Li-ion batteries have contributed to the commercial success of portable electronics and may soon dominate the electric transportation market provided that major scientific advances including new materials and concepts are developed. Classical positive electrodes for Li-ion technology operate mainly through an insertion-deinsertion redox process involving cationic species. However, this mechanism is insufficient to account for the high capacities exhibited by the new generation of Li-rich (Li(1+x)Ni(y)Co(z)Mn(1-x-y-z)O₂) layered oxides that present unusual Li reactivity. In an attempt to overcome both the inherent composition and the structural complexity of this class of oxides, we have designed structurally related Li₂Ru(1-y)Sn(y)O₃ materials that have a single redox cation and exhibit sustainable reversible capacities as high as 230 mA h g(-1). Moreover, they present good cycling behaviour with no signs of voltage decay and a small irreversible capacity. We also unambiguously show, on the basis of an arsenal of characterization techniques, that the reactivity of these high-capacity materials towards Li entails cumulative cationic (M(n+)→M((n+1)+)) and anionic (O(2-)→O₂(2-)) reversible redox processes, owing to the d-sp hybridization associated with a reductive coupling mechanism. Because Li₂MO₃ is a large family of compounds, this study opens the door to the exploration of a vast number of high-capacity materials.

Owing to the sluggish kinetics of the hydrogen oxidation reaction (HOR) in alkaline electrolyte, it is considered a limiting reaction for the development of anion-exchange membrane fuel cell (AEMFC) technology. Studies of alkaline HOR catalysis mainly focus on carbon-supported nanoparticles, which have weak metal–support interactions. In this contribution, we present a unique support based on transition metal carbides (TMCs = Mo2C, Mo2C–TaC, and Mo2C–W2C) for the HOR. PtRu nanoparticles are deposited onto the TMC supports and are characterized by a variety of analytical techniques. The major findings are (i) experimental and theoretical evidence for strong-metal support interaction by both X-ray absorption near-edge structure and density functional theory, (ii) the kinetic current density (j k,s) @25 mV of PtRu/Mo2C–TaC catalyst are 1.65 and 1.50 times higher than that of PtRu/Mo2C and PtRu/Mo2C–W2C, respectively, and (iii) enhanced “tethering” of PtRu nanoparticles on TMC supports. Furthermore, the AEMFC based on the PtRu/Mo2C–TaC anode exhibited a peak power density of 1.2 W cm–2 @70 °C, opening the doors for the development of advanced catalysts based on engineering support materials.

Friction and wear reduction by diamond-like carbon (DLC) in automotive applications can be affected by zinc-dialkyldithiophosphate (ZDDP), which is widely used in engine oils. Our experiments show that DLC’s tribological behaviour in ZDDP-additivated oils can be optimised by tailoring its stiffness, surface nano-topography and hydrogen content. An optimal combination of ultralow friction and negligible wear is achieved using hydrogen-free tetrahedral amorphous carbon (ta-C) with moderate hardness. Softer coatings exhibit similarly low wear and thin ZDDP-derived patchy tribofilms but higher friction. Conversely, harder ta-Cs undergo severe wear and sub-surface sulphur contamination. Contact-mechanics and quantum-chemical simulations reveal that shear combined with the high local contact pressure caused by the contact stiffness and average surface slope of hard ta-Cs favour ZDDP fragmentation and sulphur release. In absence of hydrogen, this is followed by local surface cold welding and sub-surface mechanical mixing of sulphur resulting in a decrease of yield stress and wear.