Solar-Driven Microbial Photoelectrochemical Cells with a Nanowire Photocathode

We report a self-biased, solar-driven microbial photoelectrochemical cell (solar MPC) that can produce sustainable energy through coupling the microbial catalysis of biodegradable organic matter with solar energy conversion. The solar MPC consists of a p-type cuprous oxide nanowire-arrayed photocathode and an electricigen (Shewanella oneidensis MR-1)-colonizing anode, which can harvest solar energy and bioenergy, respectively. The photocathode and bioanode are interfaced by matching the redox potentials of bacterial cells and the electronic bands of semiconductor nanowires. We successfully demonstrated substantial current generation of 200 μA from the MPC device based on the synergistic effect of the bioanode (projected area of 20 cm2) and photocathode (projected area of 4 cm2) at zero bias under white light illumination of 20 mW/cm2. We identified the transition of rate-limiting step from the photocathode to the bioanode with increasing light intensities. The solar MPC showed self-sustained operation for more than 50 h in batch-fed mode under continuous light illumination. The ability to tune the synergistic effect between microbial cells and semiconductor nanowire systems could open up new opportunities for microbial/nanoelectronic hybrid devices with unique applications in energy conversion, environmental protection, and biomedical research

The First Example of Tetraosmium Carbonyl Clusters Containing (μ₃-NH) Nitrene Ligands: Syntheses and Crystal Structures

The reaction of [Os4(μ-H)4(CO)12] with o-tert-butylhydroxylamine hydrochloride (tBuONH2·HCl) in the presence of trimethylamine-N-oxide (Me3NO) in dichloromethane afforded [Os4(μ-H)4(CO)11{η1-NH2OtBu}] (1) in high yield. Upon the addition of tetrafluoroboric acid (HBF4) into the solution of 1 in acetonitrile, the novel cationic cluster [Os4(μ-H)4(CO)11(μ-NH2)(NCMe)][BF4] (2) formed. Reaction of 1 with HBF4 in the presence of diphenylacetylene gave two geometric isomers, [Os4(μ-H)2(CO)11(μ-NH2){μ-η3-Ph(CHC)Ph}] (3) and [Os4(μ-H)2(CO)11(μ-NH2)(η1-Ph(CHC)Ph)] (4). Treatment of 2 with excess Me3NO in acetonitrile gave [Os4(μ-H)4(CO)10(μ-NH2)(NCMe)2][BF4] (5). The carbonylation of 2 in the refluxing chloroform afforded the neutral clusters [Os3(μ-H)2(CO)9(μ-NH2)Cl] (6) and [Os4(μ-H)3(CO)12(μ-NH2)] (7). Protonation of 7 with trifluoromethylsulfonic acid, CF3SO3H, gave another cationic cluster, [Os4(μ-H)4(CO)12(μ-NH2)][CF3SO3] (8), which is an analogue of 2. Refluxing of 7 in toluene under an argon atmosphere afforded [Os4(μ-H)2(CO)12(μ3-NH)] (9), which is the first example of (μ3-NH) nitrene ligands containing tetraosmium carbonyl clusters. The solid-state structures of 2−9 were established by X-ray analysis. The 1H NMR properties of these clusters were studied, and a correlation between the chemical shift and the structural geometry was established

The First Example of Tetraosmium Carbonyl Clusters Containing (μ₃-NH) Nitrene Ligands: Syntheses and Crystal Structures

The reaction of [Os4(μ-H)4(CO)12] with o-tert-butylhydroxylamine hydrochloride (tBuONH2·HCl) in the presence of trimethylamine-N-oxide (Me3NO) in dichloromethane afforded [Os4(μ-H)4(CO)11{η1-NH2OtBu}] (1) in high yield. Upon the addition of tetrafluoroboric acid (HBF4) into the solution of 1 in acetonitrile, the novel cationic cluster [Os4(μ-H)4(CO)11(μ-NH2)(NCMe)][BF4] (2) formed. Reaction of 1 with HBF4 in the presence of diphenylacetylene gave two geometric isomers, [Os4(μ-H)2(CO)11(μ-NH2){μ-η3-Ph(CHC)Ph}] (3) and [Os4(μ-H)2(CO)11(μ-NH2)(η1-Ph(CHC)Ph)] (4). Treatment of 2 with excess Me3NO in acetonitrile gave [Os4(μ-H)4(CO)10(μ-NH2)(NCMe)2][BF4] (5). The carbonylation of 2 in the refluxing chloroform afforded the neutral clusters [Os3(μ-H)2(CO)9(μ-NH2)Cl] (6) and [Os4(μ-H)3(CO)12(μ-NH2)] (7). Protonation of 7 with trifluoromethylsulfonic acid, CF3SO3H, gave another cationic cluster, [Os4(μ-H)4(CO)12(μ-NH2)][CF3SO3] (8), which is an analogue of 2. Refluxing of 7 in toluene under an argon atmosphere afforded [Os4(μ-H)2(CO)12(μ3-NH)] (9), which is the first example of (μ3-NH) nitrene ligands containing tetraosmium carbonyl clusters. The solid-state structures of 2−9 were established by X-ray analysis. The 1H NMR properties of these clusters were studied, and a correlation between the chemical shift and the structural geometry was established

The First Example of Tetraosmium Carbonyl Clusters Containing (μ₃-NH) Nitrene Ligands: Syntheses and Crystal Structures

The reaction of [Os4(μ-H)4(CO)12] with o-tert-butylhydroxylamine hydrochloride (tBuONH2·HCl) in the presence of trimethylamine-N-oxide (Me3NO) in dichloromethane afforded [Os4(μ-H)4(CO)11{η1-NH2OtBu}] (1) in high yield. Upon the addition of tetrafluoroboric acid (HBF4) into the solution of 1 in acetonitrile, the novel cationic cluster [Os4(μ-H)4(CO)11(μ-NH2)(NCMe)][BF4] (2) formed. Reaction of 1 with HBF4 in the presence of diphenylacetylene gave two geometric isomers, [Os4(μ-H)2(CO)11(μ-NH2){μ-η3-Ph(CHC)Ph}] (3) and [Os4(μ-H)2(CO)11(μ-NH2)(η1-Ph(CHC)Ph)] (4). Treatment of 2 with excess Me3NO in acetonitrile gave [Os4(μ-H)4(CO)10(μ-NH2)(NCMe)2][BF4] (5). The carbonylation of 2 in the refluxing chloroform afforded the neutral clusters [Os3(μ-H)2(CO)9(μ-NH2)Cl] (6) and [Os4(μ-H)3(CO)12(μ-NH2)] (7). Protonation of 7 with trifluoromethylsulfonic acid, CF3SO3H, gave another cationic cluster, [Os4(μ-H)4(CO)12(μ-NH2)][CF3SO3] (8), which is an analogue of 2. Refluxing of 7 in toluene under an argon atmosphere afforded [Os4(μ-H)2(CO)12(μ3-NH)] (9), which is the first example of (μ3-NH) nitrene ligands containing tetraosmium carbonyl clusters. The solid-state structures of 2−9 were established by X-ray analysis. The 1H NMR properties of these clusters were studied, and a correlation between the chemical shift and the structural geometry was established

The First Example of Tetraosmium Carbonyl Clusters Containing (μ₃-NH) Nitrene Ligands: Syntheses and Crystal Structures

The reaction of [Os4(μ-H)4(CO)12] with o-tert-butylhydroxylamine hydrochloride (tBuONH2·HCl) in the presence of trimethylamine-N-oxide (Me3NO) in dichloromethane afforded [Os4(μ-H)4(CO)11{η1-NH2OtBu}] (1) in high yield. Upon the addition of tetrafluoroboric acid (HBF4) into the solution of 1 in acetonitrile, the novel cationic cluster [Os4(μ-H)4(CO)11(μ-NH2)(NCMe)][BF4] (2) formed. Reaction of 1 with HBF4 in the presence of diphenylacetylene gave two geometric isomers, [Os4(μ-H)2(CO)11(μ-NH2){μ-η3-Ph(CHC)Ph}] (3) and [Os4(μ-H)2(CO)11(μ-NH2)(η1-Ph(CHC)Ph)] (4). Treatment of 2 with excess Me3NO in acetonitrile gave [Os4(μ-H)4(CO)10(μ-NH2)(NCMe)2][BF4] (5). The carbonylation of 2 in the refluxing chloroform afforded the neutral clusters [Os3(μ-H)2(CO)9(μ-NH2)Cl] (6) and [Os4(μ-H)3(CO)12(μ-NH2)] (7). Protonation of 7 with trifluoromethylsulfonic acid, CF3SO3H, gave another cationic cluster, [Os4(μ-H)4(CO)12(μ-NH2)][CF3SO3] (8), which is an analogue of 2. Refluxing of 7 in toluene under an argon atmosphere afforded [Os4(μ-H)2(CO)12(μ3-NH)] (9), which is the first example of (μ3-NH) nitrene ligands containing tetraosmium carbonyl clusters. The solid-state structures of 2−9 were established by X-ray analysis. The 1H NMR properties of these clusters were studied, and a correlation between the chemical shift and the structural geometry was established

The First Example of Tetraosmium Carbonyl Clusters Containing (μ₃-NH) Nitrene Ligands: Syntheses and Crystal Structures

The reaction of [Os4(μ-H)4(CO)12] with o-tert-butylhydroxylamine hydrochloride (tBuONH2·HCl) in the presence of trimethylamine-N-oxide (Me3NO) in dichloromethane afforded [Os4(μ-H)4(CO)11{η1-NH2OtBu}] (1) in high yield. Upon the addition of tetrafluoroboric acid (HBF4) into the solution of 1 in acetonitrile, the novel cationic cluster [Os4(μ-H)4(CO)11(μ-NH2)(NCMe)][BF4] (2) formed. Reaction of 1 with HBF4 in the presence of diphenylacetylene gave two geometric isomers, [Os4(μ-H)2(CO)11(μ-NH2){μ-η3-Ph(CHC)Ph}] (3) and [Os4(μ-H)2(CO)11(μ-NH2)(η1-Ph(CHC)Ph)] (4). Treatment of 2 with excess Me3NO in acetonitrile gave [Os4(μ-H)4(CO)10(μ-NH2)(NCMe)2][BF4] (5). The carbonylation of 2 in the refluxing chloroform afforded the neutral clusters [Os3(μ-H)2(CO)9(μ-NH2)Cl] (6) and [Os4(μ-H)3(CO)12(μ-NH2)] (7). Protonation of 7 with trifluoromethylsulfonic acid, CF3SO3H, gave another cationic cluster, [Os4(μ-H)4(CO)12(μ-NH2)][CF3SO3] (8), which is an analogue of 2. Refluxing of 7 in toluene under an argon atmosphere afforded [Os4(μ-H)2(CO)12(μ3-NH)] (9), which is the first example of (μ3-NH) nitrene ligands containing tetraosmium carbonyl clusters. The solid-state structures of 2−9 were established by X-ray analysis. The 1H NMR properties of these clusters were studied, and a correlation between the chemical shift and the structural geometry was established

The First Example of Tetraosmium Carbonyl Clusters Containing (μ₃-NH) Nitrene Ligands: Syntheses and Crystal Structures

The reaction of [Os4(μ-H)4(CO)12] with o-tert-butylhydroxylamine hydrochloride (tBuONH2·HCl) in the presence of trimethylamine-N-oxide (Me3NO) in dichloromethane afforded [Os4(μ-H)4(CO)11{η1-NH2OtBu}] (1) in high yield. Upon the addition of tetrafluoroboric acid (HBF4) into the solution of 1 in acetonitrile, the novel cationic cluster [Os4(μ-H)4(CO)11(μ-NH2)(NCMe)][BF4] (2) formed. Reaction of 1 with HBF4 in the presence of diphenylacetylene gave two geometric isomers, [Os4(μ-H)2(CO)11(μ-NH2){μ-η3-Ph(CHC)Ph}] (3) and [Os4(μ-H)2(CO)11(μ-NH2)(η1-Ph(CHC)Ph)] (4). Treatment of 2 with excess Me3NO in acetonitrile gave [Os4(μ-H)4(CO)10(μ-NH2)(NCMe)2][BF4] (5). The carbonylation of 2 in the refluxing chloroform afforded the neutral clusters [Os3(μ-H)2(CO)9(μ-NH2)Cl] (6) and [Os4(μ-H)3(CO)12(μ-NH2)] (7). Protonation of 7 with trifluoromethylsulfonic acid, CF3SO3H, gave another cationic cluster, [Os4(μ-H)4(CO)12(μ-NH2)][CF3SO3] (8), which is an analogue of 2. Refluxing of 7 in toluene under an argon atmosphere afforded [Os4(μ-H)2(CO)12(μ3-NH)] (9), which is the first example of (μ3-NH) nitrene ligands containing tetraosmium carbonyl clusters. The solid-state structures of 2−9 were established by X-ray analysis. The 1H NMR properties of these clusters were studied, and a correlation between the chemical shift and the structural geometry was established

Insights into the pH-dependent Behavior of N‑Doped Carbons for the Oxygen Reduction Reaction by First-Principles Calculations

The oxygen reduction reaction (ORR) is one of the important cathodic reactions because of its central role in important applications, such as fuel cells. Nitrogen (N)-doped carbons have been demonstrated to be one of the most promising and affordable materials as an ORR catalyst. However, their catalytic performance under acidic conditions is about two orders inferior than that under basic conditions, which is too low to be significant. Such an unexpected pH-dependent behavior has not been adequately explained and is still under debate. In this work, we investigate this pH-dependent behavior by using first-principles density functional theory (DFT) calculations. With consideration of the solvation effect and applied voltage, our simulation results show switching of active sites from pyridinic N to graphitic N that explains the changes in reaction rates from acidic to alkaline conditions. These observations not only well explain the existing experiment but also provide guidance for designing more efficient carbon-based catalysts for the ORR in an acidic medium

Synergistic Effect of CdSe Quantum Dot Sensitization and Nitrogen Doping of TiO₂ Nanostructures for Photoelectrochemical Solar Hydrogen Generation

We report the synthesis and photoelectrochemical (PEC) studies of TiO2 nanoparticles and nanowires simultaneously doped with nitrogen and sensitized with CdSe quantum dots (QDs). These novel nanocomposite structures have been applied successfully as photoanodes for PEC hydrogen generation using Na2S and Na2SO3 as sacrificial reagents. We observe significant enhanced photoresponse in these nanocomposites compared to N-doped TiO2 or CdSe QD sensitized TiO2. The enhancement is attributed to the synergistic effect of CdSe sensitization and N-doping that facilitate hole transfer/transport from CdSe to TiO2 through oxygen vacancy states (Vo) mediated by N-doping. The results demonstrate the importance of designing and manipulating the energy band alignment in composite nanomaterials for fundamentally improving charge separation and transport and thereby PEC properties

Double-Sided CdS and CdSe Quantum Dot Co-Sensitized ZnO Nanowire Arrays for Photoelectrochemical Hydrogen Generation

We report the design and characterization of a novel double-sided CdS and CdSe quantum dot cosensitized ZnO nanowire arrayed photoanode for photoelectrochemical (PEC) hydrogen generation. The double-sided design represents a simple analogue of tandem cell structure, in which the dense ZnO nanowire arrays were grown on an indium−tin oxide substrate followed by respective sensitization of CdS and CdSe quantum dots on each side. As-fabricated photoanode exhibited strong absorption in nearly the entire visible spectrum up to 650 nm, with a high incident-photon-to-current-conversion efficiency (IPCE) of ∼45% at 0 V vs Ag/AgCl. On the basis on a single white light illumination of 100 mW/cm2, the photoanode yielded a significant photocurrent density of ∼12 mA/cm2 at 0.4 V vs Ag/AgCl. The photocurrent and IPCE were enhanced compared to single quantum dot sensitized structures as a result of the band alignment of CdS and CdSe in electrolyte. Moreover, in comparison to single-sided cosensitized layered structures, this double-sided architecture that enables direct interaction between quantum dot and nanowire showed improved charge collection efficiency. Our result represents the first double-sided nanowire photoanode that integrates uniquely two semiconductor quantum dots of distinct band gaps for PEC hydrogen generation and can be possibly applied to other applications such as nanostructured tandem photovoltaic cells