The cost effective synthesis and patterning of carbon nanomaterials is a challenge in electronic and energy storage devices. Here we report a one-step, scalable approach for producing and patterning porous graphene films with three-dimensional networks from commercial polymer films using a CO₂ infrared laser. The sp³-carbon atoms are photothermally converted to sp²-carbon atoms by pulsed laser irradiation. The resulting laser-induced graphene (LIG) exhibits high electrical conductivity. The LIG can be readily patterned to interdigitated electrodes for in-plane microsupercapacitors with specific capacitances of >4 mF cm⁻² and power densities of ~9 mW cm⁻². Theoretical calculations partially suggest that enhanced capacitance may result from LIG’s unusual ultra-polycrystalline lattice of pentagon-heptagon structures. Combined with the advantage of one-step processing of LIG in air from commercial polymer sheets, which would allow the employment of a roll-to-roll manufacturing process, this technique provides a rapid route to polymer-written electronic and energy storage devices.

Ultrathin transition metal dichalcogenides (TMDCs) of Mo and W show great potential for digital electronics and optoelectronic applications. Whereas early studies were limited to mechanically exfoliated flakes, the large-area synthesis of 2D TMDCs has now been realized by chemical vapor deposition (CVD) based on a sulfurization reaction. The optoelectronic properties of CVD grown monolayer MoS₂ have been intensively investigated, but the influence of stoichiometry on the electrical and optical properties has been largely overlooked. Here we systematically vary the stoichiometry of monolayer MoS₂ during CVD via controlled sulfurization and investigate the associated changes in photoluminescence and electrical properties. X-ray photoelectron spectroscopy is employed to measure relative variations in stoichiometry and the persistence of MoO_x species. As MoS_2−δ is reduced (increasing δ), the field-effect mobility of monolayer transistors increases while the photoluminescence yield becomes nonuniform. Devices fabricated from monolayers with the lowest sulfur content have negligible hysteresis and a threshold voltage of ∼0 V. We conclude that the electrical and optical properties of monolayer MoS₂ crystals can be tuned via stoichiometry engineering to meet the requirements of various applications.

Water electrolysis is a very promising technology for sustainable hydrogen generation using renewable electrical energy. The excellent performance and dynamic behavior for storing electrical energy in hydrogen allow polymer electrolyte membrane (PEM) electrolysis to cover the gap between the intermittent renewable power production and the grid demand at different time horizons and scales. This work is addressed to the development and characterization of high performance nanostructured Ir-Ru-oxide electro-catalyst achieving for the rate determining oxygen evolution reaction a current density of 3 A cm−2 at about 1.8 V (> 80% enthalpy efficiency) with a low catalyst loading (0.34 mg cm−2). The stability characteristics were studied in practical PEM electrolysis cells operating at 80 °C, using several durability tests of 1000 h each to evaluate the reliability of this electro-catalyst for real-life operation. Further insights on the degradation mechanism were acquired by subjecting the catalyst to potential steps in a specially designed electrochemical flow cell under corrosive liquid electrolyte with on-line monitoring of the dissolved ions. Structural, morphology, composition and surface analysis of the anode electro-catalyst after operation in the electrolysis cell, complemented by in-situ electrochemical diagnostics, provided important insights into the degradation mechanisms. Catalyst operation at high turnover frequency (TOF) was observed to cause a progressive change of Lewis acidity characteristics with time for both Ir and Ru cations thus influencing their ability to promote water oxidation.

Despite the fact that the methanol synthesis process includes industrially some of the most important catalytic chemical reactions, it is still not clear how different gaseous species impact catalyst component structure. With the goal to reduce CO2 emissions through hydrogenation to CH3OH, a higher H2O formation rate than in the production from compressed CO-rich feed should also be considered. It is known that steam accelerates the sintering of metals, several oxide compounds and their interfaces. To determine the effect of moisture on the Cu/ZnO/Al2O3 catalysts, a commercial catalytic material was systematically aged at various gas compositions and analyzed using transient H2 surface adsorption, N2O pulse efficient chemisorption, X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM) mapping (EDX), X-ray powder diffraction (XRD) and N2 physisorption, and the mechanisms of deactivation were observed. A strong consistent relation between the compacting of Al2O3, the amount of water in controlled stream flow and activity was found. This connected loss of support resulted in the (re)forming of Cu, ZnO and Cu/ZnO phases. Copper particle growth was modeled by applying physical coalescence model. In the presence of CO or/and CH3OH, zinc oxide material started to cover Cu granules, while H2O promoted the development of separate Cu regions.

Gold–copper (Au–Cu) phases were employed already by pre-Columbian civilizations, essentially in decorative arts, whereas nowadays, they emerge in nanotechnology as an important catalyst. The knowledge of the phase diagram is critical to understanding the performance of a material. However, experimental determination of nanophase diagrams is rare because calorimetry remains quite challenging at the nanoscale; theoretical investigations, therefore, are welcomed. Using nanothermodynamics, this paper presents the phase diagrams of various polyhedral nanoparticles (tetrahedron, cube, octahedron, decahedron, dodecahedron, rhombic dodecahedron, truncated octahedron, cuboctahedron, and icosahedron) at sizes 4 and 10 nm. One finds, for all the shapes investigated, that the congruent melting point of these nanoparticles is shifted with respect to both size and composition (copper enrichment). Segregation reveals a gold enrichment at the surface, leading to a kind of core–shell structure, reminiscent of the historical artifacts. Finally, the most stable structures were determined to be the dodecahedron, truncated octahedron, and icosahedron with a Cu-rich core/Au-rich surface. The results of the thermodynamic approach are compared and supported by molecular-dynamics simulations and by electron-microscopy (EDX) observations.