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Single-atom catalysts (SACs) have become an emerging frontier trend in the field of heterogeneous catalysis due to their high activity, selectivity and stability. SACs could greatly increase the availabilities of the active metal atoms in many catalytic reactions by reducing the size to single atom scale. Graphene-supported metal SACs have also drawn considerable attention due to the unique lattice structure and physicochemical properties of graphene, resulting in superior activity and selectivity for several chemical reactions. In this paper, we review recent progress in the fabrications, advanced characterization tools and advantages of graphene-supported metal SACs, focusing on their applications in catalytic reactions such as CO oxidation, the oxidation of benzene to phenol, hydrogen evolution reaction, methanol oxidation reaction, oxygen reduction reaction, hydrogenation and photoelectrocatalysis. We also propose the development of SACs towards industrialization in the future.

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Eu-zinc oxide (ZnO) has been fabricated on a p-diamond substrate by a hydrothermal technique. Efficient Eu-ZnO/diamond visible light emission is observed in the electroluminescence process. The mechanism for the energy transfer behavior and the emissions is discussed.Semiconductors doped with rare earth (RE) elements have attracted much attention in recent years due to their novel optical properties and promising applications in many elds, such as ber ampliers, light emitting devices and uorescent lamps. 1-4 In most of these applications, efficient energy transfer from the host to the RE 3+ is desired. ZnO with a band gap of 3.37 eV and a bound exciton energy of 60 meV is also an important semiconductor for which UV and visible emissions are widely reported. 5 Unfortunately, the work of harvesting intense Eu 3+ emission from ZnO lms, ceramics, and powders remains disappointing because of the strong quenching effect of the wide-band, self-activated, green or yellow emissions and the higher energy-level position of Eu 3+ relative to the bottom conduction band (CB). 6 It has been established that direct ZnO / Eu 3+ energy transfer seems physically impossible, as the radiative and nonradiative decay of excitons in ZnO are >10 2 times faster than the energy-transfer rate of RE 3+ . Fortunately, energy transfer can be facilitated by the presence of intrinsic or extrinsic defects as energy trap centers in various systems, such as ZnO/diamond, 7 which suggests that the introduction of an appropriate trap center is crucial for efficient ZnO / Eu 3+ energy transfer. Several groups have reported that defects, either intrinsic or extrinsic, can serve as the energy trapping centers to facilitate energy transfer and relevant light emission. Park et al. indicated that extrinsic defects like chlorine impurities can assist the red emission in Eu 3+ -doped ZnO. 8 Wang et al. reported the surface defects may act to help the process of energy transfer from ZnO to Eu 3+ ions. 9 Zeng et al. indicated that in Eu-doped ZnO microspheres Eu 2+ ions act as the trapping centers and transfer energy to Eu 3+ ions, leading to the emission. 10In this work, nanostructural Eu doped n-ZnO on p-type diamond has been fabricated to research the current-voltage (I-V), electroluminescence (EL) and photoluminescence (PL) properties. For the rst time, efficient Eu-ZnO/diamond visible light emission was observed. The Eu-ZnO/diamond has been realized with good rectifying behavior. By rst-principles calculation, it is demonstrated that the doped Eu atoms are favorable to the octahedral interstice in ZnO lattice.The polycrystalline diamond lm is deposited on Si wafer by hot lament CVD system. 11 Boron source of diborane or trimethylborate was additionally introduced to the reaction gases of methane/hydrogen (CH 4 /H 2 ). Before the hydrothermal process, a ZnO seed layer was deposited by radio frequency (at 13.56 MHz) magnetron sputtering process. For the hydrothermal growth, the aqueous solution of zinc acetate dihydrate and hexamethylenetetramine ...

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