The nanostructured BiVO 4 photoanodes were prepared by electrospinning and were further characterized by XRD, SEM, and XPS, confirming the bulk and surface modification of the electrodes attained by W addition. The role of surface states (SS) during water oxidation for the asprepared photoanodes was investigated by using electrochemical, photoelectrochemical, and impedance spectroscopy measurements. An optimum 2% doping is observed in voltammetric measurements with the highest photocurrent density at 1.23 V RHE under back side illumination. It has been found that a high PEC performance requires an optimum ratio of density of surface states (N SS) with respect to the charge donor density (N d), to give both good conductivity and enough surface reactive sites. The optimum doping (2%) shows the highest N d and SS concentration, which leads to the high film conductivity and reactive sites. The reason for SS acting as reaction sites (i-SS) is suggested to be the reversible redox process of V 5+ /V 4+ in semiconductor bulk to form water oxidation intermediates through the electron trapping process. Otherwise, the irreversible surface reductive reaction of VO 2 + to VO 2+ though the electron trapping process raises the surface recombination. W doping does have an effect on the surface properties of the BiVO 4 electrode. It can tune the electron trapping process to obtain a high concentration of i-SS and less surface recombination. This work gives a further understanding for the enhancement of PEC performance caused by W doping in the field of charge transfer at the semiconductor/electrolyte interface.

Hydrogen peroxide (H2O2) production by electrocatalytic two-electron oxygen reduction shows promise as a replacement for energy-intensive anthraquinone oxidation or H2/O2 direct synthesis. Here, we report on graphene-supported Ni single-atom (SA) electrocatalysts, which are synthesized by a simple surfactant-free reduction process with enhanced electrocatalytic activity and stability. Unlike conventional Ni nanoparticles or alloy catalysts, the well-dispersed Ni-SA sites lack adjacent Ni atoms. This structure promotes H2O2 production by a two-electron oxygen reduction pathway under an alkaline condition (pH = 13). This catalyst exhibited enhanced H2O2 selectivity (>94%) with a considerable mass activity (2.11 A mgNi –1 at 0.60 V vs reversible hydrogen electrode), owing to the presence of oxygen functional groups and isolated Ni sites. Density functional theory calculations provide insights into the role of this catalyst in optimizing the two-electron oxygen reduction reaction pathway with high H2O2 selectivity. This work suggests a new method for controlling reaction pathways in atomically dispersed non-noble catalysts.

The photocatalytic activity for CO(2) reduction and optical and electrochemical properties of two Ru(II)-Re(I) binuclear complexes [Ru(dmb)(2)LRe(CO)(3)Cl](2+) (Ru-Re and Ru=Re, dmb = 4,4'-dimethyl-2,2'-bipyridine) with 1,2-bis(4'-methyl-2,2'-bipyridyl-4-yl)ethane and 1,2-bis(4'-methyl-2,2'-bipyridyl-4-yl)ethene as bridging ligands have been investigated. The conjugation content of the bridging ligands plays an important role in the photocatalytic behavior: a saturated linkage exhibited more efficient than the conjugated.

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A novel tripodal ligand, tris[(4'-methyl-2,2'-bipyridin-4-yl)methyl]carbinol (tb-carbinol) and its homonuclear and heteronuclear Ru(II)-Re(I) complexes have been synthesized and characterized by NMR spectroscopy, elemental analysis, and mass spectroscopy. The spectroscopic, electrochemical and photocatalytic properties of the Ru(II)-Re(I) complexes have been investigated. In these supramolecular complexes with tb-carbinol as a bridging ligand, the intramolecular interaction among the terminal metal centers is very weak. In the cases of Ru(II) and Re(I) heteronuclear systems, when the Re(I) moieties are excited, the emission from the Re(I) moiety is efficiently quenched and the intensity of the emission from the Ru(II) moiety increases. The rate constant of energy transfer from Re(I) moieties to Ru(II) unit in RuRe(2) is 1.7 x 10(8) s(-1). From the point of view of the free energy change, the intramolecular electron transfer from the Ru(II) moiety to the Re(I) moiety could proceed smoothly in the ground state. Both of Ru(2)Re and RuRe(2) show excellent photocatalytic activities to the CO(2) reduction. RuRe(2) exhibits a turnover number of 190 for CO formation compared with 89 from the model complexes system after 16 h of irradiation (TN(CO) calculated based on Ru(II) moiety concentration). Ru(2)Re shows a higher turnover number than the model complexes system, 110 compared with 55 from the model system (TN(CO) calculated based on Re(I) moiety concentration). The bridging ligand of Ru(II)-Re(I) heteronuclear tripodal systems, tb-carbinol, plays an important role in converting radiant energy to chemical energy in the form of CO from CO(2). Enhancement of the photocatalytic response to light in the visible region has been achieved by fabricating supramolecular systems featuring covalently linked Ru(II) and Re(I) moieties.

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A novel tripodal ligand, tris[(4'-methyl-2,2'-bipyridyl-4-yl)methyl]carbinol (L), has been synthesized. The spectroscopic, electrochemical, and photocatalytic properties of the new trinuclear complexes (Ru(2)Re and RuRe(2)) linked by the tripodal bridging ligand L are then investigated. In addition, 2-fold-improved photocatalytic activities were obtained in the case of these trinuclear complexes compared to the mixtures of the appropriate monometallic model complexes in the reduction of CO(2) under visible irradiation.

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