Hierarchical nitrogen-doped porous graphene/carbon (NPGC) composites were fabricated by a simple and nontemplate method. The morphology characterizations demonstrate that reduced graphene oxide was successfully coated by the carbon derived from glucose, and a well-organized and interpenetrated hierarchical porous structure of NPGC was formed after pyrolysis at 950 °C. Notably, the prepared material, denoted as NPGC-950, has superlarge specific surface area (1510.83 m(2) g(-1)) and relatively high content percentage of pyridinic and graphitic nitrogen. As an efficient metal-free electrocatalyst, NPGC-950 exhibits a high onset potential (0.91 V vs RHE) and a nearly four-electron pathway for oxygen reduction reaction in alkaline solution as well as stronger methanol tolerance and better long-term durability than commercial Pt/C. In view of these excellent features, the obtained hierarchical N-doped metal-free porous carbon material is a promising catalyst for oxygen reduction reaction and could be widely applied in industry.
Electrochemical depolymerization of lignin for production of renewable aromatic compounds is presented.In the designed non-diaphragm electrolytic cell, lignin in alkaline electrolyte was directly electro-oxidized on the anode and chemically oxidized by the electro-generated H 2 O 2 formed on the cathode simultaneously. The linkages among C9 units in lignin were broken down and more than 20 kinds of low-molecular-weight (LMW) aromatic compounds containing hydroxyl, aldehyde, carbonyl and carboxyl groups were generated and identified by GC-MS and ESI-MS/MS measurements. The effects of electrolysis conditions on the concentration of H 2 O 2 , the decomposition rate of H 2 O 2 into reactive oxygen species (ROS) and the yields of LMW products were investigated in detail. Results show that H 2 O 2 and ROS play very important roles in lignin depolymerization. The electrolysis conditions for producing higher concentrations of H 2 O 2 and ROS are in favor of giving higher yields of LMW products.59.2% of lignin was depolymerized into LMW products after 1 hour-electrolysis at 80 C under a current density of 8 mA cm À2 with extra O 2 supplement.
Lignin-based phosphate melamine was used as a partial substitute for polyols to synthesize rigid polyurethane foams which exhibit high mechanical strength and low flammability.
Although N-doped graphene-based electrocatalysts have shown good performance for oxygen reduction reaction (ORR), they still suffer from the single-type active site in the as-prepared catalyst, limited accessible active surface area because of easy aggregation of graphene, and harsh condition for preparation process of graphene. Therefore, further developing a novel type of graphene-based electrocatalyst by a facile and environmentally benign method is highly anticipated. Herein, we first fabricate a sandwich-like graphene/carbon hybrid using graphene oxide (GO) and nontoxic starch. Then the graphene/carbon hybrid undergoes postprocessing with iron(III) chloride (FeCl3) and potassium sulfocyanide (KSCN) to acquire N-doped graphene/carbon nanosheets decorated by Fe and S. The resultant displays the features of interpenetrated three-dimensional hierarchical architecture composed of abundant sandwich-like graphene/carbon nanosheets and low graphene content in as-prepared sample. Remarkably, the obtained catalyst possesses favorable kinetic activity due to the unique structure and synergistic effect of N, S, and Fe on ORR, showing high onset potential, low Tafel slope, and nearly four-electron pathway. Meanwhile, the catalyst exhibits strong methanol tolerance and excellent long-term durability. In view of the multiple active sites, unique hierarchical structure, low graphene content, and outstanding electrochemical activity of the as-prepared sample, this work could broaden the thinking to develop more highly efficient graphene/carbon electrocatalysts for ORR in fuel cells.
Nickel/iron (NiÀFe)-based compounds are known as active electrocatalysts for the oxygen evolution reaction (OER), which plays an important role in metalÀair batteries and water splitting. Herein, a three-dimensional (3D) porous nickel foam electrode (NiFe(OH) x NSs/Ni f ) modified with NiÀFe hydroxide nanosheets (NSs) is prepared by using a fast and facile electrodeposition method. The electrode is subsequently applied in the electrolysis of Na 2 CO 3 /NaHCO 3 to produce hydrogen, oxygen, NaOH, and NaHCO 3 /CO 2 . By carefully controlling the electrodeposition time, ultrathin NiFe(OH) x NSs with a thickness of approximately 2-6 nm are interlaced with one another and grown vertically on nickel foam to form a hierarchical composite electrode. The prepared NiFe(OH) x NSs/Ni f electrode exhibits superb OER performance with an overpotential of 260 mV at 10 mA cm À2 and a low Tafel slope of 29 mV dec À1 in 1 mol L À1 NaOH solution. In 0.5 mol L À1 Na 2 CO 3 /NaHCO 3 solution, the NiFe (OH) x NSs/Ni f electrode exhibits a low OER potential of 290 mV, which is lower than the commercial RuO 2 /Ti electrode at a current density of 100 mA cm À2 , and shows good long-term stability. During electrolysis of Na 2 CO 3 /NaHCO 3 , the cell voltage with the NiFe(OH) x NSs/Ni f anode is 2.52 V, which is 280 mV lower than that with a commercial RuO 2 /Ti anode.[a] Dr.
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