The efficient generation of dihydrogen on molecularly modified p-Si(111) has remained a challenge due to the low barrier heights observed on such surfaces. The band-edge and barrier height challenge is a primary obstruction to progress in the area of integration of molecular H2 electrocatalysts with silicon photoelectrodes. In this work, we demonstrate that an optimal combination of organic passivating agent and inorganic metal oxide leads to H2 evolution at photovoltages positive of RHE. Modulation of the passivating R group [CH3 → Ph → Naph → Anth → Ph(OMe)2] improves both the band-edge position and ΔV (Vonset - VJmax). Subsequent atomic layer deposition (ALD) of Al2O3 or TiO2 along with ALD-Pt deposition results in to our knowledge the first example of a positive H2 operating potential on molecularly modified Si(111). Mott-Schottky analyses reveal that the flat-band potential of the stable Ph(OMe)2 surface approaches that of the native (but unstable) hydride-terminated surface. The series resistance is diminished by the methoxy functional groups on the phenyl unit, due to its chemical and electronic connectivity with the TiO2 layer. Overall, judicious choice of the R group in conjunction with TiO2|Pt effects H2 generation on p-Si(111) photoelectrodes (Voc = 207 ± 5.2 mV; Jsc = -21.7 mA/cm(2); ff = 0.22; ηH2 = 0.99%). These results provide a viable hybrid strategy toward the operation of catalysts on molecularly modified p-Si(111).

We demonstrate the covalent attachment and catalytic function of a nickel-phosphine H2 evolution catalyst to a p-Si(111) photoelectrode. The covalently assembled semiconductor|molecular construct achieves a synergistic improvement (ΔVonset = +200 mV) as compared to a solution of [(PNP)2Ni](2+) in contact with a p-Si(111)-CH3 photoelectrode.

Mono-iron hydrogenase was the third type of hydrogenase discovered. Its Lewis acidic iron(II) centre promotes the heterolytic cleavage of the H-H bond and this non-redox H activation distinguishes it from the well-studied dinuclear [FeFe] and [NiFe] hydrogenases. Cleavage of the H-H bond is followed by hydride transfer to the enzyme's organic substrate, HMPT, which serves as a CO 'carrier' in methanogenic pathways. Here we report a scaffold-based synthetic approach by which to model mono-iron hydrogenase using an anthracene framework, which supports a biomimetic fac-C,N,S coordination motif to an iron(II) centre. This arrangement includes the biomimetic and organometallic Fe-C σ bond, which enables bidirectional activity reminiscent of the native enzyme: the complex activates H under mild conditions, and catalyses C-H hydride abstraction plus H generation from a model substrate. Notably, neither H activation nor C-H hydride abstraction was observed in the analogous complex with a pincer-type mer-C,N,S ligation, emphasizing the importance of the fac-C,N,S-iron(II) motif in promoting enzyme-like reactivity.

We report the fabrication of a {semiconductor}|{metal oxide}|{molecular catalyst} construct for the photogeneration of dihydrogen (H2) under illumination, including band-edge modulation of the semiconductor electrode depending on the identity of Si(111)-R and the metal oxide. Briefly, a synergistic band-edge modulation is observed upon (i) the introduction of a p-Si|n-AZO heterojunction and (ii) introduction of an organic dimethoxyphenyl (diMeOPh) group at the heterojunction interface; the AZO also serves as a transparent and conductive conduit, which was capped with an ultrathin layer (20 Å) of amorphous TiO2 for stability. A phosphonate-appended PNP ligand and its Ni complex were then adsorbed to the p/n heterojunction for photoelectrochemical H2 generation (figures of merit: Vonset ≈ + 0.03 V vs NHE, Jmax ≈ 8 mA cm(-2) at 60 mM TsOH).

An in situ generated cationic allylpalladium complex bearing N‐heterocyclic carbene (NHC) ligands, derived from the reaction of [(η3‐C3H5)Pd(NHC)Cl] with AgX (X = BF4 or SbF6), is an active catalyst for the addition polymerization of norbornene and norbornene derivatives [5‐norbornene‐2‐carboxylic acid methyl ester (b) and 5‐norbornene‐2‐carboxylic acid n‐butyl ester (c)] with an ester group containing a large portion of endo‐isomers. The catalytic activities, polymer yields, molecular weights, and molecular weight distributions of polynorbornenes were investigated under various reaction conditions: the catalytic activity was highly dependent on the counteranion, the reaction solvent, and the reaction temperature. For b, as the portion of an endo‐isomer increased, the activity of 13(SbF −6) was much higher than those of 14 and 15, and for c (exo/endo = 95:5), the maximum turn over number (TON) was observed with 15(SbF −6). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3042–3052, 2007

Platinum N-heterocyclic carbene (NHC) complexes have been synthesized and used as precatalysts in the reductive cyclization of diynes and eynes. 2,5-Dihydrofurans, -pyrroles, and -cyclopentenes were obtained as reductive cyclization products from oxygen-, nitrogen-, and carbon-tethered substrates, respectively. The yield and product of the reaction were highly dependent upon the substrate and the substituent on the alkyne.

A mononuclear W(iv) bis-dithiolene complex reduces CO2 to formate while generating a dinuclear W(v) complex.

Bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are necessary in the renewable energy systems. However, the kinetically slow and large energy-demanding procedures of oxygen electrocatalysis make the preparation of bifunctional catalysts difficult. In this work, we report a novel hierarchical GdFeO 3 perovskite oxide of a spherelike nanostructure and surface modification with the group X heterometal oxides. The nanostructured GdFeO 3 layer behaved as a bifunctional electrocatalyst in the oxygen electrocatalysis of OER and ORR. Moreover, the surface decoration with catalytically active PtO x + Ni/NiO nanoparticles enhanced the electrocatalytic performances substantially. Incorporation of mesoporous PtO x + Ni/NiO nanoparticles into the porous GdFeO 3 nanostructure enlarged the electrochemically active surface area and provided the interconnected nanostructures to facilitate the OER/ORR. The nanostructures were visualized by scanning electron microscopy and transmission electron microscopy images, and the surface area and pore size of nanoparticles were analyzed from N 2 adsorption/desorption isotherms. Tafel analysis indicates that surface modification effectively improves the kinetics of oxygen reactions and accordingly increases the electrocatalytic efficiency. Finally, the 2 wt % PtO x + NiO|GdFeO 3 (x = 0, 1, and 2) electrode achieved the enhanced OER performance with an overpotential of 0.19 V at 10 mA/cm 2 in an alkaline solution and a high turnover frequency of 0.28 s −1 at η = 0.5 V. Furthermore, the ORR activity is observed with an onset potential of 0.80 V and a half-wave potential (E 1/2 ) of 0.40 V versus reversible hydrogen electrode.