. Designing new or enhancing the existing fuel cells, much attention is devoted to the search of new effective catalysts, which would allow increasing the effectiveness of fuel cells and creating the background for designing new technologies for catalysts formation.The aim of the work is to form efficient and inexpensive nanostructured catalysts by electroplating 3D structure metal copper-nickel (Cu-Ni) foams on titanium (Ti) surface and decorating them with low amounts of platinum nanoparticles (PtNP) for the electrooxidation of sodium borohydride (NaBH4). The Cu-Ni foam was prepared by electrochemical deposition (I deposition=1.5 Acm-2, t deposition= 3,6 and 9 min) on Ti surface. The electrolyte contained 0.5 M Ni2+ ions, and the concentrations of Cu2+ ions ranged from 0.01 to 0.02 M.PtNP particles were deposited on Cu-Ni foam (noted (Pt(Cu-Ni)/Ti)) by immersion of Cu-Ni foam into 1 mM H2PtCl6 solution at 25 °C for 1 minute. The morphology and composition of the prepared catalysts were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The electrocatalytic activity of the 3D catalysts was evaluated towards the oxidation of borohydride by cyclic voltammetry method in 0.05 M NaBH4 solution in an alkaline media in the potential range from -1.2 to 0.6 V (vs. Ag/AgCl) and with an electrode potential scan rate of 10 mVs-1.The study showed that the prepared 3D Cu-Ni foam and Pt(Cu-Ni)/Ti have good electrochemical stability in alkaline NaBH4 solution. It was also observed that immersion of Cu-Ni foam in a platinum-containing solution for 1 min increased the electrocatalytic activity of the prepared Pt(Cu-Ni)/Ti catalysts for NaBH4 oxidation compared to Cu-Ni foam. Acknowledgment This project has received funding from European Social Fund (project No 09.3.3-LMT-K-712-19-0138) under a grant agreement with the Research Council of Lithuania (LMTLT).

Solvent Effects on Fluorescence Properties of Carbon Dots: Implications for Multicolor Imaging.

Carbon dots (CDs) are synthesized by the solvothermal method with four kinds of solvents including water, dimethylformamide (DMF), ethanol, and acetic acid (AA). The aqueous solutions of the above CDs emit multiple colors of blue (470 nm), green (500 nm), yellow (539 nm), and orange (595 nm). The structures, sizes, and chemical composition of the CDs are characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). The optical properties of multicolored CDs are analyzed by UV–vis absorption and photoluminescence (PL) spectra. It has been revealed that DMF is the key solvent to synthesized CDs for the red shift of fluorescence emission, which could be enhanced by adding an AA solvent. The structures of functional groups such as the contents of graphitic N in carbon cores and oxygen-containing functional groups on the surface of CDs are affected by these four solvents. According to the oxidation and selective reduction of NaBH4, the implication for multicolor imaging has been discussed based on the COOH, C–O–C, and C=O functional groups.

The microstructural refinement and performance improvement of a nanoporous Ag/CeO2 catalyst for NaBH4 oxidation

In this paper, Cu and Ce were added to melt-spun Al–Ag precursor alloys to refine the microstructures of nanoporous Ag and Ag/CeO2 composite catalysts for NaBH4 oxidation. After the precursor alloys were dealloyed in 20% NaOH, calcined in air and corroded again in 50% NaOH, Ag2Al in the precursor alloys was completely removed, and refined nanoporous Ag could be obtained; from this process, the finest microstructures were exhibited by Al84Ag8Cu8. When more than 0.3% Ce was added to the Al84Ag8Cu8 ribbons, a refined nanoporous Ag material that consisted of CeO2 nanorods interspersed between Ag ligaments was obtained. Electrochemical measurements indicated that the catalytic properties were clearly increased due to the Cu addition to the Al–Ag alloy. After Ce was added to the Al84Ag8Cu8 ribbons, the catalytic properties of the resulting material were further improved. In regard to melt-spun Al84Ag8Cu8Ce0.5, the obtained nanoporous Ag/CeO2 presented the best properties, and its current density was 2.5 times that of Al84Ag8Cu8, 3.1 times that of Al90Ag8Cu2 and 2.3 times that of Ag/Ce from the Al79Ag15Ce6 precursor alloy without Cu. It was believed that the core–shell structure composed of Ag and Cu-rich phases formed during dealloying could limit the diffusion of Ag and prevent the coarsening of Ag ligaments. Thus, the refined microstructures could provide a large specific surface or additional active sites for the catalytic reaction. Strong interactions resulted from the many interfaces between the Ag ligaments and interspersed CeO2 nanorods, and the more effective utilization of Ag was due to the decomposition of Ag2Al; this result was the key reason for the clear improvement in catalytic performance.

Investigation of stability of gold nanoparticles modified zinc–cobalt coating in an alkaline sodium borohydride solution

The electrochemical stability and durability of ZnCo alloy thin layers deposited on the titanium surface (denoted as ZnCo/Ti) and those modified by small amounts of Au nanoparticles (denoted as AuZnCo/Ti) prepared via the electrochemical metal deposition technique and a simple galvanic displacement have been investigated in alkaline sodium borohydride (NaBH4) solutions. The physical properties of the fabricated AuZnCo/Ti catalysts have been examined using field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX) and inductively coupled plasma optical emission spectroscopy (ICP-OES). The electrocatalytic activity of the ZnCo/Ti and AuZnCo/Ti catalysts toward the oxidation of NaBH4 has been evaluated in an alkaline medium using cyclic voltammetry (CV) and chronoamperometry (CA), whereas the catalytic efficiency of the catalysts for the hydrolysis reaction of NaBH4 has been also examined by measuring the amount of generated hydrogen via the classic water-displacement method. It has been determined that the modification of the ZnCo alloy coating by Au nanoparticles apparently improves not only the morphology and structure of the catalyst, but also the activity and stability of the one for the oxidation of NaBH4 in an alkaline medium as compared to those of ZnCo/Ti and bare Au. The AuZnCo/Ti catalysts that have Au loadings of 63 and 306 µg cm–2 give ca. 12 and 11, respectively, times higher NaBH4 oxidation current densities as compared to those of the bare Au catalyst. Moreover, the AuZnCo/Ti catalysts catalyze the hydrolysis reaction of NaBH4 in alkaline solutions.

Solvothermal synthesis of Pd10–Ni45–Co45/rGO composites as novel electrocatalysts for enhancement of the performance of DBFC

In this research, three Pd decorated Ni and Co catalyst nanoparticle were synthesized on reduced graphene oxide (rGO) supports are synthesized through a facile solvothermal procedure. Borohydride oxidation reaction (BOR) activity and performance of prepared electrocatalysts respect to NaBH4 oxidation is evaluated by various electrochemical techniques in the three-electrode and the fuel cell configuration. Among the prepared catalysts, Pd10–Ni45–Co45/rGO exhibits the highest BOR activity. The cyclic voltammograms showed that the measured current at 0.5 V for the electrode of Pd10–Ni45–Co45/rGO is as much as 108 mA cm−2 higher than Pd10–Ni90/rGO and 185 mA cm−2 higher than Pd10Co90/rGO. X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectra were employed to study the morphology and crystal structure of the prepared catalyst. The results of DBFC test show that the Pd10–Ni45–Co45/rGO nanoparticles as anodic catalyst, enhanced power density to 50.4 mW cm−2 which is 10.5% and 45.2% higher than power density of DBFCs with Pd10–Ni90/rGO (45.6 mW cm−2) and Pd10Co90/rGO (34.7 mW cm−2) anode catalysts, respectively. These results indicate that the competency of operating procedure for assembling nickel alloys electrodes can improve the activity of the prepared catalysts for BOR considerably.

(Invited) Efficient pH-Gradient-Enabled Microscale Bipolar Interfaces in High Performance Direct Borohydride Fuel Cells

Electrochemical energy conversion devices usually operate at uniform pH or over a narrow pH range. The uniform pH environment of these devices frequently hampers the facility of one of the half-cell reactions. In proton exchange membrane fuel cells (PEMFCs)/ proton exchange membrane water electrolyzers (PEMWEs), where both the anode and cathode operate at acidic pH, the H2 oxidation/evolution reaction is quite facile while the O2 reduction/evolution reaction is sluggish. In anion exchange membrane fuel cells (AEMFCs)/ anion exchange membrane water electrolyzers (AEMWEs), the converse is true. Moreover, the chemical stability of some reactants depends strongly on the pH. Direct borohydride fuel cells (DBFCs), operating with NaBH4 as a fuel and H2O2 as the oxidant have attracted a lot of attention due to their high theoretical cell voltages and tactical advantages, particularly for defense-related applications. DBFCs have a high energy density of 9.3 kWh kg-1 and specific capacity of 5.67 kAh kg-1 based on NaBH4 oxidation in alkaline media [1], although the practical energy density will be lowered upon accounting for the added weight of KOH solution required to stabilise NaBH4. Using liquid hydrogen peroxide as the oxidant, the DBFC is a safe and attractive low temperature power source for unmanned underwater vehicles (UUVs) as they exhibit excellent energy and power density, are safe, given the high flash point of NaBH4, and do not release any gaseous effluents, enabling operation at neutral buoyancy [2]. One challenge for this system is the separation between the anolyte fuel (1.5M NaBH4 in 3M KOH) and catholyte oxidant streams (15% H2O2 in 1.5M H2SO4), while another is the high instability of NaBH4 in acidic or even neutral pH [3]. Herein, a pH-gradient-enabled microscale bipolar interface (PMBI) is demonstrated for maintaining pH control of the anolyte and catholyte compartments of the fuel cell. The PMBI employed to separate anolyte and catholyte was based on an anion exchange membrane (AEM) interface in conjunction with a cation exchange membrane (Nafion®) separator. The DBFC with the PMBI yielded a current density of 330 mA/cm2 at 1.5 V and a promising peak power density of 630 mW cm-2 at 1 V in a 25-cm2 active area cell [4]. Using a recessed planar electrode (RPE) in conjunction with TEM, we show that the PMBI maintained a sharp local pH gradient (0.82 pH units/nm on average) at the electrocatalytic reaction site.

Formation of nanoporous Cu-Ag by dealloying Mg-Cu-Y-Ag amorphous alloys and its electrocatalyst oxidation property

The supersaturated Cu-Ag bimetallic nanoporous structure has been fabricated by dealloying of Mg65Cu25-xY10Agx (x = 0, 2, 4, 8) amorphous alloys and its electrocatalytic property for sodium borohydride (NaBH4) oxidation has been evaluated. In order to increase solid solubility of Ag into Cu, the dealloying process is proceeded in higher concentration sulfuric acid aqueous solution for shorter immersion time. When Mg65Cu25-xY10Agx amorphous alloys are dealloyed in 1.0 M solution for 30 s, the Cu-Ag bimetallic nanoporous structure in the form of solid solution is successfully obtained due to extended solid solubility in nm scale grain structure. Electrochemical oxidation of NaBH4 at Cu-(Ag) electrodes is studied in a mixture solution of 2.0 M NaOH and 0.1 M NaBH4. The electrocatalytic property of nanoporous Cu-Ag bimetallic electrodes is higher than that of Cu monometallic electrode. The electrode dealloyed from Mg65Cu21Y10Ag4 amorphous alloy exhibits the highest electrocatalytic property.

Surfactant‐Assisted Electrodeposition of Nickel Nanostructures and Their Electrocatalytic Activities Toward Oxidation of Sodium Borohydride, Ethanol, and Methanol

AbstractDifferent Ni nanostructures were electrodeposited from the Watts bath in the presence of different concentrations of sodium dodecyl sulfate (SDS) using the pulse reverse current technique on the copper substrate. The concentration of SDS was lower than the critical micelle concentration (CMC), equal to CMC and higher than CMC for electrodeposition of Ni‐1, Ni‐2, and Ni‐3 samples respectively. The electrodeposited samples were characterized by X‐ray diffraction (XRD), atomic force microscopy (AFM), and field emission‐scanning electron microscopy (FE‐SEM) techniques. The electrocatalytic activity of samples for oxidation of sodium borohydride, ethanol, and methanol was investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). For borohydride oxidation, one oxidation peak, as well as one semicircle, observed respectively in the cyclic voltammograms and Nyquist diagrams confirmed that only one reaction happened on the surface of samples. It was observed that at high overpotentials, Ni‐1 sample was more reactive for NaBH4 oxidation compared to the Ni‐2 and Ni‐3 samples.

Enhancement of output power density and performance of direct borohydride-hydrogen peroxide fuel cell using Ni-Pd core-shell nanoparticles on polymeric composite supports (rGO-PANI) as novel electrocatalysts

In this research work, Ni-Pd nanoparticles with core-shell structure (CNi-SPd) were synthesized on different catalyst supports such as reduced graphene oxide (rGO), pure polyaniline (PANI) and polymeric composites of rGO with PANI (rGO-PANI) for the first time. In polymeric composite supports, the ratio of rGO to PANI was altered (0.36, 0.14 and 0.11). That way, after chemical reduction of graphene oxide to rGO with sodium borohydride, different polymeric composite supports of rGO-PANI were prepared by chemical oxidation of different amounts of aniline monomer with ammonium persulfate (APS) in rGO dispersions and named as rGO-PANI1 (rGP1), rGO-PANI2 (rGP2) and rGO-PANI3 (rGP3). X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), fourier transform infrared (FT-IR) spectra, inductively coupled plasma mass spectrometry (ICP-MS) analysis and X-ray photoelectron spectrometer (XPS) were employed to study the morphology and crystal structure of the novel nanostructures. Catalytic behavior of the catalysts respect to NaBH4 oxidation was evaluated in half-cell configuration and in direct borohydride-hydrogen peroxide fuel cell. The cyclic voltammetry results showed that CNi-SPd/rGP1 has the highest borohydride oxidation current density (42678 A. g−1) respect to CNi-SPd/PANI (17072 A. g−1), CNi-SPd/rGO (39085 A. g−1), CNi-SPd/rGP2 (32260 A. g−1) and CNi-SPd/rGP3 (24954 A. g−1). As well as, the single fuel cell studies indicated that with CNi-SPd/rGP1 as anodic electrocatalyst, power density (339.10 mW.cm-2) was enhanced as 64.54% and 8.52% in comparison with CNi-SPd/PANI (120.23 mW.cm-2) and CNi-SPd/rGO (310.20 mW.cm-2), respectively. Theses consequences imply that the rGP1 polymeric composite with the ratio of rGO/PANI = 0.36 is a suitable support substance that can improves the electroactivity for borohydride oxidation considerably.

A novel electrode of ternary CuNiPd nanoneedles decorated Ni foam and its catalytic activity toward NaBH4 electrooxidation

Facile hydrothermal method and galvanic replacement are employed to synthesize an electrode of ternary CuNiPd nanoneedles decorated Ni foam toward NaBH4 electrooxidation. In the whole preparation, traditional polymer binders are avoided which efficiently lowers the electrode cost. X-ray diffraction, scanning electron microscopy and transmission electron microscopy are conducted to study the phase composition and morphology of CuNiPd nanoneedles. The unique needle-like structure of the as-prepared electrode allows electrolyte to fully contact with electrode surface which is beneficial to improve the catalytic activity. Besides, the electrochemical performance is tested through chronoamperometry and cyclic voltammetry in a traditional three-electrode system. In 2 mol L−1 NaOH and 0.3 mol L−1 NaBH4, a current density of 710 mA cm−2 at 0 V on the CuNiPd nanoneedles decorated Ni foam electrode is achieved which reveals a desired catalytic property for NaBH4 oxidation. In addition, the activation energy and number of exchange electrons of NaBH4 oxidation on CuNiPd nanoneedles decorated Ni foam electrode are 18.42 kJ mol−1 and 4.9. The excellent catalytic activity is a result of the synergy effect of Cu, Ni and Pd which makes the as-prepared electrode to be an alternative choice for direct sodium borohydride fuel cell.

DNA-Walker-Induced Allosteric Switch for Tandem Signal Amplification with Palladium Nanoparticles/Metal-Organic Framework Tags in Electrochemical Biosensing.

A DNA walker as a new molecular machine can walk on defined tracks to directly generate signal indicators in biosensing and biomedical applications. In this work, a tandem signal amplification strategy was developed on the basis of the DNA-walker-induced conformation switch for bridging palladium nanoparticles/metal-organic framework tags in ultrasensitive electrochemical DNA biosensing. The signal tags were synthesized by in situ reduction of Pd nanocrystals on porphyrinic metal-organic frameworks (PCN-224), followed by conjugation with streptavidin (SA). The as-prepared Pd/PCN-224-SA tag could electrocatalyze the oxidation of NaBH4 with high efficiency for signal readout. The presence of target DNA released swing arms that were each silenced by a blocker, and then the activated swing arms could hybridize with hairpin DNA. The movement of swing arms was powered by enzymatic cleavage of conjugated oligonucleotides, inducing the allosteric switch from hairpin to SA aptamer. Therefore, Pd/PCN-224-SA tags were brought onto the electrode surface via SA-aptamer biorecognition to generate the enhanced electrochemical signal. The DNA walker-based electrochemical biosensor demonstrated good performance such as 6 orders of magnitude linear range, femtomolar detection limit, and single mismatch differentiation ability. Moreover, the feasibility of the biosensor was identified in serum matrixes. The tandem signal amplification of metal-organic frameworks and DNA walkers provided a new avenue in trace electrochemical biosensing.

THE INVESTIGATION OF THE ELECTROOXIDATION OF SODIUM BOROHYDRIDE ON VARIOUS METAL ELECTRODES IN AQUEOUS BASIC SOLUTIONS

This study is related to the electrochemical oxidation of NaBH4 on Au, Pt, Pd and Ni electrodes by the use of cyclic and square wave voltammetry. The most effective metal for the oxidation of sodium borohydride was found to be Au. Pt and Pd electrodes also showed certain activity while Ni was not effective. The compound was observed to give two consecutive oxidation steps with 6 and 2 electron transfers. The experiments conducted while keeping the potential at −0.8V showed that the resulting compound is adsorbed upon the electrode surface and gradually decrease its catalytic activity.

Bipolar Polymer Electrolyte Interfaces As Separators for High Performance Direct Borohydride Fuel Cells

Direct borohydride fuel cells (DBFCs), operating with NaBH4 as a fuel and H2O2 as the oxidant have attracted a lot of attention due to their high theoretical cell voltages and tactical advantages, particularly for defense-related applications. DBFCs have a high energy density of 9.3 kWh kg-1 and specific capacity of 5.67 kAh kg-1 based on NaBH4 oxidation in alkaline media [1]. Using liquid hydrogen peroxide as the oxidant, the DBFC is a safe and attractive low temperature power source for unmanned underwater vehicles (UUVs) as they exhibit excellent energy and power density, are safe, given the high flash point of NaBH4, and do not release any gaseous effluents, enabling operation at neutral buoyancy[2]. One challenge for this system is the separation between the anolyte fuel (1.5M NaBH4 in 3M KOH) and catholyte oxidant streams (15% H2O2 in 1.5M H2SO4), while another is the high instability of NaBH4 in acidic or even neutral pH. Herein, a bipolar interface membrane electrode assembly is demonstrated for maintaining pH control of the anolyte and catholyte compartments of the fuel cell. The bipolar interface employed to separate anolyte and catholyte was based on an anion exchange membrane (AEM) interface in conjunction with a cation exchange membrane (Nafion®) separator. Studies of ion-containing block copolymers have provided clear evidence that the phase separation between hydrophilic and hydrophobic phases can produce materials with excellent ionic conductivity [3, 4]. The DBFC with the bipolar interfaces yielded a promising peak power density of 300 mW cm-2 in a 5-cm2 active area cell. Different operating conditions such as catalyst loading, operation temperature, flow rate and thickness of separator were investigated. The bipolar junction offers improved performance in the DBFC when compared with the use of a typical AEM or PEM configuration in the MEA.

Synthesis and investigation of a high-activity catalyst: Au nanoparticles modified metalic Ti microrods for NaBH4 electrooxidation

A novel catalyst electrode of Au nanoparticles modified Ti microrods is synthesized through a route of hydrothermal etching and electrodeposition. As substrate, the metallic Ti microrods are in-situ etched from the Ti plate using hydrochloric acid as an etching reagent. After that, Au is prepared on the metallic Ti microrods in a form of nanoparticle by electrodeposition. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) are conducted to investigate the structure and phase composition of the Au nanoparticles modified Ti microrods (Au/Ti MRs) electrode. Besides, the electrocatalytic property of the Au/Ti MRs electrode for NaBH4 oxidation is explored through chronoamperometry (CA) and cyclic voltammetry (CV). In alkaline solution, the Au/Ti MRs electrode displays excellent electrocatalytic property and good stability. At 0 V, there is a current density of 12.12 mA cm−2 on the as-prepared electrode in 2 mol L−1 NaOH and 0.1 mol L−1 NaBH4 that is twice as the current density on Au nanoparticles modified Ti plate electrode demonstrating huge potential for application in direct borohydride fuel cell.

Ni-Co nanoparticles immobilized on a 3D Ni foam template as a highly efficient catalyst for borohydride electrooxidation in alkaline medium

Proton exchange membrane (PEM) fuel cells have drawn a great deal of attention due to the rapidly growing energy consumption. Recently, Ni- and Co-based materials have been considered as promising electorcatalysts owing to their multi-functionality. In this work, Ni and Co nanoparticles are directly immobilized on a three-dimensional Ni foam substrate (Ni-Co/NF) without any conductive agents or polymer binder by a facile ion implantation method. The structure and morphology of the Ni-Co/NF electrode were characterized by scanning electron microscopy, powder X-ray diffraction, and X-ray photoelectron spectroscopy. The performance of the Ni-Co/NF electrode in the electrochemical oxidation of NaBH4 is investigated by cyclic voltammetry and chronoamperometry. The Ni-Co/NF electrode exhibited excellent electrocatalytic activity and good stability during electrochemical reactions. These properties are attributed to the 3D porous structure of the Ni foam and the synergistic effect of Ni and Co nanoparticles. The enhanced electrocatalytic performance in NaBH4 electrooxidation compared with either Ni or Co nanoparticles alone suggests that the Ni-Co/NF is promising for fuel cell applications.

Proximity hybridization-regulated catalytic DNA hairpin assembly for electrochemical immunoassay based on in situ DNA template-synthesized Pd nanoparticles

Novel hybridization proximity-regulated catalytic DNA hairpin assembly strategy has been proposed for electrochemical immunoassay based on in situ DNA template-synthesized Pd nanoparticles as signal label. The DNA template-synthesized Pd nanoparticles were characterized with atomic force microscopic and X-ray photoelectron spectroscopy. The highly efficient electrocatalysis by DNA template synthesized Pd nanoparticles for NaBH4 oxidation produced an intense detection signal. The label-free electrochemical method achieved the detection of carcinoembryonic antigen (CEA) with a linear range from 10−15 to 10−11 g mL−1 and a detection limit of 0.43 × 10−15 g mL−1. Through introducing a supersandwich reaction to increase the DNA length, the electrochemical signal was further amplified, leading to a detection limit of 0.52 × 10−16 g mL−1. And it rendered satisfactory analytical performance for the determination of CEA in serum samples. Furthermore, it exhibited good reproducibility and stability; meanwhile, it also showed excellent specificity due to the specific recognition of antigen by antibody. Therefore, the DNA template synthesized Pd nanoparticles based signal amplification approach has great potential in clinical applications and is also suitable for quantification of biomarkers at ultralow level.

Free-standing Pt nanowire networks with clean surfaces: Highly sensitive electrochemical detection of nitrite

Support-free interconnected Pt nanowire networks (Pt NWNs) were fabricated by rapidly pouring sodium borohydride (NaBH4) solution into the Pt precursor solution, where hydrogen bubbles were in situ generated from hydrolysis and oxidation of NaBH4 as a dynamic template. There was no any capping agent, surfactant, seed, polymer, or special experimental device involved. The morphology, composition and structure of the samples were mainly characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The architectures displayed highly electrocatalytic behavior toward nitrite oxidation and wide linear ranges of 1.0μM–24.0mM and 24.0–132.0mM, together with high sensitivity (16.94 and 4.34μAmM−1) and low detection limit (0.14μM, S/N=3). It demonstrated the improved electroanalytical performance for nitrite determination because of the unique free-standing Pt nanostructures with clean surfaces.