Despite the recent developments in Graphene Oxide due to its importance as a host precursor of Graphene, the detailed electronic structure and its evolution during the thermal reduction remain largely unknown, hindering its potential applications. We show that a combination of high resolution in situ X-ray photoemission and X-ray absorption spectroscopies offer a powerful approach to monitor the deoxygenation process and comprehensively evaluate the electronic structure of Graphene Oxide thin films at different stages of the thermal reduction process. It is established that the edge plane carboxyl groups are highly unstable, whereas carbonyl groups are more difficult to remove.The results consistently support the formation of phenol groups through reaction of basal plane epoxide groups with adjacent hydroxyl groups at moderate degrees of thermal activation (~400 °C). The phenol groups are predominant over carbonyl groups and survive even at a temperature of 1000 °C. For the first time a drastic increase in the density of states (DOS) near the Fermi level at 600 °C is observed, suggesting a progressive restoration of aromatic structure in the thermally reduced graphene oxide.

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Reduced graphene oxide/platinum supported electrocatalysts (Pt/RGO) were synthesized by employing a fast and eco-friendly microwave-assisted polyol process, which facilitated the simultaneous reduction of graphene oxide and formation of Pt nanocrystals. This system was tested for potential use as an anode material through the electrooxidation of methanol. Compared to the commercial carbon-supported Pt electrocatalysts, the Pt/ RGO showed an unprecedented CO poisoning tolerance, high electrochemical active surface area, and high catalytic mass activity for methanol oxidation reaction, demonstrated by increases of 110, 134, and 60%, respectively. We found that the high concentration of oxygen functional groups on reduced graphene oxide plays a major role on the removal of carbonaceous species on the adjacent Pt sites, underlining a synergetic effect between the oxygen moieties on graphene support and Pt nanoparticles. The present microwave assisted synthesis of Pt/RGO provides a new path to prepare electrocatalysts with excellent electrocatalytic activity and CO tolerance, which is of great significance in energy-related applications.

Flexible supercapacitors, a state-of-the-art material, have emerged with the potential to enable major advances in for cutting-edge electronic applications. Flexible supercapacitors are governed by the fundamentals standard for the conventional capacitors but provide high flexibility, high charge storage and low resistance of electro active materials to achieve high capacitance performance. Conducting polymers (CPs) are among the most potential pseudocapacitor materials for the foundation of flexible supercapacitors, motivating the existing energy storage devices toward the future advanced flexible electronic applications due to their high redox active-specific capacitance and inherent elastic polymeric nature. This review focuses on different types of CPs-based supercapacitor, the relevant fabrication methods and designing concepts. It describes recent developments and remaining challenges in this field, and its impact on the future direction of flexible supercapacitor materials and relevant device fabrications.

The production of renewable solar fuel through CO2 photoreduction, namely artificial photosynthesis, has gained tremendous attention in recent times due to the limited availability of fossil-fuel resources and global climate change caused by rising anthropogenic CO2 in the atmosphere. In this study, graphene oxide (GO) decorated with copper nanoparticles (Cu-NPs), hereafter referred to as Cu/GO, has been used to enhance photocatalytic CO2 reduction under visible-light. A rapid one-pot microwave process was used to prepare the Cu/GO hybrids with various Cu contents. The attributes of metallic copper nanoparticles (∼4-5 nm in size) in the GO hybrid are shown to significantly enhance the photocatalytic activity of GO, primarily through the suppression of electron-hole pair recombination, further reduction of GO's bandgap, and modification of its work function. X-ray photoemission spectroscopy studies indicate a charge transfer from GO to Cu. A strong interaction is observed between the metal content of the Cu/GO hybrids and the rates of formation and selectivity of the products. A factor of greater than 60 times enhancement in CO2 to fuel catalytic efficiency has been demonstrated using Cu/GO-2 (10 wt % Cu) compared with that using pristine GO.

Band gap opening and engineering is one of the high priority goals in the development of graphene electronics. Here, we report on the opening and scaling of band gap in BN doped graphene (BNG) films grown by low-pressure chemical vapor deposition method. High resolution transmission electron microscopy is employed to resolve the graphene and h-BN domain formation in great detail. X-ray photoelectron, micro-Raman, and UV-vis spectroscopy studies revealed a distinct structural and phase evolution in BNG films at low BN concentration. Synchrotron radiation based XAS-XES measurements concluded a gap opening in BNG films, which is also confirmed by field effect transistor measurements. For the first time, a significant band gap as high as 600 meV is observed for low BN concentrations and is attributed to the opening of the π-π* band gap of graphene due to isoelectronic BN doping. As-grown films exhibit structural evolution from homogeneously dispersed small BN clusters to large sized BN domains with embedded diminutive graphene domains. The evolution is described in terms of competitive growth among h-BN and graphene domains with increasing BN concentration. The present results pave way for the development of band gap engineered BN doped graphene-based devices.

Cathodoluminescence ͑CL͒ spectroscopy has been employed to study the electronic and optical properties of well-aligned ZnO nanorods with diameters ranging from 50 to 180 nm. Single-nanorod CL studies reveal that the emission peak moves toward higher energy as the diameter of the ZnO nanorod decreases, despite that their sizes are far beyond the quantum confinement regime. Blueshift of several tens of meV in the CL peak of these nanorods has been observed. Moreover, this anomalous energy shift shows a linear relation with the inverse of the rod diameter. Possible existence of a surface resonance band is suggested and an empirical formula for this surface effect is proposed to explain the size dependence of the CL data.

The development of suitable approaches for the synthesis of ultrathin transition-metal dichalcogenide (TMD) catalysts is required to engineer phases, intercoupling between different phases, in-plane defects, and edges and hence maximize their catalytic performance for hydrogen production. In this work, we report a simple one-step hydrothermal approach for the synthesis of a three-dimensional (3D) network of self-assembled metallic MoS2/MoO3 nanosheets, using α-MoO3 and thiourea (TU) as the Mo and S precursors, respectively. A systematic structural/property relationship study, while varying the precursors’ molar concentration ratios (TU/MoO3) and reaction temperatures (T R), revealed a kinetically controlled regime, in hydrothermal synthesis, that enabled the formation of ultrathin branched MoS2/MoO3 nanosheets with the highest metallic content of ∼47 % in a reproducible manner. Importantly, the work established that in addition to the rich metallic MoS2 phase (1T), the electronically coupled interfaces between MoO3 and MoS2 nanodomains, profusion of active sites, and tuned electrical conductivity significantly contributed to hydrogen evolution reaction (HER)-catalytic activity, affording a low overpotential of 210 mV (with respect to the reversible hydrogen electrode) at a current density of 10 mA/cm2, a small Tafel slope of ∼50 mV/dec, and high stability. Overall, this work demonstrated a controllable one-step hydrothermal method for the rational design and synthesis of a 3D network of MoS2/MoO3 nanosheets with high 1T-MoS2 metallic yield, simultaneous incorporation of MoO3/MoS2 heterointerfaces, sulfur vacancies, and tuned electrical conductivity, which are highly beneficial for clean energy conversion applications that can potentially be expanded to other two-dimensional TMD materials.