Kai Tao

A nanostructured carbon with high specific surface area (SSA), tunable pore structure, superior electrical conductivity, mechanically robust framework, and high chemical stability is an important requirement for electrochemical energy storage. Porous graphene fabricated by chemical activation and liquid etching has a high surface area but very limited volume of electrochemically accessible mesopores. Herein, an effective strategy of in situ formation of hierarchically mesoporous oxide templates with small pores induced by Kirkendall diffusion and large pores attributed to evaporation of deliberately introduced volatile metal is proposed for chemical vapor deposition assembly of porous graphene frameworks (PGFs). The PGFs inherit the hierarchical mesoporous structure of the templates. A high SSA of 1448 m² g⁻¹, 91.6% of which is contributed by mesopores, and a mesopore volume of 2.40 cm³ g⁻¹ are attained for PGFs serving as reservoirs of ions or active materials in electrochemical energy storage applications. When the PGFs are applied in lithium-sulfur batteries, a very high sulfur utilization of 71% and a very low fading rate of ≈0.04% per cycle after the second cycle are achieved at a current rate of 1.0 C. This work provides a general strategy for the rational construction of mesoporous structures induced by a volatile metal, with a view toward the design of hierarchical nanomaterials for advanced energy storage.

Porous graphene frameworks (PGFs) are fabricated on hierarchically mesoporous oxide templates with small pores induced by Kirkendall diffusion and large pores attributed to evaporation of a deliberately introduced volatile metal. A high specific surface area of 1448 m² g⁻¹ and large mesopore volume of 2.40 cm³ g⁻¹ are attained for PGFs serving as reservoirs of ions or active materials in lithium-sulfur batteries.

The hydrogenation of furfural to furfuryl alcohol was performed in the presence of a Co/SBA-15 catalyst. High selectivity (96 %) at a conversion higher than 95 % is reported over this catalytic system. As the conversion of furfural to furfuryl alcohol occurs over metallic Co sites, the effect of reduction temperature, H₂ pressure, and reaction temperature were studied. Optimum reaction conditions were: 150 °C, 1.5 h, 2.0 MPa of H₂. The catalyst was recyclable, and furfuryl alcohol was recovered with a purity higher than 90 %. The effect of the solvent concentration was also studied. With a minimum of 50 wt % of solvent, the selectivity to furfuryl alcohol and the conversion of furfural remained high (both over 80 %). Likewise, the activity of the catalyst is maintained even in pure furfural, which confirms the real potential of the proposed catalytic system. This catalyst was also used in the hydrogenation of levulinic acid to produce γ-valerolactone selectively.

The fast and the furfural: Furfuryl alcohol is produced from furfural with a yield of 88 % in the presence of a recyclable and stable Co/SBA-15 catalyst at 150 °C under H₂ pressure in ethanol. This catalyst is also active and selective in the hydrogenation of levulinic acid to γ-valerolactone.