Effects of Intrinsic Pentagon Defects on Electrochemical Reactivity of Carbon Nanomaterials

Interfacial Electronic Structure Modulation of Hierarchical Co(OH)F/CuCo2S4 Nanocatalyst for Enhanced Electrocatalysis and Zn-Air Batteries Performances

The exploration of robust multifunctional electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a continuing challenge for the sustainable energy sources. However, as the key reactions in renewable metal-air batteries and fuel cells, the energy conversion efficiencies of ORR and OER are greatly affected by their reaction kinetics. In addition to designing excellent electrocatalysts, new methods to stabilize the electrolyte/electrode interfaces are urgently needed. Herein, a hierarchical Co(OH)F/CuCo₂S₄ hybrid was created as an efficient catalyst for OER and ORR in alkaline media. Combining spinel ferrite with the hydroxide can greatly boost their catalytic performance. The optimal Co(OH)F/CuCo₂S₄ hybrid exhibits superior OER performance and durable stability, as demonstrated by an ultralow overpotential of 230 mV at 10 mA·cm^-2. The onset potential and the half-wave potential in 0.1 M KOH solution for ORR are 0.88 and 0.80 V, respectively. Furthermore, the Co(OH)F/CuCo₂S₄ hybrid served as a catalyst in Zn air batteries catalyst exhibits a low overpotential of 1.12 V at 50.0 mA·cm^-2, large power density of 144 mW·cm^-2, and a long electrochemical lifetime of 118 h (118 cycles), which is even better than those of the Pt/C and RuO₂ catalysts. The rational integration of spinel and hydroxide at the interface can provide multifunctional electrocatalysis and possess a high reactivity for oxygen conversion. Synergistic coupling effect and interfacial electronic interaction between Co(OH)F and CuCo₂S₄ can significantly enhance the electron transfer rate, and these synergistic advantages enable the heterogeneous structure of the multifunctional electrocatalyst to produce excellent catalytic performance.

Large-scale fabrication of N-doped porous carbon nanosheets for dye adsorption and supercapacitor applications

The development of novel large-scale synthesis protocols for heteroatom-doped porous carbon nanosheets is highly imperative for wastewater purification and high-performance electrode materials. In the present work, we propose a simple and feasible explosion-assisted activation strategy to fabricate a kind of N-doped porous carbon nanosheet (N-PCNS) at a large scale, in which only lactose and zinc nitrate were used as raw materials. The obtained N-PCNS possesses hierarchical micro- and mesopore nanostructures with a high specific surface area of 879 m2 g-1 while keeping a high nitrogen content of 3.73 at%. The adsorption properties of the N-PCNS were systematically evaluated through adsorption of neutral red (NR) dye. The adsorption capacity of the N-PCNS was as high as 439.6 mg g-1, meanwhile the adsorption process exhibited fine correlation with the Langmuir isotherm and pseudo-second-order kinetic models. As an electrode material for supercapacitors, the specific capacitance of the N-PCNS is up to 263 F g-1 at 1 A g-1 and 194 F g-1 at 20 A g-1, revealing superior rate performance. The capacitance retention after 10 000 cycles at 20 A g-1 is 96%, demonstrating excellent cycling stability. Our work provides an effective approach to achieve the large-scale preparation of high-performance doped carbon materials.

Sandwich-like NiCo layered double hydroxide/reduced graphene oxide nanocomposite cathodes for high energy density asymmetric supercapacitors

Lab-synthesized sandwich-like LDH/rGO composites were assembled into asymmetric supercapacitors exhibiting high energy density and excellent cycling stability.