A nanostructured, carbon-based physical catalyst electrochemically reduces N2 to ammonia under ambient conditions.

Though carbon dioxide is a waste product of combustion, it can also be a potential feedstock for the production of fine and commodity organic chemicals provided that an efficient means to convert it to useful organic synthons can be developed. Herein we report a common element, nanostructured catalyst for the direct electrochemical conversion of CO 2 to ethanol with high Faradaic efficiency (63 % at À1.2 V vs RHE) and high selectivity (84 %) that operates in water and at ambient temperature and pressure. Lacking noble metals or other rare or expensive materials, the catalyst is comprised of Cu nanoparticles on a highly textured, N-doped carbon nanospike film. Electrochemical analysis and density functional theory (DFT) calculations suggest a preliminary mechanism in which active sites on the Cu nanoparticles and the carbon nanospikes work in tandem to control the electrochemical reduction of carbon monoxide dimer to alcohol.

2D PtSSe for photocatalytic water splitting under visible or infrared light.

Direct laser-reduction of graphene oxide (GO), as a lithography-free approach, has been proven effective in manufacturing in-plane micro-supercapacitors (MSCs) with fast ion diffusion.

MXenes, a family of two-dimensional transition-metal carbides, were successfully demonstrated as co-catalysts with rutile TiO2 for visible-light-induced solar hydrogen production from water splitting. The physicochemical properties of Ti3 C2 Tx MXene coupled with TiO2 were investigated by a variety of characterization techniques. The effect of the Ti3 C2 Tx loading on the photocatalytic performance of the TiO2 /Ti3 C2 Tx composites was elucidated. With an optimized Ti3 C2 Tx content of 5 wt %, the TiO2 /Ti3 C2 Tx composite shows a 400 % enhancement in the photocatalytic hydrogen evolution reaction compared with that of pure rutile TiO2 . We also expanded our exploration to other MXenes (Nb2 CTx and Ti2 CTx ) as co-catalysts coupled with TiO2 , and these materials also exhibited enhanced hydrogen production. These results manifest the generality of MXenes as effective co-catalysts for solar hydrogen production.

Two-dimensional auxetic materials have attracted considerable attention due to their potential applications in medicine, tougher composites, defense, and so on. However, they are scare especially at low dimension, as auxetic materials are mainly realized in engineered materials and structures. Here, using first-principles calculations, we identify a compelling two-dimensional auxetic material, single-layer Ag2S, which possesses large negative Poisson’s ratios in both in-plane and out-of-plane directions, but anisotropic ultralow Young’s modulus. Such a coexistence of simultaneous negative Poisson’s ratios in two directions is extremely rare, which is mainly originated from its particular zigzag-shaped buckling structure. In addition, contrary to the previously known metal-shrouded single-layer M2X (M = metal, X = nonmetal), single-layer Ag2S is the first nonmetal-shrouded M2X. Electronic calculations show that it is an indirect-gap semiconductor with gap value of 2.83 eV, and it can be turned to be direct with strain. These intriguing properties make single-layer Ag2S a promising auxetic material in electronics and mechanics.

Two-dimensional valleytronic systems can provide information storage and processing advantages that complement or surpass those of conventional charge- and spin-based semiconductor technologies. The major challenge currently is to realize valley polarization for manipulating the valley degree of freedom. Here, we propose that valley polarization can be readily achieved in Janus single-layer MoSSe through magnetic doping, which is highly feasible in experiment. Due to inversion symmetry breaking combined with strong spin-orbit coupling (SOC), the pure single-layer MoSSe harbors an intriguing multivalleyed band structure and strong coupled spin and valley physics. After doping Cr/V, the long-sought valley polarization is successfully achieved with a remarkable energy difference of ∼0.06 eV upon switching on SOC. Furthermore, the valley polarization in Cr/V-doped single-layer MoSSe is tunable via strain engineering. Our work thus provides a promising platform for experimental studies and applications of the valleytronics.

Hydrogen production through facile photocatalytic water splitting is regarded as a promising strategy to solve global energy problems. Transition-metal carbides (MXenes) have recently drawn attention as potential co-catalyst candidates for photocatalysts. Here, we report niobium pentoxide/carbon/niobium carbide (MXene) hybrid materials (Nb O /C/Nb C) as photocatalysts for hydrogen evolution from water splitting. The Nb O /C/Nb C composites were synthesized by one-step CO oxidation of Nb CT . Nb O grew homogeneously on Nb C after mild oxidation, during which some amorphous carbon was also formed. With an optimized oxidation time of 1.0 h, Nb O /C/Nb C showed the highest hydrogen generation rate (7.81 μmol h g ), a value that was four times higher than that of pure Nb O . The enhanced performance of Nb O /C/Nb C was attributed to intimate contact between Nb O and conductive Nb C and the separation of photogenerated charge carriers at the Nb O /Nb C interface; the results presented herein show that transition-metal carbide are promising co-catalysts for photocatalytic hydrogen production.