Xiaochen Zhao

Catalytic Transformation of Lignin for the Production of Chemicals and Fuels.

and Fuels Changzhi Li,† Xiaochen Zhao,† Aiqin Wang,† George W. Huber,†,‡ and Tao Zhang*,† †State Key Laborotary of Catalysis, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China ‡Department of Chemical and Biological Engineering, University of WisconsinMadison, Madison, Wisconsin 53706, United States

Macroporous ‘bubble’ graphene film via template-directed ordered-assembly for high rate supercapacitors

A three-dimensional bubble graphene film, with controllable and uniform macropores and tailorable microstructure, was fabricated by a facile hard templating strategy and exhibit extraordinary electrochemical capacitance with high rate capability (1.0 V s(-1)).

Dual-heteroatom-modified ordered mesoporous carbon: Hydrothermal functionalization, structure, and its electrochemical performance

The diverse applications of ordered mesoporous carbons (OMCs) are not only bonded to their superior structural properties, but also to their chemical properties. The termination of graphene sheets in OMCs provides abundant sites for heteroatom decoration to mediate their chemical properties. In this contribution, boron and phosphorus were co-incorporated into OMCs via a facile aqueous self-assembly taking advantage of a hydrothermal doping strategy. The as-obtained B/P-modified OMCs process a large surface area of ca. 600 m2 g−1, and a uniform pore size of ca. 6.3 nm, as well as long range ordering. By varying the hydrothermal synthesis temperature, the concentration of B and P introduced can be controlled from 0.8 to 1.6 wt% and from 2.3 to 3.6 wt%, respectively. The interaction of heteroatom B and P was enhanced when the hydrothermal temperature is above 100 °C. The heteroatom-containing groups were firmly embedded and homogeneously distributed on the carbon frameworks. When the B/P co-modified OMCs were applied as electrodes in supercapacitors, they presented promising performance compared with B- or/and P-modified OMC obtained without hydrothermal treatment.

Chemically derived graphene-metal oxide hybrids as electrodes for electrochemical energy storage: pre-graphenization or post-graphenization?

The introduction of a secondary phase is an efficient and effective way to improve the electrochemical performance of graphene towards energy storage applications. Two fundamental strategies including pre-graphenization and post-graphenization were widely employed for graphene-based hybrids. However, there is still an open question of which way is better. In this contribution, we investigated the differences in the structure and electrochemical properties of pre- and post-graphenized graphene-SnO2 hybrids. The pre-graphenization is realized by synthesis of thermally reduced graphene and subsequent impregnation of SnO2, while the post-graphenization is realized by introducing a Sn-containing phase onto GO sheets followed by chemical reduction. The pre-graphenization process provides a large amount of pores for ion diffusion, which is of benefit for loading of SnO2, fast ion diffusion for supercapacitors, and higher capacity for Li-ion batteries, but poor stability, while the post-graphenization process offers compact graphene and good interaction between the SnO2 and graphene, which provides stable structure for long term stability for supercapacitor and Li-ion battery use.

Hydrogenolysis of Glycerol to 1,3-propanediol under Low Hydrogen Pressure over WOx -Supported Single/Pseudo-Single Atom Pt Catalyst.

Single/pseudo-single atom Pt catalyst was prepared on mesoporous WOx . The large surface area and abundant oxygen vacancies of WOx improve the Pt dispersion and stabilize the Pt isolation. This newly prepared catalyst exhibited outstanding hydrogenolysis activity under 1 MPa H2 pressure with a very high space-time yield towards 1,3-propanediol (3.78 g gPt (-1)  h(-1) ) in Pt-W catalysts. The highly isolated Pt structure is thought to contribute to the excellent H2 dissociation capacity over Pt/WOx . The high selectivity towards 1,3-propanediol is attributed to the heterolytic dissociation of H2 at the interface of Pt and WOx (providing specific Brønsted acid sites and the concerted dehydration-hydrogenation reaction) and the bond formation between glycerol and WOx , which favors/stabilizes the formation of a secondary carbocation intermediate as well as triggers the redox cycle of the W species (W(6+) ⇄W(5+) ).

Selective aldol condensation of biomass-derived levulinic acid and furfural in aqueous-phase over MgO and ZnO

The aldol condensation of furfural with levulinic acid in the aqueous phase was investigated over a series of solid catalysts, including oxides (MgO, ZnO, TiO2, ZrO2, MgO–Al2O3, CeO2, Nb2O5, SnO2, and WO3) and acidic zeolites (HY, Hβ, HZSM-5, H-MOR, and SAPO-34). Two isomeric condensation products, β- and δ-furfurylidenelevulinic acids (β- and δ-FDLA), were produced after acidification. MgO and ZnO were evaluated as active and selective catalysts with respect to aqueous phase aldol condensation. MgO gave a high selectivity towards δ-FDLA due to the water-tolerant basicity. In contrast, ZnO was highly selective towards β-FDLA, indicative of an acid-catalyzed aldol reaction mechanism. Nano-ZnO with a relatively high surface area gave rise to enhanced yields of β-FDLA. In-depth investigations revealed that the exposed surface hydroxyl groups on ZnO worked as active sites for the aldol reaction.

Selective Hydrogenolysis of Glycerol to 1,3‐Propanediol: Manipulating the Frustrated Lewis Pairs by Introducing Gold to Pt/WOx

A highly dispersed Au and Pt catalyst supported on WOx was developed for high performance in the selective hydrogenolysis of glycerol to 1,3-propanediol (1,3-PD) under very mild reaction conditions (81.4 % glycerol conversion, 51.6 % 1,3-PD selectivity at 413 K, 1 MPa H2 ). The highly dispersed Au decreased the original surface Lewis-acid sites on Pt/WOx but greatly increased its in situ generated Brønsted-acid sites with the assistance of H2 through the formation of frustrated Lewis pairs. These in situ formed and spatially separated pairs of H+ and H- function as the active sites in glycerol conversion to 1,3-PD.

Porous carbon in catalytic transformation of cellulose

The application of porous carbon in catalytic transformation of cellulose has received considerable interest owing to increasing energy and environmental pressures. In this mini-review, we first outline the featured properties of porous carbon in catalytic cellulose transformation in terms of porosities and surface functionalities. An interconnected hierarchical structure and enrichment of mesopores are highly desired for reactant, intermediate, and product diffusion; while hydrophilic surfaces are favored in aqueous phase transformation and certain acidic oxygen functionalities play a role of acid sites as well as enhancing the adsorption of feedstock via 1,4-glycosidic bonds. We then summarize specific reactions in cellulose transformation in the order of hydrolysis and hydrolytic hydrogenation. In the hydrolysis of cellulose, porous carbon is generally used as a solid acid by taking advantage of its enriched oxygen functionalities, while in the hydrolytic hydrogenation, carbon serves as the support of bifunctional catalysts with active acidic sites. Finally, the synthesis and potential application of specific novel porous carbon materials, such as heteroatom-modified porous carbon and mesoporous carbon composites, are highlighted.

Chemocatalytic Conversion of Cellulosic Biomass to Methyl Glycolate, Ethylene Glycol, and Ethanol

Production of chemicals and fuels from renewable cellulosic biomass is important for the creation of a sustainable society, and it critically relies on the development of new and efficient transformation routes starting from cellulose. Here, a chemocatalytic conversion route from cellulosic biomass to methyl glycolate (MG), ethylene glycol (EG), and ethanol (EtOH) is reported. By using a tungsten-based catalyst, cellulose is converted into MG with a yield as high as 57.7 C % in a one-pot reaction in methanol at 240 °C and 1 MPa O2 , and the obtained MG can be easily separated by distillation. Afterwards, it can be nearly quantitatively converted to EG at 200 °C and to EtOH at 280 °C with a selectivity of 50 % through hydrogenation over a Cu/SiO2 catalyst. By this approach, the fine chemical MG, the bulk chemical EG, and the fuel additive EtOH can all be efficiently produced from renewable cellulosic materials, thus providing a new pathway towards mitigating the dependence on fossil resources.

Decorated resol derived mesoporous carbon: highly ordered microstructure, rich boron incorporation, and excellent electrochemical capacitance

Nanoarchitecturing of carbon with assembled building blocks in diverse scales with superior physical properties and tunable chemical characters is of great importance for energy storage. Therefore, exploring boron-modified ordered mesoporous carbons (OMCs) with tailorable microstructure and controllable incorporation become scientifically necessary. In this contribution, the boron-rich ordered mesoporous carbons were formed via a solvent evaporation-induced self-assembly strategy with controllable boron incorporation, tailorable microstructure, and extraordinary electrochemical capacitance. The incorporated boron content can be verified from 0 to 1.64 wt%, and the obtained B-OMCs exhibited widened potential window and enhanced specific capacitance. A maximum value of B incorporation (1.01-1.35 wt%) was detected in improving the specific capacitance (0.38-0.39 Fm-2). This is attributed to the specific oxygen chemisorption and the strengthened surface polarization accompanied with B modification. These results demonstrate the material chemistry, widen the potential applications, and in consequence allow mechanistic insight into the roles boron played for OMC textures and electrochemical activities.