In this study, we highlight that surface nitrogen-injection engineering brings a high formation rate for CO 2 reduction to formate, which is high level among the reported electrocatalysts. Surface nitrogeninjection engineering can increase the amounts of active sites and optimize the electronic structure simultaneously. Taking an example of SnS 2 precursors, the final-obtained surface N-enriched Sn(S) nanosheets (denoted as N−Sn(S) nanosheets) exhibit a 5-fold of current density and 2.45-fold of Faradaic efficiency than pristine SnS 2 derived Sn(S) nanosheets (denoted as Sn(S) nanosheets). On account of high activity and selectivity, the formation rate of formate is 14 times than that of pristine samples and reaches up to 1358 μmol h −1 cm −2 . Moreover, this strategy is proven to be general to other metal sulfides, such as CuS and In 2 S 3 . We anticipate that surface nitrogeninjection engineering offers new avenues to rational design of advanced electrocatalysts for CO 2 reduction reaction.

Auxetic two-dimensional (2D) materials provide a promising platform for biomedicine, sensors, and many other applications at the nanoscale. In this work, utilizing a hypothesis-based data-driven approache, we identify multiple materials with remarkable in-plane auxetic behavior in a family of buckled monolayer 2D materials. These materials are transition metal selenides and transition metal halides with the stoichiometry MX (M = V, Cr, Mn, Fe, Co, Cu, Zn, Ag, and X = Se, Cl, Br, I). First-principles calculations reveal that the desirable auxetic behavior of these 2D compounds originates from the interplay between the buckled 2D structure and the weak metal–metal interaction determined by their electronic structures. We observe that the Poisson’s ratio is sensitive to magnetic order and the amount of uniaxial stress applied. A transition from positive Poisson’s ratio (PPR) to negative Poisson’s ratio (NPR) for a subgroup of MX compounds under large uniaxial stress is predicted. The work provides a guideline for the future design of 2D auxetic materials at the nanoscale.

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Electron correlation effects among 4d-electrons are generally believed to be weak due to a large spatial extension of 4d-orbitals and then long neglected in studying the electronic and adsorption properties of transition-metal oxide catalysts. Here we demonstrate that the electron correlation plays a critical role in improving the catalytic activity of ruthenium oxides towards oxygen evolution reaction (OER). Density functional theory plus Hubbard U calculations on the state of the-art OER catalyst, rutile RuO2, reveal that the adsorption energies for oxygenated intermediates can be nearly optimized when the metallic oxide turns into a Mott insulator. By regulating the effective electron correlations via RuO6 octahedral network in nanosized various rutile and pyrochlore ruthenium oxides, we successfully realize a Mott metal-insulator transition and develop a series of insulating oxides with a superior OER performance to the metallic RuO2. Our work builds a bridge between the electrochemistry and Mott physics for transition-metal oxides, opening a new avenue for designing advanced catalysts.

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