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Green synthesis has grabbed appreciable attention to eliminate the negative effects associated with various chemical processes. Due to the unparalleled electrical, mechanical, thermal and excellent physical properties, graphene, as the thinnest two-dimensional material with high surface area, has the unfathomable potential in the domain of green chemistry in terms of both synthesis and application. In this regard, we present an overview of the research progresses on the greener synthesis of graphene, including micromechanical exfoliation, chemical reduction of graphene oxide (GO), chemical vapor synthesis and popping of GO. Meanwhile, various applications of graphene pertinent to sustainable developments, such as energy storage, catalysis, electrochemistry, fuel cell, supercapacitor and biomedicine have also been highlighted.

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.

A series of metal element (Al, Fe, Mg and Ni)-doped ZnO (M-ZnO) photocatalysts have been successfully synthesized on graphene-coated polyethylene terephthalate (GPET) flexible substrate via the hydrothermal method. The effects of doped metals in ZnO were also studied on the crystal structure, morphology and photocatalytic performance. The photocatalytic experiment results indicated that, compared with Al-, Mg- and Fe-ZnO/GPET photocatalysts under ultraviolet (UV) light irradiation, Ni-ZnO/GPET had better photocatalytic activity, and the degradation rate of methylene blue (MB) was 81.17%. Meanwhile, the mechanism of enhancing the photocatalytic activity of metal element-doped ZnO is also discussed. It is concluded that, after doping with metal elements, electrons and holes are prevented from recombination by trapping electrons of the ZnO/GPET conductive band, thereby improving the photocatalytic activity.

As hydraulic fracturing technology has been widely used in the exploitation of tight gas sandstone reservoirs, the retention of hydraulic fracturing fluid will cause water locking damage to tight gas sandstone reservoirs and it can seriously affect the development of gas reservoirs. Selective injection of drying agents into tight sandstone reservoirs can effectively decrease water saturation and improve gas seepage capacity. Based on the laboratory orthogonal experiments, the injection parameters of drying agents are optimized. Results show that the improvement of gas permeability reaches its best when the concentration of the main drying agent is 1g/L, the injection volume is 4 PV, the injection rate is 0.2 mL/min, the reaction time is 70 min, the reaction temperature is 120 °C, the injection volume of post-positioning fluid is 4 PV, and the reverse displacement time is 90 min. In addition, the higher the irreducible water saturation of the tight core, the greater the increment of gas phase permeability after drying reaction and the higher the degree of water saturation reduction.

Developing highly-active single atom catalyst to realize visible light driven photocatalytic CO2 reduction into value-added chemicals is an appealing route toward utilizing CO2 as the only carbon source for a sustainable future. Herein, we have successfully synthesized the atomically dispersed manganese sites in nitrogen doped carbon via an in-situ polymerization approach. The in-situ oxidative polymerization of pyrrole monomer directly catalyzed by manganese dioxide could extract the Mn atoms from MnO2 and stabilize them within the as-generated polymer skeleton in one step. After high-temperature pyrolysis, atomically dispersed Mn sites are obtained, firmly and homogeneously anchored by the as-generated N-doped carbon support. The as obtained catalyst can act as cocatalyst to realize photocatalytic CO2 reduction to produce synthesis gas under visible light using [Ru(bpy)3]Cl2 (bpy: 2,2′-bipyridine) as photosensitizer and triethanolamine as sacrifacial agent, with gas evolution rate of CO 1470 μmol/h/g, H2 1310 μmol/h/g and tunable CO/H2 ratio from 1.12 to 0.43. Our approach is versatile to prepare a variety of morphology-controllable single atom catalysts from metal oxides for important industrial applications.