“…The distribution of nitrogen can be confirmed by the elemental mapping (Fig. 2 e, f) and indicates that nitrogen atoms are successfully doped into the carbon skeleton, which is essential for good ORR activity and wettability [ 32 ]. Fig.…”
• Hierarchical N-doped porous carbons (NPCs) with large surface area and controllable N-doping are synthesized by ball milling, followed by pyrolysis. • As a Zn-air battery cathode, NPCs have comparable discharge performance to precious metal catalysts and more stability. • NPCs also exhibit an excellent specific capacity and cycling stability when used as supercapacitor electrodes. ABSTRACT Nitrogen-doped carbon materials with a large specific surface area, high conductivity, and adjustable microstructures have many prospects for energy-related applications. This is especially true for N-doped nanocarbons used in the electrocatalytic oxygen reduction reaction (ORR) and supercapacitors. Here, we report a low-cost, environmentally friendly, large-scale mechano
“…The distribution of nitrogen can be confirmed by the elemental mapping (Fig. 2 e, f) and indicates that nitrogen atoms are successfully doped into the carbon skeleton, which is essential for good ORR activity and wettability [ 32 ]. Fig.…”
• Hierarchical N-doped porous carbons (NPCs) with large surface area and controllable N-doping are synthesized by ball milling, followed by pyrolysis. • As a Zn-air battery cathode, NPCs have comparable discharge performance to precious metal catalysts and more stability. • NPCs also exhibit an excellent specific capacity and cycling stability when used as supercapacitor electrodes. ABSTRACT Nitrogen-doped carbon materials with a large specific surface area, high conductivity, and adjustable microstructures have many prospects for energy-related applications. This is especially true for N-doped nanocarbons used in the electrocatalytic oxygen reduction reaction (ORR) and supercapacitors. Here, we report a low-cost, environmentally friendly, large-scale mechano
“…As mentioned above, the adsorption capacity of the electrodes and the ion removal efficiency in (M)CDI can be improved by tuning the pore geometry. A high specific electrode surface area is usually preferred to increase ion adsorption; however, it does not necessarily ensure better performance due to the potential for dead-end or poorly interconnected pores [ 406 ]. These unfavorable pore geometries hinder the diffusion of ions inside pores and thus reduce electro-sorption.…”
“…Cheng et al, [ 430 ] recently reviewed various modification strategies including coating, heteroatom doping, and functionalizing the electrode surfaces to improve the specific capacitance, conductivity, and hydrophilicity of the CDI electrode. Several strategies including insertion of multiple wall CNTs [ 431 ], acid treatment [ 46 , 432 ], base treatment [ 433 , 434 ], oxygen plasma treatment [ 435 ], and heteroatom doping [ 427 ] to introduce surface functional groups [ 406 ] are reported to improve the hydrophilicity of the electrodes. Grafting sulfonic and amine functional groups into the electrode materials was reported to increase hydrophilicity as well as the selective adsorption of ions from saline water [ 436 , 437 ].…”
Climate change, population growth, and increased industrial activities are exacerbating freshwater scarcity and leading to increased interest in desalination of saline water. Brackish water is an attractive alternative to freshwater due to its low salinity and widespread availability in many water-scarce areas. However, partial or total desalination of brackish water is essential to reach the water quality requirements for a variety of applications. Selection of appropriate technology requires knowledge and understanding of the operational principles, capabilities, and limitations of the available desalination processes. Proper combination of feedwater technology improves the energy efficiency of desalination. In this article, we focus on pressure-driven and electro-driven membrane desalination processes. We review the principles, as well as challenges and recent improvements for reverse osmosis (RO), nanofiltration (NF), electrodialysis (ED), and membrane capacitive deionization (MCDI). RO is the dominant membrane process for large-scale desalination of brackish water with higher salinity, while ED and MCDI are energy-efficient for lower salinity ranges. Selective removal of multivalent components makes NF an excellent option for water softening. Brackish water desalination with membrane processes faces a series of challenges. Membrane fouling and scaling are the common issues associated with these processes, resulting in a reduction in their water recovery and energy efficiency. To overcome such adverse effects, many efforts have been dedicated toward development of pre-treatment steps, surface modification of membranes, use of anti-scalant, and modification of operational conditions. However, the effectiveness of these approaches depends on the fouling propensity of the feed water. In addition to the fouling and scaling, each process may face other challenges depending on their state of development and maturity. This review provides recent advances in the material, architecture, and operation of these processes that can assist in the selection and design of technologies for particular applications. The active research directions to improve the performance of these processes are also identified. The review shows that technologies that are tunable and particularly efficient for partial desalination such as ED and MCDI are increasingly competitive with traditional RO processes. Development of cost-effective ion exchange membranes with high chemical and mechanical stability can further improve the economy of desalination with electro-membrane processes and advance their future applications.
“…So far, carbon is still the go‐to material for CDI electrode fabrication because it possesses most of the properties mentioned. Activated carbon, [12–14] carbon nanofibers, [15–17] carbon nanotubes, [18–20] carbon aerogels [21–23] and graphene [24–26] are some of the popular types of carbon used in CDI studies. However, carbon still has a couple of limitations such as low wettability, and particle aggregation.…”
Capacitive deionization (CDI) is a potential technology to provide cost efficient desalinated and/or softened water. Several efforts have been invested in the fabrication of CDI electrodes that not only has outstanding performance but also high chance of large scalability. In this personal account, the different techniques in developing carbon‐based materials are presented together with its actual effect on the surface and electrochemical properties of carbon. The categories presented are based on the studies done by the Electrochemical Reaction and Technology Laboratory, the Ertl Center, different research groups in South Korea, and selected papers from the past three years. Our perspective about research gaps and prospects are also included with the aim to increase interest for CDI research.
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