N-containing Functional Groups Research Articles

Hierarchical porous structure formation mechanism in food waste component derived N-doped biochar: Application in VOCs removal

Nitrogen-doped (N-doped) hierarchical porous carbon was widely utilized as an efficient volatile organic compounds (VOCs) adsorbent. In this work, a series of N-doped hierarchical porous carbons were successfully prepared from the direct pyrolysis process of three food waste components. The porous biochar that derived from bone showed a high specific surface area (1405.06 m2/g) and sizable total pore volume (0.97 cm3/g). The developed hierarchical porous structure was fabricated by the combined effect of self-activation (Carbon dioxide (CO2) and water vapor (H2O)) and self-template. The emission characteristics of activation gas analyzed by Thermogravimetric-Fourier transform infrared spectrometer (TG-FTIR) and the transformation of ash composition in the biochar help to illustrate the pore-forming mechanism. Calcium oxide (CaO) and hydroxylapatite were confirmed as the major templates for mesopores, while the decomposition processes of calcium carbonate (CaCO3) and hydroxylapatite provided a large amount of activation gas (CO2 and H2O) to form micropores. The materials also obtained abundant N-containing surface functional groups (up to 7.84 atomic%) from pyrolysis of protein and chitin. Finally, the porous biochar showed excellent performance for VOCs adsorption with a promising uptake of 288 mg/g for toluene and a high adsorption rate of 0.189 min−1. Aplenty of mesopores distributed in the materials effectively improved the mass transfer behaviors, the adsorption rate got a noticeable improvement (from 0.118 min−1 to 0.189 min−1) benefited from mesopores. Reusable potentials of the hierarchical porous carbons were also satisfying. After four thermal regeneration cycles, the materials still occupied 84.8%–87.4% of the original adsorption capacities.

Facile synthesis of nitrogen-rich porous carbon spheres assisted by NaNH2 as a bifunctional activator and nitrogen source for CO2 capture

It is more important for CO2 adsorbents to simultaneously contain large micropore volume and abundant nitrogen species. In the current work, we proposed a facile approach to synthesis millimeter-sized N-doped porous carbon spheres with developed micropores assisted by NaNH2 as a bifunctional activator and nitrogen source under a mild conditions. The obtained porous carbon spheres show the BET surface areas of 592–2513 m2/g and total N contents of 0.28–5.87 wt% respectively. Abundant micropore volume (pore size < 1 nm) and nitrogen species are mainly created at activation temperature less than 550 °C. The O species formed by preoxidation play an important role in the incorporation of N-containing functional groups that enable the enhancement of CO2 adsorption. The optimal sample of ACSO-Na-550 can achieve high CO2 uptake of 5.83 mmol/g at 0 °C and 1 bar. Furthermore, the ACSO-Na-550 exhibits large CO2/N2 selectivity, excellent recyclability, fast CO2 adsorption rate and high dynamic CO2 uptake due to the synergetic effect of its abundant micropore volume (pore size < 1 nm) and nitrogen species. In addition, the NaNH2 activation possesses the outstanding superiority compared with steam and KOH activation under relatively moderate conditions, endowing porous carbon spheres with promising application for CO2 capture.

Chelating effect between uranyl and pyridine N containing covalent organic frameworks: A combined experimental and DFT approach

Covalent organic frameworks (COFs) are promising adsorbents for removing heavy metal ions, and have high crystallinity, a porous structure, and conjugated stability. N-containing functional groups are known to have great affinity for uranyl ions. In this work, to explore the peculiarity of the pyridine N structure as an efficient adsorbent, we chose 2,2′-dipyridine-5,5′-diamine (Bpy) and pyridine-2,5′-diamine (Py) as the core skeletons, and 1,3,5-triformylphloroglucinol (Tp) as the linker to synthesize two crystalline and stable N-containing COFs named TpBpy and TpPy, respectively, through a facile solvothermal method. Characterization results demonstrated that TpBpy and TpPy possessed regularly growing pore sizes, large specific surface areas and relatively strong thermal resistances. The results of batch experiments showed that both COF materials were capable of the effective removal of uranyl with uptake capacities of 115.45 mg g−1 and 291.79 mg g−1, respectively. In addition, density functional theory (DFT) simulations highlighted the beneficial chelation effect of the double N structure in pyridine monomers for removing uranyl ions. Combining systematic experimental and theoretical analyses, the adsorption process and interaction mode of porous COFs and UO22+ were revealed, to provide predictable support for the application of pyridine N-containing COFs in the field of environmental remediation.

Carbon Dioxide Adsorption on Carbon Nanofibers with Different Porous Structures

Electrospinning techniques have become an efficient way to produce continuous and porous carbon nanofibers. In view of CO2 capture as one of the important works for alleviating global warming, this study intended to synthesize polyacrylonitrile (PAN)-based activated carbon nanofibers (ACNFs) using electrospinning processes for CO2 capture. Different structures of PAN-based ACNFs were prepared, including solid, hollow, and porous nanofibers, where poly(methyl methacrylate) (PMMA) was selected as the sacrificing core or pore generator. The results showed that the PMMA could be removed successfully at a carbonization temperature of 900 °C, forming the hollow or porous ACNFs. The diameters of the ACNFs ranged from 500 to 900 nm, and the shell thickness of the hollow ACNFs was approximately 70–110 nm. The solid ACNFs and hollow ACNFs were microporous materials, while the porous ACNFs were characterized by hierarchical pore structures. The hollow ACNFs and porous ACNFs possessed higher specific surface areas than that of the solid ACNFs, while the solid ACNFs exhibited the highest microporosity (94%). The CO2 adsorption capacity on the ACNFs was highly dependent on the ratio of V&lt;0.7 nm to Vt, the ratio of Vmi to Vt, and the N-containing functional groups. The CO2 adsorption breakthrough curves could be curve-fitted well with the Yoon and Nelson model. Furthermore, the 10 cyclic tests demonstrated that the ACNFs are promising adsorbents.

Green synthesis of a novel functionalized chitosan adsorbent for Cu(II) adsorption from aqueous solution.

Pollution generated by heavy metals has become a global environmental issue with much public concern. Herein, a functionalized chitosan-based adsorbent (CS-PAR) was synthesized via a simple one-step method for the adsorption of copper ions in solutions. A series of characterization methods have shown that CS-PAR was successfully synthesized. The experimental results showed that the maximum adsorption capacity of CS-PAR for Cu(II) ions was 170.23 mg/g. The adsorption process of Cu(II) on CS-PAR conformed to Langmuir and pseudo second-order models and belonged to a single-layer chemical adsorption process on the surface of a homogeneous medium. The adsorption mechanism of the adsorbent to Cu(II) ions was the complexation between the N-containing functional groups existing on the surface of the adsorbent and Cu(II). These results also showed that the adsorbent was an efficient material for removing heavy metal copper in wastewater and had very important practical significance.

Insight into the KOH/KMnO4 activation mechanism of oxygen-enriched hierarchical porous biochar derived from biomass waste by in-situ pyrolysis for methylene blue enhanced adsorption

A high-performance hierarchical porous carbon enriched in oxygen-containing functional groups was prepared by using pine as the raw material, KOH and KMnO4 as a green activator via cost-effective one-step or two-step in-situ pyrolysis processes. The adsorption performance, kinetics and thermodynamics of activated biochar were evaluated using methylene blue (MB) as a model pollutant. Biochar structure was investigated by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), N2 adsorption/desorption isotherms (BET) and scanning electron microscopy (SEM) to explore its morphological, physical, and chemical properties. A possible adsorption mechanism and pathway were also proposed. The results showed that a two-step process, higher activation (KOH and KMnO4) to biomass ratio led to excellent adsorption performance. AC-KOH-1-1 and AC-KMnO4-1-3 presented the maximum equilibrium adsorption capacities of 637.5 mg/g and 439.5 mg/g, respectively. The adsorption isotherm fit well with the Freundlich isotherm model and pseudo-second-order kinetic model, which exhibited better monolayer adsorption and chemical adsorption control. In addition, the adsorption was dominated by pore diffusion and π-π stacking interactions for KOH activation due to the well-developed pore volume (0.04990 mg/L), pore channel (18.65 nm), aromatized structure (66.03 %) and surface defective structure. However, the adsorption capacity was controlled by hydrogen bonding, electrostatic adsorption interactions, cation exchange and the donor-receptor-effect for AC-KMnO4 due to it having the highest proportion of O- and N-containing functional groups. Therefore, this cost-efficient biochar preparation technology for the efficient removal of organic pollutants has great potential for practical application.

Natural Honeycomb-like structure cork carbon with hierarchical Micro-Mesopores and N-containing functional groups for VOCs adsorption

It can be said that most of the garbage were misplaced resources. And how to turn these resources into valuable products is extremely important. In this study, the cork wine stoppers were recovered and prepared into VOCs adsorption materials through ammonia activation. The prepared cork biomass carbon had abundant micropores and mesopores and rich N-containing functional groups, especially amino groups (3.6%). The obtained sample NC900 exhibited a good performance for the adsorption of acetone (1221 mg g−1 at 18 kPa), benzene (840 mg g−1 at 10 kPa) and toluene (720 mg g−1 at 3 kPa) at 25 °C. The adsorption effect of hierarchical porous carbon on VOCs under different pressures were calculated and analyzed through GCMC. Multilayer adsorption promoted the adsorption of VOCs molecules in mesopores under the high pressure. The promotion effects of nitrogen-containing functional groups (amino, pyrrolic, pyridine) based on adsorption energy calculations were evaluated via DFT. The amino functional groups obtained the strongest affinity for acetone (-0.64 eV), benzene (-0.66 eV) and toluene (-0.72 eV). This study achieved a guiding significance for the preparation of cork biomass carbon and its application in the VOCs adsorption.

Nano-channel-based physical and chemical synergic regulation for dendrite-free lithium plating

Uncontrollable dendrite growth resulting from the non-uniform lithium ion (Li+) flux and volume expansion in lithium metal (Li) negative electrode leads to rapid performance degradation and serious safety problems of lithium metal batteries. Although N-containing functional groups in carbon materials are reported to be effective to homogenize the Li+ flux, the effective interaction distance between lithium ions and N-containing groups should be relatively small (down to nanometer scale) according to the Debye length law. Thus, it is necessary to carefully design the microstructure of N-containing carbon materials to make the most of their roles in regulating the Li+ flux. In this work, porous carbon nitride microspheres (PCNMs) with abundant nanopores have been synthesized and utilized to fabricate a uniform lithiophilic coating layer having hybrid pores of both the nano- and micrometer scales on the Cu/Li foil. Physically, the three-dimensional (3D) porous framework is favorable for absorbing volume changes and guiding Li growth. Chemically, this coating layer can render a suitable interaction distance to effectively homogenize the Li+ flux and contribute to establishing a robust and stable solid electrolyte interphase (SEI) layer with Li-F, Li-N, and Li-O-rich contents based on the Debye length law. Such a physical-chemical synergic regulation strategy using PCNMs can lead to dendrite-free Li plating, resulting in a low nucleation overpotential and stable Li plating/stripping cycling performance in both the Li‖Cu and the Li‖Li symmetric cells. Meanwhile, a full cell using the PCNM coated Li foil negative electrode and a LiFePO4 positive electrode has delivered a high capacity retention of ∼ 80% after more than 200 cycles at 1 C and achieved a remarkable rate capability. The pouch cell fabricated by pairing the PCNM coated Li foil negative electrode with a NCM 811 positive electrode has retained ∼ 73% of the initial capacity after 150 cycles at 0.2 C.

Characteristics of Graphite Felt Electrodes Treated by Atmospheric Pressure Plasma Jets for an All-Vanadium Redox Flow Battery.

In an all-vanadium redox flow battery (VRFB), redox reaction occurs on the fiber surface of the graphite felts. Therefore, the VRFB performance highly depends on the characteristics of the graphite felts. Although atmospheric pressure plasma jets (APPJs) have been applied for surface modification of graphite felt electrode in VRFBs for the enhancement of electrochemical reactivity, the influence of APPJ plasma reactivity and working temperature (by changing the flow rate) on the VRFB performance is still unknown. In this work, the performance of the graphite felts with different APPJ plasma reactivity and working temperatures, changed by varying the flow rates (the conditions are denoted as APPJ temperatures hereafter), was analyzed and compared with those treated with sulfuric acid. X-ray photoelectron spectroscopy (XPS) indicated that the APPJ treatment led to an increase in O-/N-containing functional groups on the GF surface to ~21.0% as compared to ~15.0% for untreated GF and 18.0% for H2SO4-treated GF. Scanning electron microscopy (SEM) indicated that the surface morphology of graphite felt electrodes was still smooth, and no visible changes were detected after oxidation in the sulfuric acid or after APPJ treatment. The polarization measurements indicated that the APPJ treatment increased the limiting current densities from 0.56 A·cm−2 for the GFs treated by H2SO4 to 0.64, 0.68, and 0.64 A·cm−2, respectively, for the GFs APPJ-treated at 450, 550, and 650 °C, as well as reduced the activation overpotential when compared with the H2SO4-treated electrode. The electrochemical charge/discharge measurements showed that the APPJ treatment temperature of 550 °C gave the highest energy efficiency of 83.5% as compared to 72.0% with the H2SO4 treatment.

Atomically Dispersed Manganese Lewis Acid Sites Catalyze Electrohydrogenation of Nitrogen to Ammonia

Atomically Dispersed Manganese Lewis Acid Sites Catalyze Electrohydrogenation of Nitrogen to Ammonia

Cellulose acetate-polyurethane film adsorbent with analyte enrichment for in-situ detection and analysis of aqueous Pb using Laser-Induced Breakdown Spectroscopy (LIBS)

In this work, we have investigated the potential application of cellulose acetate-polyurethane (CA-PU) film, as an adsorbent material as well as an enrichment medium for aqueous Pb quantification using Laser-Induced Breakdown Spectroscopy (LIBS). CA-PU was reported to be a good adsorbent for Pb removal from water medium due to its possession of O- and N-containing functional groups. The adsorption was first qualitatively investigated by observing Pb I (405.7 nm) emission line, before and after the adsorption. The study was further carried out using varied laser energies in order to optimize the produced spectra. The optimum laser energy was 54 mJ (gain = 1,500; width = 30 µs). The other aspects this work considered were contact time and pH, where the stable analysis was obtained after 12 h enrichment process and at pH 7. Normalization using C I (247.8 nm) internal standard line could compensate for the errors generated during the analysis. The non-linear regression of the calibration curve achieved correlation as high as R2 = 0.99997 and LOD = 1.02 mg/L. Based on the obtained LOD, this analytical method is suitable for the wastewater control in chemical industries in Indonesia. As an addition, LIBS is a potential technique to measure the binding energy of the adsorbent surface which requires further studies.

KOH modification effectively enhances the Cd and Pb adsorption performance of N-enriched biochar derived from waste chicken feathers.

Waste chicken feathers are the ideal precursor for the production of low-cost N-enriched biochar. KOH-modified N-enriched biochar (KNB) containing 15.92wt% N was successfully prepared using waste chicken feathers. The adsorption kinetics results showed that KNB had rapid Cd (2h) and Pb (1h) adsorption rates. The Cd and Pb adsorption capacities of KNB (the values of KF were 22.324 (Cd) and 119.654 (Pb) mg1-(1/n)·L1/n·g-1) were 7.07 and 26.52 times higher than those of the original biochar based on the adsorption isotherm results. The KNB was stable at pH 3-6 and had stronger co-adsorption capacities in double-ion systems. Based on the adsorption experiments and various characterization methods, we concluded that the primary Cd and Pb adsorption mechanisms of KNB involved electrostatic interactions, cation-π interactions, complexation, and K+ exchange. The precipitation mechanism could partially account for Pb adsorption but not for Cd adsorption. KOH modification enhanced the electronegativity of biochar and then increased the electrostatic attraction. Surface O- and N-containing functional groups were involved in Cd and Pb adsorption. Graphitic-N, oxidised-N, and OCO were the main active adsorption groups, the relative contents of which increased after KOH modification, thus increasing the Cd and Pb adsorption performance. Therefore, KNB can be used as a fast and highly efficient adsorption agent to remove Cd and Pb from wastewater containing either Cd and Pb or a combination of these two metals.

A regenerable N-rich hierarchical porous carbon synthesized from waste biomass for H2S removal at room temperature

In this study, N-rich hierarchical porous carbons (NPCs) were synthesized via one step strategy from cypress sawdust with carbon nitride (CN) loading and K2CO3 activation. NPCs exhibited excellent performance for H2S removal with the sulfur capacity up to 426.2 mg/g at room temperature. It was much higher than 12.5 mg/g of porous carbon (PC) which was only activated by K2CO3. The NPCs with CN loading showed hierarchical porous structure with micropores and mesopores volume up to 0.434 and 0.597 cm3/g, respectively. Moreover, NPCs had high N contents (up to 12.37 wt%) and high relative contents of pyridinic N and pyrrolic N within 76.61–84.37%, which were identified as active sites for H2S adsorption by density functional theory calculation, enhancing H2S removal. The formation mechanism of NPCs was investigated by TG-FTIR, suggesting that CN pyrolysis result in hierarchical porous structure and rich N-containing functional groups by gradually releasing H2O, CO2 and NH3. Moreover, the NPCs showed high regeneration ability, remaining 86.6% of the initial sulfur capacity after five regeneration cycles, and sulfur (S) was the main desulfurization product (H2S + O2 → S + H2O). The results demonstrate that NPCs are promising catalysts to remove H2S efficiently with low cost and high reusability.

Simultaneous electrochemical sensing of heavy metal ions based on a g-C3N4/CNT/NH2-MIL-88(Fe) nanocomposite.

The presence of Cd2+, Pb2+, Cu2+ and Hg2+ in drinking-water can be harmful to human health, even if their concentration is fairly low. Hence, it is significant to detect these heavy metal ions in sewage to evaluate the quality of water. Herein, amino-functionalized metal-organic frameworks (NH2-MIL-88(Fe)) embedded with graphitic carbon nitride (g-C3N4) nanosheets and acid-functionalized carbon nanotubes were prepared via a one-pot synthesis. The composite can be directly modified on the surface of glass carbon electrodes without the assistance of Nafion or other binders. The modified glass carbon electrodes can be used to simultaneously detect Cd2+, Pb2+, Cu2+ and Hg2+ in water via square wave stripping voltammetry. The doping of g-C3N4 in the composite, rich in N-containing functional groups, participates in the adsorption of metal ions on the surface of the electrodes. The porous composite provides accommodation room for metals generated by electro-reduction. The detection limit for Cd2+, Pb2+, Cu2+ and Hg2+ is 39.6 nM, 7.6 nM, 11.9 nM, and 9.6 nM, respectively. And the sensitivity for Cd2+, Pb2+, Cu2+ and Hg2+ is 0.0789 mA μM-1 cm-2, 0.4122 mA μM-1 cm-2, 0.2616 mA μM-1 cm-2, and 0.3251 mA μM-1 cm-2, respectively. This work not only enriches the functional design of Fe-MOF materials, but also develops a method for the determination of metal ions using the adsorption sites in g-C3N4.

Adsorption-enrichment characterization of CO2 and dynamic retention of free NH3 in functionalized biochar with H2O/NH3·H2O activation for promotion of new ammonia-based carbon capture

CO2 emission reduction has become a global consensus, and the most potential carbon emission reduction technology-Carbon Capture and Storage (CCS) is still in the development stage. In order to make up for the shortcomings of CCS technology, the idea of functionalized biochar-ammonia carbon capture system is proposed. Corn straw was used as raw materials, and activated biochar were prepared by one-step/two-step H2O/NH3·H2O activation, to construct a hierarchical-functionalized structure of biochar, and explore its adsorption characteristics of CO2 and NH3. Various methods such as solid characterization, temperature programmed desorption, molecular dynamics and quantum chemical simulation were used to explore the structure-effect relationship between the physicochemical properties of biochar and the adsorption of CO2 and NH3. The results show that the pore structure of gas-physical activated biochar is dominated by micropores. The one-step method is beneficial to the construction of functional groups on biochar surface, while the two-step one is conducive to the improvement of pore formation and its aromatization. During NH3·H2O activation, NH3 would inhibit the formation of O-containing functional groups on the surface of biochar by H2O. Compared with O-containing groups, the N-containing functional groups on biochar surface have greater adsorption energy for CO2 and NH3 adsorption. The adsorption sites of CO2 and NH3 are mainly in the micropores (d < 0.7 nm), and the contribution of functional groups in the micropores to the adsorption of CO2 and NH3 is greater than the pore structure. This study provided theoretical basis for the development of new biochar-ammonia CO2 capture system.

One-step synthesis of microporous nitrogen-doped biochar for efficient removal of CO2 and H2S

It is still a great challenge to prepare an ideal adsorbent for the removal of CO2 and H2S from biogas efficiently. In this study, urea phosphate (UP) was selected as both activator and nitrogen (N) source to prepare the biochar adsorbent from plant biomass with microporous structure and N-rich functional groups through “one-step” synthesis. The results show that the yield of biochar increased from about 20% to 50%, and the SBET and Vmic of the obtained biochar were 1189 m2/g and 0.433 cm3/g, respectively, which was much higher than those without UP addition (524 m2/g and 0.17 cm3/g). Moreover, N was successfully doped on the surface of biochar, and the N content was up to 4.24 at.% with the majority of basic species such as pyridinic and pyrrolic N. This could be attributed to a large amount of N-containing functional groups and phosphoric acid released gradually at the presence of UP during the heating process. The prepared biochar exhibited good CO2 and H2S adsorption capacities up to 1.34 mmol/g and 54.8 mg/g, respectively, which was much higher than those without UP addition (0.958 mmol/g and 0.24 mg/g). The excellent adsorption properties of CO2 and H2S were tightly related to the improved microporous structure and surface basic N-containing functional groups on the biochar.

Electron-transfer-dominated non-radical activation of peroxydisulfate for efficient removal of chlorophenol contaminants by one-pot synthesized nitrogen and sulfur codoped mesoporous carbon

Synergistic adsorption and oxidative degradation (via persulfate activation) on metal-free carbonaceous materials are expected to be environmentally friendly and highly efficient approach toward contaminants removal. Herein, nitrogen and sulfur codoped mesoporous carbon (NSDMC) were firstly synthesized via co-carbonization of calcium citrate and thiourea without any templates. NSDMC samples exhibit remarkably enhanced adsorption capacity and oxidative degradation (by activating PDS) for chlorophenols elimination. Increased SBET and introduced N-containing functional groups are beneficial for chlorophenols adsorption, PDS accessibility and successive activation. Doped sulfur species (especially for thiophenic S) can enhance the electron-transport performance of NSDMC, further promoting PDS activation and chlorophenols degradation. It can be ascribed to the synergistic effect of N and S codoping. NSDMC-30 (containing 5.83 at.% nitrogen and 2.15 at.% sulfur, and possessing SBET of 1935.9 m2 g−1) exhibits the optimal adsorption and catalytic oxidation capability for 4-CP removal. Degradation rate constant of NSDMC-30 is 0.125 min−1, which is 3.0 times and 7.8 times higher than nitrogen-doped MC and pristine MC, respectively. Radicals quenching experiments and EPR tests demonstrate that non-radical pathways play dominant role for PDS activation and chlorophenols degradation. Based on the influences of catalyst loading, initial 4-CP concentration, and PDS dosage on degradation kinetics of 4-CP, the pre-adsorption is unveiled to be the critical step determining oxidation rate of chlorophenols. More importantly, the results of in-situ Raman and electrochemical tests show that the surface-confined and activated PDS complex (carbon-PDS*) and continuous electron transfer from co-adsorbed 4-CP are mainly responsible for the oxidative degradation of chlorophenols. The intermediate products and TOC removal indicate that chlorophenols can be efficiently degraded and mineralized by as-synthesized NSDMC via activating PDS. Besides, the present NSDMC/PDS system is also applicable for purification of actual polluted water samples. This work provides in-depth knowledge of carbon-driven nonradical process for PDS activation and contaminants remediation.

Functionalized construction of biochar with hierarchical pore structures and surface O-/N-containing groups for phenol adsorption

Volatile organic compounds (VOCs) seriously endanger human health due to their bioaccumulation and carcinogenic effects, while biochar adsorption method is regarded as one of the most potential VOCs removal technologies. In order to clarify the structure-activity relationship of biochar adsorption of VOCs, corn straw was used as a biomass raw material for chemically activated biochar preparation and liquid-phase adsorption experiments. The simulations including molecular dynamics simulations and quantum chemical simulations were carried out to verify the relevant conclusions. The results show that abundant O-/N-containing functional groups are constructed on the pore surface of chemically activated biochar, forming a typical hierarchical-functionalized pore structure. The hierarchical-functionalized pore structure has an ideal promotion effect on the adsorption of phenol. Specifically, mesoporous structure on biochar surface mainly determines adsorption of phenol. The hydroxyl group strengthens the adsorption of phenol, due to the increased electrostatic effect, while N-6 enhances the van der Waals force for the change of adsorption site, thereby strengthening the adsorption of phenol. This work provides theoretical support for the practical application of biochar for efficient VOCs removal technology.

Anion-Modulated Platinum for High-Performance Multifunctional Electrocatalysis toward HER, HOR, and ORR.

SummaryEfficient electrocatalyst toward hydrogen evolution/oxidation reactions (HER/HOR) and oxygen reduction reaction (ORR) is desirable for water splitting, fuel cells, etc. Herein, we report an advanced platinum phosphide (PtP2) material with only 3.5 wt % Pt loading embedded in phosphorus and nitrogen dual-doped carbon (PNC) layer (PtP2@PNC). The obtained catalyst exhibits robust HER, HOR, and ORR performance. For the HER, a much low overpotential of 8 mV is required to achieve the current density of 10 mA cm−2 compared with Pt/C (22 mV). For the HOR, its mass activity (MA) at an overpotential of 40 mV is 2.3-fold over that of the Pt/C catalyst. Interestingly, PtP2@PNC also shows exceptional ORR MA which is 2.6 times higher than that of Pt/C and has robust stability in alkaline solutions. Undoubtedly, this work reveals that PtP2@PNC can be employed as nanocatalysts with an impressive catalytic activity and stability for broad applications in electrocatalysis.

Al homogeneous deposition induced by N-containing functional groups for enhanced cycling stability of Al-ion battery negative electrode

Rechargeable Al-ion batteries (AIBs) are considered as one of the most fascinating energy storage systems due to abundant Al resource and low cost. However, the cycling stability is subjected to critical problems for using Al foil as negative electrode, including Al dendrites, corrosion and pulverization. For addressing these problems, here a lightweight self-supporting N-doped carbon rod array (NCRA) is demonstrated for a long-life negative electrode in AIBs. Experimental analysis and first-principle calculations reveal the storage mechanism involving the induced deposition of N-containing function groups to Al as well as the ideal skeleton of the NCRA matrix for Al plating/stripping, which is favorable for regulating Al nucleation and suppressing dendrites growth. Compared with the Al foil, the NCRA exhibits lower areal mass density (∼ 72% of Al foil), smaller thickness (40% of Al foil), but much longer cycle life (> 4 times of Al foil). Benefiting from the remarkable stability of the array structure, symmetric cells show excellent cycling stability with small voltage hysteresis (∼ 80 mV) and meanwhile there are no corrosion and pulverization problems even after cycled for 120 hours. Besides, full cells also manifest long lifespan (1,500 cycles) and increased Coulombic efficiency (100±1%).