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A series of cobaloxime complexes([Co(dmgH)(2)pyCl] (1), [Co(dmgH)(2)(4-COOMe-py)Cl] (2), [Co(dmgH)(2)(4-Me(2)N-py)Cl] (3), [Co(dmgH)(dmgH(2))Cl(2)] (4), [Co(dmgH)(2)(py)(2)](PF(6)) (5), [Co(dmgH)(2)(P(n-Bu)(3))Cl] (6), and [Co(dmgBF(2))(2)(OH(2))(2)] (7), where dmgH = dimethylglyoximate monoanion, dmgH(2) = dimethylglyoxime, dmgBF(2) = (difluoroboryl)dimethylglyoximate anion, and py = pyridinewere synthesized and studied as molecular catalysts for the photogeneration of hydrogen from systems containing a Pt terpyridyl acetylide chromophore and triethanolamine (TEOA) as a sacrificial donor in aqueous acetonitrile. All cobaloxime complexes 1-7 are able to quench the luminescence of the Pt(II) chromophore [Pt(ttpy)(CCPh)]ClO(4) (C1) (ttpy = 4'-p-tolyterpyridine). The most effective electron acceptor for hydrogen evolution is found to be complex 2, which provides the fastest luminescence quenching rate constant for C1 of 1.7 x 10(9) M(-1) s(-1). The rate of hydrogen evolution depends on many factors, including the stability of the catalysts, the driving force for proton reduction, the relative and absolute concentrations of system components (TEOA, Co molecular catalyst, and sensitizer), and the ratio of MeCN/water in the reaction medium. For example, when the concentration of TEOA increases, the rate of H(2) photogeneration is faster and the induction period is shorter. Colloidal cobalt experiments and mercury tests were run to verify that the system is homogeneous and that catalysis does not occur from in situ generated colloidal particles during photolysis. The most effective system examined to date consists of the chromophore C1 (1.1 x 10(-5) M), TEOA (0.27 M), and catalyst complex 1 (2.0 x 10(-4) M) in a MeCN/water mixture (24:1 v/v, total 25 mL); this system has produced approximately 2150 turnovers of H(2) after only 10 h of photolysis with lambda > 410 nm.

Dye-sensitized solar cells (DSSCs) are regarded as prospective solar cells for the next generation of photovoltaic technologies and have become research hotspots in the PV field. The counter electrode, as a crucial component of DSSCs, collects electrons from the external circuit and catalyzes the redox reduction in the electrolyte, which has a significant influence on the photovoltaic performance, long-term stability and cost of the devices. Solar cells, dye-sensitized solar cells, as well as the structure, principle, preparation and characterization of counter electrodes are mentioned in the introduction section. The next six sections discuss the counter electrodes based on transparency and flexibility, metals and alloys, carbon materials, conductive polymers, transition metal compounds, and hybrids, respectively. The special features and performance, advantages and disadvantages, preparation, characterization, mechanisms, important events and development histories of various counter electrodes are presented. In the eighth section, the development of counter electrodes is summarized with an outlook. This article panoramically reviews the counter electrodes in DSSCs, which is of great significance for enhancing the development levels of DSSCs and other photoelectrochemical devices.

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A redox intermedium p-phenylenediamine (PPD) with quick reversible faradaic processes is introduced into KOH electrolyte, referred to as pseudocapacitive effect occurring on the electrode/electrolyte surface. The KOH + PPD electrolyte as potential electrolyte for supercapacitors is investigated by UV-Vis spectroscopy and electrochemical methods. As expected, the supercapacitor with KOH + PPD electrolyte has a much higher electrode specific capacitance (605.225 F g À1 ) than the one with conventional KOH electrolyte (144.037 F g À1 ) at the same current density of 1 A g À1 . Simultaneously, the supercapacitor with KOH + PPD electrolyte exhibits a much higher energy density (19.862 W h kg À1 ) than the supercapacitor with conventional KOH electrolyte (4.458 W h kg À1 ). Furthermore, the supercapacitor with KOH + PPD electrolyte shows superior charge-discharge stability. After 4000 cycles, its capacitive retention ratio is still as high as 94.530%.

Recent advances in metal and metal-free ligand-centred electrocatalytic H2 evolution have been reviewed.

A novel mixed-valent Ag(I)/Ag(0) T(h)-Ag(34) cage was obtained by a one-pot ultrasonic reaction. In the shell of the cage, CO(3)(2-) anion is derived from atmospheric CO(2) and adopts a rare μ(6) bridging mode to link the Ag(I) ions. In the core of the cage, an unprecedented neutral metal cluster with six zero-valent silver atoms is encapsulated.

In this study a series of supramolecular BODIPY-cobaloxime systems Co-Bn (n = 1-4): [{Co(dmgH)2Cl}{4,4-difluoro-8-(4-pyridyl)-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene}] (Co-B1), [{Co(dmgH)2Cl}{4,4-difluoro-8-(4-pyridyl)-1,3,5,7-tetramethyl-2,6-diiodo-4-bora-3a,4a-diaza-s-indacene}] (Co-B2), [{Co(dmgH)2Cl}{4,4-difluoro-8-(3-pyridyl)-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene}] (Co-B3), and [{Co(dmgH)2Cl}{4,4-difluoro-8-(3-pyridyl)-1,3,5,7-tetramethyl-2,6-diiodo-4-bora-3a,4a-diaza-s-indacene}] (Co-B4) (BODIPY = boron dipyrromethene, dmgH = dimethylglyoxime) have been synthesized by replacing one axial chlorine of cobaloxime moieties with the pyridine residues of BODIPYs, and structurally characterized. Absorption spectra show that the optical properties of the BODIPY-cobaloximes are essentially the sum of their constituent components, indicating weak interactions between the cobaloxime units and BODIPY chromophores in the ground state. If any, electronic communications may take place through the intramolecular electron transfer across their orthogonal structures. The possibility of intramolecular electron transfer is further supported by the results of the density functional theory (DFT) calculations at UB3LYP/LANL2DZ levels on Co-B2˙(-) and Co-B4˙(-), which show that the highest occupied molecular orbitals (HOMOs) possess predominantly BODIPY character, while the lowest unoccupied molecular orbitals (LUMOs) are located on the cobalt centers. The HOMO → LUMO transition is an electron-transfer process (BODIPY˙(-) radical anions → cobaloxime fragments). In view of the possible occurrence of electron transfer, these noble-metal-free BODIPY-cobaloximes are studied as single-component homogeneous photocatalysts for H2 generation in aqueous media. Under optimized conditions, the 2,6-diiodo BODIPY-sensitized cobaloxime Co-B4 that contains a meta-pyridyl at the 8-position of BODIPY presents excellent H2 photoproduction catalytic activity with a turnover number (TON) of 85, which is comparable to that of its analogue Co-B2 that has a para-pyridyl attached onto 2,6-diiodo BODIPY (TON = 82); however, both of the noniodinated BODIPY-sensitizer cobaloximes (Co-B1, Co-B3) exhibit a complete lack of activity under the same experimental conditions. These results show that the presence of heavy atoms in the core of BODIPY is essential for the catalytic process and reductive quenching pathways (namely, the intramolecular electron transfers from BODIPY˙(-) species to the cobalt centers) for these photocatalytically active systems of Co-Bn (n = 2 and 4) are thermodynamically feasible for the hydrogen-evolving reaction.