The photoinduced hydrogen evolution reaction (HER) by decamethylruthenocene,C p 2 *Ru II (Cp* = C 5 Me 5 ), is reported. The use of am etallocene to photoproduce hydrogen is presented as an alternative strategy to reduce protons without involving an additional photosensitizer.T he mechanism was investigated by (spectro)electrochemical and spectroscopic (UV/Vis and 1 HNMR) measurements.T he photoactivated hydride involved was characterized spectroscopically and the resulting [Cp 2 *Ru III ] + species was electrochemically regenerated in situ on af luorinated tin oxide electrode surface.Apromising internal quantum yield of 25 %w as obtained. Optimal experimental conditionsespecially the use of weakly coordinating solvent and counterions-are discussed.Thedevelopmentofsimpleandefficientmethodstoproduce molecular hydrogen (H 2 )i st he focus of intense research. Va rious state-of-the-art multicomponent artificial photosystems for H 2 generation are currently under heavy scrutiny and generally consist of ah ighly engineered catalyst, photosensitizer,electron mediator or relay combinations, [1] and are often fueled by sacrificial electron donors (for example, triethylamine, [2] triethanolamine, [2b] benzyl-dihydronicotinamide, [3] and so forth). Thel atter irreversibly oxidizes upon charge transfer and provides protons and electrons to the catalyst. Consequently,s acrificial systems consume af uel to produce H 2 while electrochemical systems only consume electricity (that is now being increasingly produced in as ustainable manner). Indeed, the electrode can both accept and donate electrons.N oi rreversible reactions take place at this step,a nd the protons are supplied from the solution.Metallocenes appear as an attractive class of molecules capable of achieving the complex photogeneration of H 2 by themselves.Indeed, they are able to both reduce protons and undergo photoactivation. Therefore,t hese "all-in-one" molecules would offer an interesting alternative to state-ofthe-art multicomponent photosystems as fewer electron transfer steps are involved. Moreover,they are simple,easily synthesized molecules,w ith ligands and metal centers that may be tuned to obtain certain desired properties,s uch as tailored solubility,a bsorbance wavelength, or redox potentials.Recently,w ed emonstrated the possibility to produce H 2 in the dark using decamethylferrocene (Cp 2 *Fe II ;C p* = C 5 Me 5 )asanelectron donor in abiphasic system.[4] Motivated by these early findings,weset out to explore the reactivity of other metallocenes as suitable electron donors.I nterestingly, both osmocene (Cp 2 Os II ;C p = C 5 H 5 ) [5] and decamethylosmocene (Cp 2 *Os II ) [6] demonstrated the capability to produce H 2 upon light irradiation. Other works have proposed the use of asingle molecule to achieve photogeneration of H 2 . Fore xample,C ole-Hamilton [7] reported ap latinum phosphine compound, while both Miller [8] and Gray [9] used iridium chloride complexes.Herein, we report Cp 2 *Ru II as the first metallocene capable of perfo...

The discrete nature of the charge carriers at polarised soft interfaces yields sharp potential profiles as well as concentration and potential independent capacitances.

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All redox flow batteries suffer from low energy storage density in comparison with conventional Li-ion batteries. However, this issue can be mitigated by utilization of solid energy storage materials to enhance the energy storage capacity. In this paper we demonstrate the utilization of copper hexacyanoferrate (CuHCF) Prussian blue analogue for this purpose, coupled with N,N,N-2,2,6,6-heptamethylpiperidinyl oxy-4-ammonium chloride (TEMPTMA) as a soluble redox mediator to target the redox transitions of the solid material. In this case, indirect charging and discharging of a solid material suspended in the electrolyte by electrochemically oxidized/reduced TEMPTMA was observed by chronoamperometry.Secondly, electrochemistry of different CuHCF composites with carbon black and multi-walled carbon nanotubes investigated, highlighting that the high conductivity of the solid energy storage materials is crucial to access the maximal charge storage capacity of the solid material.Finally, a CuHCF-TEMPTMA/Zn aqueous redox flow battery achieved stable cycling performances with high coulombic efficiency of 95% and volumetric capacity of 350 C mL -1 .