Highly Ordered Periodic Au/TiO₂ Hetero-Nanostructures for Plasmon-Induced Enhancement of the Activity and Stability for Ethanol Electro-oxidation

The catalytic electro-oxidation of ethanol is the essential technique for direct alcohol fuel cells (DAFCs) in the area of alternative energy for the ability of converting the chemical energy of alcohol into the electric energy directly. Developing highly efficient and stable electrode materials with antipoisoning ability for ethanol electro-oxidation remains a challenge. A highly ordered periodic Au-nanoparticle (NP)-decorated bilayer TiO₂ nanotube (BTNT) heteronanostructure was fabricated by a two-step anodic oxidation of Ti foil and the subsequent photoreduction of HAuCl₄. The plasmon-induced charge separation on the heterointerface of Au/TiO₂ electrode enhances the electrocatalytic activity and stability for the ethanol oxidation under visible light irradiation. The highly ordered periodic heterostructure on the electrode surface enhanced the light harvesting and led to the greater performance of ethanol electro-oxidation under irradiation compared with the ordinary Au NPs-decorated monolayer TiO₂ nanotube (MTNT). This novel Au/TiO₂ electrode also performed a self-cleaning property under visible light attributed to the enhanced electro-oxidation of the adsorbed intermediates. This light-driven enhancement of the electrochemical performances provides a development strategy for the design and construction of DAFCs

One-Step Synthesis of a Self-Supported Copper Phosphide Nanobush for Overall Water Splitting

Developing cheap, stable, and efficient electrocatalysts is of extreme importance in the effort to replace noble metal electrocatalysts for use in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). We report a three-dimensional self-supported Cu₃P nanobush (NB) catalyst directly grown on a copper mesh via a one-step method. This nanostructure exhibits a superior catalytic activity of achieving a current density of 10 mA cm^–2 at 120 mV and exhibits a long-term stability in acid solutions. It shows a Tafel slope of 72 mV dec^–1 and an onset potential of −44 mV. This catalyst displays a good catalytic activity in basic electrolytes, reaching a current density of 10 mA cm^–2 at the overpotential values of 252 and 380 mV for HER and OER, respectively. The bifunctional Cu₃P NB/Cu catalyst exhibits better catalytic performances than the Pt/C and IrO₂ catalysts in a two-electrode electrolyzer for overall water splitting

Characterization of Barley Serpin Z7 That Plays Multiple Roles in Malt and Beer

Barley protein Z7 (BSZ7) is a well-known serine protease inhibitor that was regarded as a major effector of beer foam stability. Moreover, it has also been suggested to participate in haze formation and affect wort filterability. The present study purified BSZ7 from barley malt and characterized its secondary structure and modification, as well as its relationship with peroxidase, to elucidate the molecular base of BSZ7 that supports its multiple roles in malt and beer. It was found that after 30 min of heating, the secondary structure was not affected. BSZ7 has no inhibiting effect on nonspecific protease originated from malt, suggesting its negative role in wort filterability was accomplished by other means. Furthermore, the glycation of BSZ7 by the Maillard reaction may make some contribution to its survival during wort boiling. The interaction of BSZ7 with polysaccharides and polyphenols found by adding experiment may explain how it acts as a negative factor on wort filterability. Greater understanding of BSZ7 and other proteins of malts will lead to better improvements in brewing quality

Micro Galvanic Cell To Generate PtO and Extend the Triple-Phase Boundary during Self-Assembly of Pt/C and Nafion for Catalyst Layers of PEMFC

The self-assembly powder (SAP) with varying Nafion content was synthesized and characterized by XRD, XPS, HRTEM, and mapping. It is observed that the oxygen from oxygen functional groups transfers to the surface of Pt and generate PtO during the process of self-assembly with the mechanism of micro galvanic cell, where Pt, carbon black, and Nafion act as the anode, cathode and electrolyte, respectively. The appearance of PtO on the surface of Pt leads to a turnover of Nafion structure, and therefore more hydrophilic sulfonic groups directly contact with Pt, and thus the triple-phase boundary (TPB) has been expanded

Metal–Organic Framework-Induced Synthesis of Ultrasmall Encased NiFe Nanoparticles Coupling with Graphene as an Efficient Oxygen Electrode for a Rechargeable Zn–Air Battery

Rational design of electrocatalysts to replace the noble-metal-based materials for oxygen reactions is highly desirable but challenging for rechargeable metal–air batteries. Herein, we demonstrate a unique two stage encapsulation strategy to regulate the structure and performance of catalysts featured with thin graphene nanosheets coupling with full encapsulated ultrafine and high-loaded (∼25 wt %) transition metal nanoparticles (TMs@NC_X) for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). By optimizing the electronic modulation effect from suitable metal cores, the best NiFe@NC_X catalyst exhibits high stability and activity with an onset potential of 1.03 V for ORR and an overpotential of only 0.23 V at 10 mA cm^–2 for OER, which is superior to commercial Pt/C and IrO₂ catalysts. Rechargeable Zn–air battery using NiFe@NC_X catalyst exhibited an unprecedented small charge–discharge overpotential of 0.78 V at 50 mA cm^–2, high reversibility, and stability, holding great promise for the practical implementation of rechargeable metal–air batteries

Nanoporous Sulfur-Doped Copper Oxide (Cu₂O_<i>x</i>S_1–<i>x</i>) for Overall Water Splitting

Developing active and bifunctional noble metal-free electrocatalysts is crucial for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in the full water splitting process. A ternary nanoporous sulfur-doped copper oxide (Cu₂O_<i>x</i>S_1–<i>x</i>) was successfully synthesized on Cu foam. The obtained Cu₂O_<i>x</i>S_1–<i>x</i>/Cu shows robust electrocatalytic activity toward HER with a low overpotential of 40 mV at 10 mA cm^–2 and a Tafel slope of 68 mV dec^–1 and exhibits long-term stability in acid solution. Moreover, Cu₂O_<i>x</i>S_1–<i>x</i> shows excellent electrocatalytic activity for OER, HER, and overall water splitting as a bifunctional catalyst in 1.0 M KOH electrolyte. The sulfur doping strategy implemented here can greatly improve the catalytic performance and stability in both acidic and alkaline water electrolyzers and presents an efficient catalyst for overall water splitting

Transformation from Silver Nanoprisms to Nanodecahedra in a Temperature-Controlled Photomediated Synthesis

The photomediated transformation of silver nanoparticles is both synthetically useful and mechanistically intriguing. Temperature effects on photochemical synthesis of silver nanoparticles are investigated. The morphology of final products is strongly dependent on the reaction temperature: nanodecahedra are formed at a low temperature of 20 °C; nanoprisms are formed at a higher temperature of 40 °C; and a mixture of shapes results at 30 °C. An interesting transformation process is observed at a lower temperature of 20 °C: silver nanoprisms are grown first and then transformed into nanodecahedra completely. We propose that silver seeds in a type of multitwinning are more stable than the platelike structure at lower temperature during the photochemical growth process. The transformed silver nanodecahedra exhibit greatly superior enhancement of Raman scattering compared to silver nanoprisms. These findings may provide a new insight on photomediated synthesis of silver nanostructures and suggest a new way of thinking about control over the morphology of nanoparticles

<i>In Situ</i> X‑ray Diffraction Study of Co–Al Nanocomposites as Catalysts for Ammonia Decomposition

Co–Al nanocomposite materials as active and stable catalysts for ammonia decomposition have been synthesized by a one-pot evaporation-induced self-assembly method. The catalysts were characterized by various techniques including powder X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), X-ray photoelectron spectroscopy (XPS), N₂ adsorption/desorption, and transmission/scanning electron microscopy (TEM/SEM). Especially, <i>in situ</i> XRD under catalytic reaction conditions was performed, and metallic Co with a cubic structure was identified to be most probably the active crystalline phase for the decomposition of ammonia; also, contribution of CoO to the catalytic activity cannot be excluded. Most importantly, the introduction of alumina can significantly suppress the agglomeration of the active metallic Co phase and thus maintain the high activity of the cobalt catalyst

Highly Dispersed Copper Oxide Clusters as Active Species in Copper-Ceria Catalyst for Preferential Oxidation of Carbon Monoxide

Copper-ceria is one of the very active catalysts for the preferential oxidation of carbon monoxide (CO-PROX) reaction, which is also a typical system in which the complexity of copper chemistry is clearly exhibited. In the present manuscript, copper–ceria catalysts with different Cu contents up to 20 wt % supported on CeO₂ nanorods were synthesized by a deposition–precipitation (DP) method. The as-prepared samples were characterized by various structural and textural detections including X-ray diffraction (XRD), Vis-Raman, transmission electron microscopy (TEM), <i>ex situ</i>/<i>in situ</i> X-ray absorption fine structure (XAFS), and temperature-programmed reduction by hydrogen (H₂-TPR). It has been confirmed that the highly dispersed copper oxide (CuO_<i>x</i>) clusters, as well as the strong interaction of Cu-[O_<i>x</i>]-Ce structure, were the main copper species deposited onto the ceria surface. No separated copper phase was detected for both preoxidized and prereduced samples with the Cu contents up to 10 wt %. The fresh copper–ceria catalysts were pretreated in either O₂- or H₂-atmosphere and then tested for the CO-PROX reaction at a space velocity (SV) of 60 000 mL·h^–1·g_cat^–1. The prereduced 5 and 10 wt % Cu samples exhibited excellent catalytic performance with high CO conversions (>50%, up to 100%) and O₂ selectivities (>60%, up to 100%) within a wide temperature window of 80–140 °C. The <i>in situ</i> XAFS technique was carried out to monitor the structural evolution on the copper–ceria catalysts during the PROX experiments. The X-ray absorption near edge spectra (XANES) profiles, by the aid of linear combination analysis, identified the oxidized Cu­(II) were the dominant copper species in both O₂- and H₂-pretreated samples after CO-PROX at 80 °C. Furthermore, the extended X-ray absorption fine structure (EXAFS) fitting results, together with the corresponding H₂-TPR data distinctly determined that the highly dispersed CuO_<i>x</i> (<i>x</i> = 0.2−0.5) cluster, other than the Cu–[O_<i>x</i>]–Ce (<i>x</i> = 0.7−3.2) structure, were the crucial active species for the studied CO-PROX reaction

Microporous Framework Induced Synthesis of Single-Atom Dispersed Fe-N‑C Acidic ORR Catalyst and Its in Situ Reduced Fe‑N₄ Active Site Identification Revealed by X‑ray Absorption Spectroscopy

Developing highly efficient, low-cost oxygen reduction catalysts, especially in acidic medium, is of significance toward fuel cell commercialization. Although pyrolyzed Fe-N-C catalysts have been regarded as alternatives to platinum-based catalytic materials, further improvement requires precise control of the Fe-N_<i>x</i> structure at the molecular level and a comprehensive understanding of catalytic site structure and the ORR mechanism on these materials. In this report, we present a microporous metal–organic-framework-confined strategy toward the preferable formation of single-atom dispersed catalysts. The onset potential for Fe-N-C is 0.92 V, comparable to that of Pt/C and outperforming most noble-metal-free catalysts ever reported. A high-spin Fe³⁺-N₄ configuration is revealed by the ⁵⁷Fe Mössbauer spectrum and X-ray absorption spectroscopy for Fe L-edge, which will convert to Fe²⁺-N₄ at low potential. The in situ reduced Fe²⁺-N₄ moiety from high-spin O_<i>x</i>-Fe³⁺-N₄ contributes to most of the ORR activity due to its high turnover frequency (TOF) of ca. 1.71 e s^–1 sites^–1