Iron carbide nanoparticles supported on an N-doped carbon porous framework as a bifunctional material for electrocatalytic oxygen reduction and supercapacitors.

Highly active and durable bifunctional materials are of pivotal importance for energy conversion and storage devices, yet a comprehensive understanding of their geometric and electronic influence on electrochemical activity is urgently needed. Fe-N-C materials with physical and chemical structural merits are considered as one of the promising candidates for efficient oxygen reduction reaction electrocatalysts and supercapacitor electrodes. Herein, Fe3C nanoparticles supported on a porous N-doped carbon framework (denoted as Fe3C/PNCF) were readily prepared by one-step chemical vapor deposition under the assistance of a NaCl salt template. The experiment results revealed that the as-synthesized Fe3C/PNCF nanocomposites successfully displayed attractive electrocatalytic oxygen reduction reaction (ORR) activity comparable to that of the Pt/C catalyst (E1/2 of 0.84 V and 0.83 V, respectively), and a superior capacitance of 385.3 F g-1 under 1 A g-1 for a supercapacitor. It's proposed that the increased pyridinic and graphitic N coordination on the hydrophilic porous framework provides more electrochemical active surface area for the storage and transport of electrolyte ions. Additionally, an appropriate d-band center created by the optimized adsorption function endows Fe3C/PNCF with excellent electrochemical properties. The results confirmed that the integration strategy of porous heterogeneous structure and accessible active sites balanced the complex relationship between geometry, electronic structure, and electrochemical activity. Our research provides a facile approach for fabricating multi-functional nanomaterials applicable in both ORR and supercapacitors in the future.

Sequential recovery of copper and nickel from wastewater without net energy input.

A novel bioelectrochemical system (BES) was designed to recover copper and nickel from wastewater sequentially. The BES has two chambers separated by a bipolar membrane and two cathodes. Firstly, the copper ions were reduced on a graphite cathode with electricity output, and then with an additional bias-potential applied, the nickel ions were recovered sequentially on a copper sheet with electricity input. In this design, nickel and copper can be recovered and separated sequentially on two cathodes. By adjusting the molar ratio of copper and nickel ions to 2.99:1 in wastewater, 1.40 mmol Cu²âº could be recovered with 143.78 J electricity outputs, while 50.68 J electricity was input for 0.32 mmol nickel reduction. The total energy output of copper recovery was far more than the electricity input of nickel reduction. The present technology provides a potential method for heavy metal ion separation and recovery.