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This review focuses on the recovery of REEs from waste with ionic liquids (ILs) as dilutants and extractants to tackle the REE supply challenge.

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.

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