homogeneous phase occur via an "Interaction of 2 M-O units" (I2M) might still be able to carry out the catalytic water oxidation reaction at the surface of an electrode, but will need to proceed through higher energy pathways that can lead to catalyst degradation. 6 Further, given the intrinsic high energy demands for the water oxidation catalysis, it is essential that the anchoring groups that act as an interface between the catalysts and surface are oxidatively resistant.Here on, we report new hybrid materials consisting of molecular WOCs anchored onto Multi-Walled Carbon Nanotubes (MWCNTs) via π-stacking interactions. 9 The resulting materials are extremely stable and allow the anchoring of a large amount of catalyst giving Turnover Numbers (TNs) over a million without apparent deactivation.In a recent publication, 10 we have reported the synthesis of complex {Ru II (tda)(py)2}, 1a, (for a drawing of tda 2-see Scheme 1) and have shown that in its high oxidation states (IV) acts as a precursor for the formation of {Ru V (O)(tda)(py)2} + . The latter is the most powerful molecular water oxidation catalyst described to date achieving Turnover Frequencies (TOF) in the range of 50.000 s -1 . In addition, we showed that the rate determining step for the water oxidation reaction is the O-O bond formation, which in this case occurs via WNA, as evidenced by kinetics and further supported by DFT calculations.Scheme 1. Drawing of the ligands discussed in the present work (top) and complex labelling strategy (bottom).[a]

Both global warming and limited fossil resources make the transition from fossil to solar fuels an urgent matter. In this regard, the splitting of water activated by sunlight is a sustainable and carbon‐free new energy conversion scheme able to produce efficient technological devices. The availability of appropriate catalysts is essential for the proper kinetics of the two key processes involved, namely, the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). During the last decade, ruthenium nanoparticle derivatives have emerged as true potential substitutes for the state‐of‐the‐art platinum and iridium oxide species for the HER and OER, respectively. Thus, after a summary of the most common methods for catalyst benchmarking, this review covers the most significant developments of ruthenium‐based nanoparticles used as catalysts for the water‐splitting process. Furthermore, the key factors that govern the catalytic performance of these nanocatalysts are discussed in view of future research directions.

Multielectron reductions such as the hydrogen evolution reaction (HER) play an important role in the development of nowadays energy economy. Herein, the application of the organometallic approach as synthetic method allows obtaining very small, ligand-capped but also highly active ruthenium nanoparticles (RuNPs) for the HER in both acidic and basic media. When deposited onto glassy carbon, the catalytic activity of this nanomaterial in 1 M H 2 SO 4 solution is highly dependent on the oxidation state of the NPs surface, with metallic Ru sites being clearly more active than RuO 2 ones. In sharp contrast, in 1 M NaOH as electrolyte, the original Ru/RuO 2 mixture is maintained even under reductive conditions. Estimation of surface active sites and electrochemically active surface area (ECSA) allowed benchmarking this catalytic system, confirming its leading performance among HER electrocatalysts reported at both acidic and basic pH. Thus, in 1 M NaOH condition, it displays lower overpotentials (η 0 ≈ 0 mV, η 10 = 25 mV) than those of commercial Pt/C and Ruthenium black (Rub), and also fairly outperforms them in short-and long-term stability tests. In 1 M H 2 SO 4 solution, it clearly outdoes commercial Rub and is competitive or even superior to commercial Pt/C, working at very low overpotentials (η 0 ≈ 0 mV, η 10 = 20 mV) with a Tafel slope of 29 mV•dec −1 , achieving TOFs as high as 17 s −1 at η = 100 mV and reaching a current density of |j| = 10 mA•cm −2 for at least 12 h without any sign of deactivation.

A porous Ru nanomaterial exhibits high electrocatalytic performance and excellent durability for the hydrogen evolution reaction (HER) under both acidic and neutral conditions. It displays a low overpotential of 83 mV at a current density of 10 mA cm and an excellent durability up to 12 h in 0.5 M HSO.

homogeneous phase occur via an "Interaction of 2 M-O units" (I2M) might still be able to carry out the catalytic water oxidation reaction at the surface of an electrode, but will need to proceed through higher energy pathways that can lead to catalyst degradation. 6 Further, given the intrinsic high energy demands for the water oxidation catalysis, it is essential that the anchoring groups that act as an interface between the catalysts and surface are oxidatively resistant.Here on, we report new hybrid materials consisting of molecular WOCs anchored onto Multi-Walled Carbon Nanotubes (MWCNTs) via π-stacking interactions. 9 The resulting materials are extremely stable and allow the anchoring of a large amount of catalyst giving Turnover Numbers (TNs) over a million without apparent deactivation.In a recent publication, 10 we have reported the synthesis of complex {Ru II (tda)(py)2}, 1a, (for a drawing of tda 2-see Scheme 1) and have shown that in its high oxidation states (IV) acts as a precursor for the formation of {Ru V (O)(tda)(py)2} + . The latter is the most powerful molecular water oxidation catalyst described to date achieving Turnover Frequencies (TOF) in the range of 50.000 s -1 . In addition, we showed that the rate determining step for the water oxidation reaction is the O-O bond formation, which in this case occurs via WNA, as evidenced by kinetics and further supported by DFT calculations.Scheme 1. Drawing of the ligands discussed in the present work (top) and complex labelling strategy (bottom).[a]

Electrocatalytic Nitrobenzene Hydrogenation and competitive Hydrogen Evolution Reaction (HER) have been studied, using two catalytic systems: oxidized carbon fibers (organic) and Ruthenium nanoparticles supported on unaltered carbon fibers (inorganic).

Four different cathodes for the hydrogen evolution reaction (HER) have been developed by the decoration of commercial carbon microfibers with Ru nanoparticles (Ru NPs). Two types of carbon fibers have been used: pristine, as‐received, carbon fibers (pCF) and carbon fibers modified by an oxidative treatment that led to the functionalization of their surface with carboxylic groups (fCF). The decoration of these CFs with Ru NPs has been performed by two different methodologies based on the organometallic approach: direct synthesis of Ru NPs on top of the CFs (in‐situ Ru NPs) or impregnation of the CFs with a colloidal solution of preformed Ru NPs stabilized with 4‐phenylpyridine (RuPP NPs; ex‐situ Ru NPs). The electrocatalytic performance of these four cathodes (ex‐situ RuPP@pCF and RuPP@fCF; in‐situ Ru@pCF and Ru@fCF) for the HER has been studied in acidic conditions. The results obtained show that both the nature of the NPs and of the carbon fibers play a key role on the stability and activity of the hybrid electrodes: ex‐situ prepared Ru NPs afford better activities at lower overpotentials and better stabilities than those formed in‐situ. Among the two ex‐situ systems, an enhancement of the stability with pCF is observed, that may arise from more effective π‐interactions between 4‐phenylpyridine ligand and the surface of these carbon fibers. This interaction is somehow disfavored with fCF due to the presence of the surface carboxylic groups.

Microorganisms living in hypersaline microbial mats frequently form consortia under stressful and changing environmental conditions. In this paper, the heterotrophic strain DE2010 from a microalgae consortium (Scenedesmus sp. DE2009) from Ebro Delta microbial mats has been phenotypically and genotypically characterized and identified. In addition, changes in the morphology and biomass of this bacterium in response to nitrogen deficiency stress have been evaluated by correlative light and electron microscopy (CLEM) combining differential interference contrast (DIC) microscopy and transmission electron microscopy (TEM) and scanning electron microscopy (SEM). These isolated bacteria are chemoorganoheterotrophic, gram-negative, and strictly aerobic bacteria that use a variety of amino acids, organic acids, and carbohydrates as carbon and energy sources, and they grow optimally at 27 °C in a pH range of 5 to 9 and tolerate salinity from 0 to 70‰ NaCl. The DNA-sequencing analysis of the 16S rRNA and nudC and fixH genes and the metabolic characterization highlight that strain DE2010 corresponds to the species Ochrobactrum anthropi. Cells are rod shaped, 1-3 μm in length, and 0.5 μm wide, but under deprived nitrogen conditions, cells are less abundant and become more round, reducing their length and area and, consequently, their biomass. An increase in the number of pleomorphic cells is observed in cultures grown without nitrogen using different optical and electron microscopy techniques. In addition, the amplification of the fixH gene confirms that Ochrobactrum anthropi DE2010 has the capacity to fix nitrogen, overcoming N-limiting conditions through a nifH-independent mechanism that is still unidentified.