Mesopore dominated capacitive deionization of N-doped hierarchically porous carbon for water purification

A review of hierarchical porous carbon derived from various 3D printing techniques

Hierarchical porous carbon is an area of advanced materials that plays a pivotal role in meeting the increasing demands across various industry sectors including catalysis, adsorption, and energy storage and conversion. Additive manufacturing is a promising technique to synthesize architectured porous carbon with exceptional design flexibility, guided by computer-aided precision. This review paper aims to provide an overview of porous carbon derived from various additive manufacturing techniques, including material extrusion, vat polymerization, and powder bed fusion. The respective advantages and limitations of these techniques will be examined. Some exemplary work on various applications will be showcased. Furthermore, perspectives on future research directions, opportunities, and challenges of additive manufacturing for porous carbon will also be offered.

Ethylenediamine modulate bonding interaction of solvation structure for wide-temperature aqueous ammonium-ion capacitor

Aqueous ammonium-ion capacitors (AAICs) are promising for large-scale energy storage owing to low cost and inherent safety, while their practical applications are suffered from performance under extreme environment. Low ion conductivity and high viscosity, as well as freezing of the electrolyte, are the main issues for the electrochemical performance failure at low temperatures. In this work, the AAICs were assembled with commercial carbon electrodes and antifreeze electrolyte, where the electrolyte with a freezing point lower than -115 °C is developed by using Ethylenediamine (EDA) as an additive with a volume ratio of 50 % to an aqueous solution of 0.5 M NH4Cl. This antifreeze electrolyte displays a superior ionic conductivity of 8.58 mS cm-1 and a weaker viscosity of 8.16 mPa s at low temperatures. Furthermore, the spectroscopic investigations and molecular dynamics (MD) simulations demonstrate that the addition of EDA can break the hydrogen bonds of water molecules and modulate the solvation structure. Therefore, the assembled AAICs with electrolytes of 0.5 M NH4Cl (50 %-EDA) could be operated at wide-temperature conditions steadily, exhibiting excellent capacity, rate performance and good cycling stability. This work provides a simple and effective strategy for wide-temperature energy storage devices.

1D hollow tubular/2D nanosheet hybrid dimensional porous carbon prepared by one-step carbonization using natural minerals as templates for supercapacitors

The reasonable construction of one-dimensional (1D)/two-dimensional (2D) hybrid dimensional porous carbon materials with complementary advantages and disadvantages is an important approach to addressing the structural and performance deficiencies of single carbon materials, while also significantly improving the electrochemical performance of super-capacitors. In this study, 1D hollow tubular/2D nanosheet hybrid dimensional porous carbon was synthesized through one-step carbonization using 1D fibrous brucite and 2D layered magnesium carbonate hydroxide as templates. By adjusting the feed ratio of 1D fibrous and 2D layered templates, the morphology, pore structure and specific surface area (SSA) of the prepared 1D hollow tubular/2D nanosheet hybrid dimensional porous carbon were controlled. The prepared hybrid dimensional porous carbons were characterized using scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption-desorption. And their electrochemical performance was also studied by cyclic voltammograms (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). The results show that the use of templates with different dimensions significantly influences the morphology, pore structure, SSA and electrochemical performance of the synthesized hybrid dimensional porous carbon. The hybrid dimensional porous carbon (3F) exhibits a high specific capacitance and excellent cycling stability. 3F demonstrates the specific capacitance of 245.3 F g-1 at 1 A g-1. Furthermore, the capacity retention rate remains as high as 93.4% after 8000 cycles at 10 A g-1. This work reveals that hybrid dimensional porous carbon composed of 1D hollow carbon tubes and 2D carbon nanosheets has great potential for use in supercapacitor electrode materials.

Tailoring B, N-Enriched Carbon Nanosheets via a Gelation-Assisted Strategy for High-Capacity and Fast-Response Capacitive Desalination

Designing high-performance carbonous electrodes for capacitive deionization with remarkable salt adsorption capacity (SAC) and outstanding salt adsorption rate (SAR) is quite significant yet challenging for brackish water desalination. Herein, a unique gelation-assisted strategy is proposed to tailor two-dimensional B and N-enriched carbon nanosheets (BNCTs) for efficient desalination. During the synthesis process, boric acid and polyvinyl alcohol were cross-linked to form a gelation template for the carbon precursor (polyethyleneimine), which endows BNCTs with ultrathin thickness (∼2 nm) and ultrahigh heteroatoms doping level (14.5 atom % of B and 14.8 atom % of N) after freeze-drying and pyrolysis. The laminar B, N-doped carbon enables an excellent SAC of 42.5 mg g-1 and fast SAR of 4.25 mg g-1 min-1 in 500 mg L-1 NaCl solution, both of which are four times as much as those of activated carbon. Moreover, the density functional theory (DFT) calculation demonstrates that the dual doping of B and N atoms firmly enhances the adsorption capacity of Na+, leading to a prominent chemical SAC for brackish water. This work paves a new way to rationally integrate both conducive surface morphology and systematic effects of B, N doping to construct high-efficiency carbonaceous electrodes for desalination.

Electrode Materials for Desalination of Water via Capacitive Deionization

Recent years have seen the emergence of capacitive deionization (CDI) as a promising desalination technique for converting sea and wastewater into potable water, due to its energy efficiency and eco-friendly nature. However, its low salt removal capacity and parasitic reactions have limited its effectiveness. As a result, the development of porous carbon nanomaterials as electrode materials have been explored, while taking into account of material characteristics such as morphology, wettability, high conductivity, chemical robustness, cyclic stability, specific surface area, and ease of production. To tackle the parasitic reaction issue, membrane capacitive deionization (mCDI) was proposed which utilizes ion-exchange membranes coupled to the electrode. Fabrication techniques along with the experimental parameters used to evaluate the desalination performance of different materials are discussed in this review to provide an overview of improvements made for CDI and mCDI desalination purposes.

Electro-adsorption of Cs(I) ions from aqueous solution by capacitive deionization using ACC/MoO3 composite electrode

The separation of Cs⁺ from radioactive wastes is of paramount importance, but still a challenge. In this paper, ACC/MoO₃ composite electrode was prepared and used for the separation of Cs⁺ by capacitive deionization (CDI). The electrode materials were characterized by SEM-EDS, FTIR, XPS before and after adsorption experiments. The composite electrode was composed of ACC and hexagonal tunnel structure of MoO₃, which had a mesoporous structure. The specific surface area, average pore diameter, total pore volume and maximal specific capacitance were 170.4 m² g^-1, 2.127 nm, 0.906 cm³ g^-1 and 76.3 F g^-1, respectively. The adsorption kinetics, isotherms, and the mass transfer process were analyzed, and the possible adsorption mechanism was proposed. The removal efficiency of Cs⁺ increased with the increase of voltage and the decrease of Cs⁺ concentration, which reached 44.7 % after 240 min when voltage was 1.2 V and Cs⁺ concentration was 5 mg L^-1. The Cs⁺ adsorption onto the ACC/MoO₃ composite was multi-layer adsorption and the adsorption to active sites (AAS) was the rate-limiting step. Overall, the ACC/MoO₃ composite was a potential electrode for Cs⁺ separation.