A systematic structural elucidation of the near-surface active species of the two remarkably active nickel phosphides Ni12P5 and Ni2P on the basis of extensive analytical, microscopic, and spectroscopic investigations is reported. The latter can serve as complementary efficient electrocatalysts in the hydrogen (HER) versus oxygen evolution reaction (OER) in alkaline media. In the OER Ni12P5 shows enhanced performance over Ni2P due to the higher concentration of nickel in this phase, which enables the formation of an amorphous NiOOH/Ni(OH)2 shell on a modified multiphase with a disordered phosphide/phosphite core. The situation is completely reversed in the HER, where Ni2P displayed a significant improvement in electrocatalytic activity over Ni12P5 owing to a larger concentration of phosphide/phosphate species in the shell. Moreover, the efficiently combined use of the two nickel phosphide phases deposited on nickel foam in overall electrocatalytic water splitting is demonstrated by a strikingly low cell v...

Room temperature partial oxidation (corrosion) of cubic CoO led to the formation of mixed valence CoOxwith better electrochemical water oxidation activities in alkaline pH. Activation of both octahedral Co3+and Co2+to layered oxohydroxide–hydroxide during alkaline electrochemical water oxidation has been demonstrated.

The selective oxidation of methane to methanol is a highly challenging target, which is of considerable interest to gain value-added chemicals directly from fuel gas. Copper containing zeolites, such as Cu/mordenite, have been currently reported to be the most efficient catalysts for this reaction. In this work, it is shown that solid-state ion-exchanged Cu/mordenites exhibit a significantly higher activity for the partial oxidation of methane to methanol than comparable reference catalysts, i.e., Cu/mordenites prepared by the conventional liquid-phase ion exchange procedure. The efficiency of these Cu/mordenites remained unchanged over several successive cycles. From temperature-programmed reduction (TPR) measurements, it can be concluded that the solid-state protocol accelerates Cu exchange at the small pores of mordenite: those are positions where the most active Cu species are presumably located. In situ ultraviolet-visible (UV-vis) spectroscopy furthermore indicates that different active clusters including dicopper- and tricopper-oxo complexes are formed in the catalyst upon oxygen treatment. Notably after activation of methane, different methoxy intermediates seem to be generated at the Cu sites from which one is preferably transformed to methanol by reaction with water. It is furthermore described that the applied reaction conditions have considerable influence on the finally observed methanol production from methane.

Self-supported nickel-manganese-based catalysts were synthesized from heterobimetallic nickel manganese oxalate precursors via a versatile reverse micelle approach. The precursors were subjected to thermal degradation (400 °C) in the presence of synthetic air to form respective metal oxides, which were treated under hydrogen (500 °C) to form Ni2 MnO4 -O2 -H2 , Ni6 MnO8 -O2 -H2 and NiO-O2 -H2 . Similarly, the precursors were also treated directly under hydrogen at the same temperature to form Ni2 MnO4 -H2 and Ni6 MnO8 -H2 . The catalysts were extensively investigated by PXRD, SEM, TEM, XPS and BET analyses. The resulting catalysts were applied for dry reforming of methane (DRM) and exhibit better stability and resistance to coking than coprecipitated catalysts. Further, we show that addition of manganese, which is not an active catalyst for DRM alone, to nickel has a significant promotion effect on both the activity and stability of DRM catalysts, and a Ni/Mn ratio lower than 6:1 enables optimized activity for this system.

In the present paper, we demonstrate a versatile approach for the one-pot synthesis of metal oxide yolk@shell nanostructures filled with bimetallic nanocores. This novel approach is based on the principles of hydrophobic nanoreactor soft-templating and is exemplified for the synthesis of various AgAuNP@tin-rich ITO (AgAu@ITOTR) yolk@shell nanomaterials. Hydrophobic nanoreactor soft-templating thereby takes advantage of polystyrene-block-poly(4-vinylpiridine) inverse micelles as two-compartment nanoreactor template, in which the core and the shell of the micelles serve as metal and metal oxide precursor reservoir, respectively. The composition, size and number of AuAg bimetallic nanoparticles incorporated within the ITOTR yolk@shell can easily be tuned. The conductivity of the ITOTR shell and the bimetallic composition of the AuAg nanoparticles, the as-synthesized AuAgNP@ITOTR yolk@shell materials could be used as efficient electrocatalysts for electrochemical glucose oxidation with improved onset potential when compared to their gold counterpart.

Abstractδ‐TaON is prepared by ammonolysis of amorphous Ta2O5 precursor derived via a modified Pechini route (NH3 stream, 760 °C, 1 h; 43% yield).

We present a facile synthesis of bioinspired manganese oxides for chemical and photocatalytic water oxidation, starting from a reliable and versatile manganese(II) oxalate single-source precursor (SSP) accessible through an inverse micellar molecular approach. Strikingly, thermal decomposition of the latter precursor in various environments (air, nitrogen, and vacuum) led to the three different mineral phases of bixbyite (Mn2 O3 ), hausmannite (Mn3 O4 ), and manganosite (MnO). Initial chemical water oxidation experiments using ceric ammonium nitrate (CAN) gave the maximum catalytic activity for Mn2 O3 and MnO whereas Mn3 O4 had a limited activity. The substantial increase in the catalytic activity of MnO in chemical water oxidation was demonstrated by the fact that a phase transformation occurs at the surface from nanocrystalline MnO into an amorphous MnOx (1<x<2) upon treatment with CAN, which acted as an oxidizing agent. Photocatalytic water oxidation in the presence of [Ru(bpy)3 ](2+) (bpy=2,2'-bipyridine) as a sensitizer and peroxodisulfate as an electron acceptor was carried out for all three manganese oxides including the newly formed amorphous MnOx . Both Mn2 O3 and the amorphous MnOx exhibit tremendous enhancement in oxygen evolution during photocatalysis and are much higher in comparison to so far known bioinspired manganese oxides and calcium-manganese oxides. Also, for the first time, a new approach for the representation of activities of water oxidation catalysts has been proposed by determining the amount of accessible manganese centers.

A new phase in the system Sc-Ta-O-N was synthesized by reaction of an amorphous oxide precursor with a gaseous NH3/O2 mixture at 800 °C. Crystal structure determination was performed using X-ray powder data. ScTa2O5N crystallizes in the tetragonal space group P42/mnm (rutile-type structure) and exhibits a brilliant yellow color (optical bandgap: 2.67 eV), making it a promising material for photocatalytical water splitting. Further investigation methods (SEM, TEM, and N2-physisorption) were applied for more detailed characterization of the new phase. Unfortunately, the new compound could not be prepared as pure phase. So far a phase purity of ca. 90 % was the best result.

The synthesis and characterization of functionalized carbon using variable doping profiles are presented. The hybrids were obtained from nitrile-functionalized ionic precursors and a ferric chloride mediator. This way, novel nitrogen doped and nitrogen-sulfur, nitrogen-phosphorus, and nitrogen-boron codoped carbon hybrids with a morphology containing microporous nanometer-sized particles were obtained. As-prepared heteroatom doped carbons exhibited superior electrocatalytic activity toward the oxygen reduction reaction (ORR) in alkaline and acid electrolytes. In particular, both the heteroatom type and iron were found to play crucial roles in improving the catalytic activity of functionalized carbon. It is worth noting that sulfur-nitrogen codoped functionalized materials synthesized in the presence of ferric chloride showed higher activity and stability in comparison to those of the commercial state-of-the-art Pt catalyst in alkaline electrolyte. Moreover, in acid electrolyte, sulfur-nitrogen codoped catalyst rivaled the activity of Pt with a stability outperforming that of Pt. Our X-ray photoelectron spectroscopy (XPS) investigation revealed a distinctive atomic structure in nitrogen-sulfur codoped material in comparison to other codoped catalysts, most likely explaining its superior electrocatalytic activity. This work presents a novel toolbox for designing advanced carbon hybrids with variable heteroatom doping profiles which presents tunable and enhanced ORR performance.

AbstractIn regard to earth‐abundant cobalt water oxidation catalysts, very recent findings show the reorganization of the materials to amorphous active phases under catalytic conditions. To further understand this concept, a unique cobalt‐substituted crystalline zinc oxide (Co:ZnO) precatalyst has been synthesized by low‐temperature solvolysis of molecular heterobimetallic Co4−xZnxO4 (x=1–3) precursors in benzylamine. Its electrophoretic deposition onto fluorinated tin oxide electrodes leads after oxidative conditioning to an amorphous self‐supported water‐oxidation electrocatalyst, which was observed by HR‐TEM on FIB lamellas of the EPD layers. The Co‐rich hydroxide‐oxidic electrocatalyst performs at very low overpotentials (512 mV at pH 7; 330 mV at pH 12), while chronoamperometry shows a stable catalytic current over several hours.

A generalized synthesis of high-quality, mesoporous zeolite (e.g., MFI-type) nanocrystals is presented, based on a biomass-derived, monolithic N-doped carbonaceous template. As an example, ZSM-5 single crystals with desirable large-diameter (12-16 nm) intracrystalline mesopores are synthesized. The platform provides scope to optimize template dimensions and chemistry for the synthesis of a range of micro-/mesoporous crystalline zeolites in a cost-effective and highly flexible manner.

δ-TaON was prepared by reaction of gaseous ammonia with an amorphous tantalum oxide precursor. As a representative of the anatase structure (aristotype) it crystallizes in the tetragonal crystal system with lattice parameters a = 391.954(16) pm and c = 1011.32(5) pm. At temperatures between 800 and 850 °C an irreversible phase transformation to baddeleyite-type β-TaON is observed. While quantum-chemical calculations confirm the metastable character of δ-TaON, its transformation to β-TaON is kinetically controlled. The anion distribution of the anatase-type phase was studied theoretically. In agreement with previous studies, it was found that a configuration with maximal N-N distances is most stable. The calculated band edge energies indicate that δ-TaON is a promising photocatalytic material for redox reactions, e.g., water splitting.

The title compound is prepared by oxidizing ammonolysis of an amorphous Sc‐Ta‐O precursor derived by Pechini‐type sol‐gel processing (800 °, 2 h, NH 3 and O 2 flow rates of 10 and 0.1 l/h, resp., phase purity of 90%).

In nature, photosynthetic water oxidation is efficiently catalysed at a protein-bound μ-oxido Mn4Ca cluster. This cluster consists of earth abundant, non-toxic elements and serves as a paragon for development of synthetic catalysts. In this study we developed porous calcium-manganese oxides with a unique foam-like nanostructure prepared via a facile and robust synthetic route using cyanamide as a porogen. A series of such oxide foams annealed at different temperatures was characterized by TEM, SEM, XRD, N2 physisorption, and X-ray absorption spectroscopy (XAS) in order to correlate crystallinity, atomic structure, surface area and oxidation state of the materials with catalytic activity. Some of the resulting Ca-Mn oxides show high activity as catalysts for water oxidation in the presence of cerium(iv) ammonium nitrate as a non-oxo transfer oxidant. An amorphous calcium-manganese-oxide foam with 130 m(2) g(-1) surface area and Mn oxidation state of +3.6 was identified to be most active; its activity is superior to previously reported Ca-Mn oxides. At the atomic level, this material shares structural motifs with the biological paragon as revealed by dual-edge XAS at the Mn and Ca K-edge. Rather than nanostructure and surface area, the atomic structure of the Ca-Mn oxide and the extent of structural order appear to be crucial determinants of catalytic activity. Fully disordered low-valent Mn materials as well as high-valent but crystalline Mn-Ca oxides are unreactive. Highly disordered variants of layered manganese oxide with Ca and water molecules interfacing layer fragments are most reactive.

In this paper we report immobilization and bioelectrocatalysis of human sulfite oxidase (hSO) on nanostructured antimony doped tin oxide (ATO) thin film electrodes. Two types of ATO thin film electrodes were prepared via evaporation induced self-assembly of ATO nanoparticle sols. The use of a porogen results in different porosity and film thickness. Nevertheless both electrode types reveal similar quasi reversible electrochemical behavior for positive and negatively charged small mediators. Facile and durable immobilization of catalytically active enzyme in a direct electron transfer configuration was achieved without further chemical modification of the ATO surfaces. Interestingly, the binding of hSO onto the ATO surface seems to be not only of electrostatic nature, but also originates from a strong interaction between the histidine-tag of the enzyme and the supporting material. This is suggested from stable sulfite dependent bioelectrocatalytic signals at high ionic strength and imidazole desorption experiments. As such, ATO appears as a promising conductive platform for the immobilization of complex enzymes and their application in bioelectrocatalysis.