Unlocking the critical roles of N, P Co-Doping in MXene for Lithium-Oxygen Batteries: Elevated d-Band center and expanded interlayer spacing.

The design and fabrication of bifunctional catalysts with high electrocatalytic activity and stability are critical for developing highly reversible Li-O2 batteries (LOBs). Herein, the N, P co-doped MXene (NP-MXene) is prepared by one-step annealing method and evaluated as bifunctional catalyst for LOBs. The results suggest that the P doping plays a crucial role in increasing interlayer distance of MXene, thereby effectively providing more active sites, fast mass transfer, and ample space for the deposition/decomposition of Li2O2. Moreover, the N doping can significantly elevate the d-band center of Ti, thereby remarkably improving the adsorption of reaction intermediates and accelerating the deposition/decomposition of Li2O2 films. Consequently, the MXene-based LOBs deliver an ultrahigh specific capacity of 13,995 mAh/g at 500 mA g-1, a discharge/charge voltage gap of 0.89 V, and a cycle life up to 523 cycles with a limited capacity of 1000 mAh/g at 500 mA g-1. Impressively, the as-fabricated flexible LOBs with NP-MXene cathode display excellent cycling stability and ability to continuously power LEDs even after bending. Our findings pave the road of heteroatom doped MXenes as next-generation electrodes for high-performance energy storage and conversion systems.

N/P co-doped MXene hollow microcapsules by surfactants assisted hydrothermal-freeze drying for adjustable permeability.

The assembly of MXene materials into microcapsules has drawn great attentions due to their unique properties. However, rational design and synthesis of MXene-based microcapsules with specific nanostructures at the molecular scale remains challenging. Herein, we report a strategy to synthesize N/P co-doped MXene hollow flower-like microcapsules with adjustable permeability via dual surfactants assisted hydrothermal-freeze drying method. In contrast to anionic surfactants, cationic surfactants exhibited effective electrostatic interactions with MXene nanosheets during the hydrothermal process. Manipulation of dual surfactants in hydrothermal process realized N and P co-doping of MXene to improve flexibility and promoted the generation of abundant internal cavities in flower-like microcapsules. Based on the unique microstructure, the prepared hollow flower-like microcapsules showed excellent performance, stability and reusability in size-selective release of small organic molecules. Moreover, the release rate can be controlled by turning the oxidation state and type of MXene. The strategy delineates promising prospects for the design of MXene-based microcapsules with specific structures.

[Preparation of Bamboo-based N, P Co-doped Activated Carbon and Its Lanthanum Ion Adsorption Performance].

Using diammonium hydrogen phosphate as an activator and N and P source and and bamboo chips as the carbon source, N, P co-doped activated carbon was prepared by one-step pyrolysis and used to efficiently remove La3+ in aqueous solutions. The effects of activation temperature and pH value on the adsorption performance of La3+ were analyzed, and the activation and adsorption mechanisms were explored using TG-IR, SEM-EDX, pore structure, XPS, and hydrophilicity. The results showed that diammonium hydrogen phosphate easily decomposed at a high temperature to produce ammonia and phosphoric acid, which activated the material and promoted the increase in the specific surface area and pore volume of the activated carbon. As an N and P source, the addition of diammonium hydrogen phosphate successfully achieved the N, P co-doping of activated carbon, and the introduction of N- and P-containing functional groups was the key to enhance the adsorption of La3+. Among them, graphitic nitrogen could provide interactions between La3+-π bonds, and C-P=O and C/P-O-P could provide active sites for the adsorption of La3+ through complexation and electrostatic interaction. The adsorption of La3+ on N, P co-doped activated carbons was endothermic and spontaneous, and the adsorption process conformed to the Langmuir isotherm and secondary kinetic model. Under the process conditions of an activation temperature of 900℃ and pH=6, the adsorption capacity of the N, P co-doped activated carbon was as high as 55.18 mg·g-1, which was 2.53 times higher than that of the undoped sample, and its adsorption selectivity for La3+ in the La3+/Na+and La3+/Ca2+ coexistence systems reached 93.49% and 82.49%, respectively. Additionally, the removal efficiency remained above 54% after five successive adsorption-desorption cycle experiments.

Waste biomass-derived N, P co-doping carbon aerogel-coated CoxFe1-xP with modulated electron density for efficient electrooxidation of contaminants.

Developing low-cost, green, high-performing electrode materials to address environmental pollutants and the energy crisis is significant but challenging. Herein, the bimetallic iron cobalt phosphide coated in waste biomass-derived N, P co-doping carbon (CoxFe1-xP@NPC) is constructed. Furthermore, the active site density and the water decomposition energy barrier of surface-coated NPC are modulated by optimizing the electronic structure of CoxFe1-xP via doping engineering. The Fe-modulated CoxFe1-xP@NPC exhibits a hierarchical porous self-supporting structure and excellent physical & chemical properties with excellent electrooxidation performance, achieving over 95% removal of TCH within 60 min. The density functional theory (DFT) calculations further confirms that N carries more positive charge and P carries more negative charge in the NPC of CoxFe1-xP@NPC with Fe modulation, which can promote the adsorption and dissociation of water molecules. Of note, Co0.75Fe025P@NPC displays a low water dissociation energy barrier to produce ·OH and a high energy barrier to produce O2 than its counterparts. This study offers new insight into controllable modulation of biomass carbon-based composite electrode catalytic activity for high-efficiency degradation of contaminants.

Phosphorus-Mediated Local Charge Distribution of N-Configuration Adsorption Sites with Enhanced Zincophilicity and Hydrophilicity for High-Energy-Density Zn-Ion Hybrid Supercapacitors.

Tailor-made carbonaceous-based cathodes with zincophilicity and hydrophilicity are highly desirable for Zn-ion storage applications, but it remains a great challenge to achieve both advantages in the synthesis. In this work, a template electrospinning strategy is developed to synthesize nitrogen and phosphorous co-doped hollow porous carbon nanofibers (N, P-HPCNFs), which deliver a high capacity of 230.7 mAh g-1 at 0.2 A g-1 , superior rate capability of 131.0 mAh g-1 at 20 A g-1 , and a maximum energy density of 196.10 Wh kg-1 at the power density of 155.53 W kg-1 . Density functional theory calculations (DFT) reveal that the introduced P dopants regulate the distribution of local charge density of carbon materials and therefore facilitate the adsorption of Zn ions due to the increased electronegativity of pyridinic-N. Ab initio molecular dynamics (AIMD) simulations indicate that the doped P species induce a series of polar sites and create a hydrophilic microenvironment, which decreases the impedance between the electrode and the electrolyte and therefore accelerates the reaction kinetics. The marriage of ex situ/in situ experimental analyses and theoretical simulations uncovers the origin of the enhanced zincophilicity and hydrophilicity of N, P-HPCNFs for energy storage, which accounts for the faster ion migration and electrochemical processes.

Highly Luminescent Nucleoside-Based N, P-Doped Carbon Dots for Sensitive Detection of Ions and Bioimaging.

The efficient detection of Fe3+ and MnO4 - in a water environment is very important and challenging due to their harmful effects on the health of humanity and environmental systems. Good biocompatibility, sensitivity, selectivity, and superior photophysical properties were important attributes of carbon dot-based CDs sensors for sensing applications. In this work, we synthesized N, P-co-doped carbon dots (N/P CDs) with guanosine 5'-monophosphate (GMP) as a green carbon source, with high fluorescence quantum yield in water (QY, 53.72%). First, the luminescent N/P CDs showed a three-state "on-off-on" fluorescence response upon the sequential addition of Fe3+ and F-, with a low detection limit of 12 nM for Fe3+ and 8.5 nM for F-, respectively. Second, the N/P CDs also exhibited desirable selectivity and sensitivity for toxic MnO4 - detection with the limit of detection of 18.2 nM, through a turn-off mechanism. Moreover, the luminescent N/P CDs successfully monitored the aforementioned ions in environmental water samples and in Escherichia coli.

One step synthesis of N, P co-doped hierarchical porous carbon nanosheets derived from pomelo peel for high performance supercapacitors.

Ammonium dihydrogen phosphate (NH4H2PO4) was used as an activator and co-dopant to induce the synthesis of N, P co-doped porous carbon nanosheets (NPCNs) from pomelo peel for using as high-performance supercapacitors. Pomelo peel has a unique sponge-like structure in which NH4H2PO4 particles can be evenly embedded. The pore structure and heteroatomic doping amount of NPCNs were controlled by adjusting the pyrolysis temperature. As a result, the optimal sample exhibits high specific capacitance (314 ± 2.6 F g-1) and rate capability (82% of capacitance retention at 20 A g-1). NPCNs-750 was further employed in a symmetrical supercapacitor (NPCNs-750//NPCNs-750 SSC) with 2 M Li2SO4 electrolyte, and exhibits a high energy density of 36 ± 1.5 W h kg-1 at a power density of 1000 W kg-1, with excellent cycling stability with 99% retention after 10,000 cycles. A series of excellent results show that this pollution-free and cost-effective method can be used for the design and preparation of high-performance supercapacitor electrode materials.

Boosting polysulfides immobilization and conversion through CoS2 catalytic sites loaded carbon fiber for robust lithium sulfur batteries.

The practical applications of lithium sulfur battery is impeded by the lithium polysulfide shuttling and sluggish redox kinetics. To address the issues, herein, a multifunctional host is developed by the combination of nitrogen, phosphorus co-doped carbon fiber (NPCF) and CoS2 towards boost the soluble polysulfides adsorption and transformation. Benefiting from the NPCF originated from biomass cattail fibers, a high conductive network is provided, and shuttle effect is reduced due to the strong chemical interaction between abundant heteroatom polar sites and lithium polysulfides. Moreover, the electrocatalytic CoS2 on the carbon skeleton facilitate lithium polysulfides conversion and lithium sulfide deposition based on the density functional theory calculations and experiments. The efficient lithium polysulfides entrapment and subsequent electrocatalytic conversion improve dynamic stability during cycling, especially for rate capability. With these advantageous features, the electrode with NPCF/CoS2 host can deliver a good rate capability (903 and 782 mAh g-1 at 1C and 2C, respectively) and stable cycling performance with an ultra-low capacity decay of 0.014% per cycle at 1C. Notably, the cell can achieve a high areal capacity of 4.96 mA h cm-2 under an elevated sulfur loading of 5.0 mg cm-2. Overall, the improvement on the electrochemical performance ascertains the validity of the design strategy based on synergy engineering, which is a highly suitable approach for energy storage and conversion application.

Nitrogen (N), Phosphorus (P)-Codoped Porous Carbon as a Metal-Free Electrocatalyst for N2 Reduction under Ambient Conditions.

The electrocatalytic conversion of nitrogen gas at ambient conditions represents a novel approach for ammonia synthesis to the sustainable society. It is critical to understand the detailed pathways and mechanisms of this promising process to develop a highly efficient catalyst. Herein, the N, P co-doping carbon (NP-C-MOF-5) catalyst was prepared for electrocatalytic N2 reduction in acid electrolytes under ambient temperatures and pressures. Experimental results showed that there are two products including NH3 and N2H4·H2O on the NP-C-MOF-5 cathode at -0.1 V versus RHE with the yield of 1.08 and 5.77 × 10-4 µg h-1 mgcat.-1, respectively. Moreover, an electrocatalytic pathway on NP-C-MOF-5 was investigated by the electrochemical in situ Fourier transform infrared technique. The results confirmed the formation of N2H y (1 ≤ y ≤ 4) intermediates on NP-C-MOF-5 cathode surfaces, suggesting an associative pathway for the N2 reduction reaction.

Effects of N mono- and N/P dual-doping on H2O2, OH generation, and MB electrochemical degradation efficiency of activated carbon fiber electrodes.

Pure N mono- and N/P dual-doped cotton-stalk-derived activated carbon fibers (CSCFs) were synthesized by steam, HNO3(CSCF-N), NH3(CSCF-A), and (NH4)3PO4(CSCF-N/P) treatments. This study investigated how three different N/P modifiers affected the pore structure, chemical property, H2O2 generation ability, and electrocatalytic activity of methylene blue (MB) degradation of CSCFs in an electric-Fenton system. Results confirmed that the three employed treatments effectively doped N/P in the carbon lattice and slightly changed the pore structures. NH3 and (NH4)3PO4 were the most effective modifiers for the N mono-doping and N/P dual-doping of CSCFs, respectively. Among the fabricated CSCFs, the N/P dual-doped CSCF-N/P demonstrated the highest electrochemical activity in an electro-Fenton system, followed by the N mono-doped CSCF-A, the CSCF-N, and the raw CSCF. In contrast to the CSCF electrode, the CSCF-N/P electrode exhibited enhanced H2O2, OH generation, and MB degradation efficiency by 42%, 41%, and 35%, respectively. Under optimum conditions, the electrochemical decolorization efficiency of MB (initial concentration, 100 mg L-1) of the CSCF-N/P reached 93% after 150 min and was 24.1% higher than that of the CSCF. By the tenth cycle, 82.2% of the MB could still be decomposed, suggesting the excellent stability and reusability of the N/P co-doped CSCF electrode. The outstanding electrocatalytic performance of the CSCF-N/P electrode is primarily due to the simultaneous doping of active N/P sites with low activation energy and introduction of mesopores with strong trapping forces for MB. The MB reduction catalyzed by CSCF electrodes followed pseudo-first-order kinetics, and the reaction rate depended on the modifiers.

Adenosine-derived doped carbon dots: From an insight into effect of N/P co-doping on emission to highly sensitive picric acid sensing.

The various synthetic routes of carbon dots (C-dots) feature a considerable step toward their potential use in chemical sensors and biotechnology. Herein, by coupling phosphorus and nitrogen element introduction, the adenosine-derived N/P co-doped C-dots with fluorescence enhancement were achieved. By separately employing adenosine, adenosine monophosphate, adenosine diphosphate, and adenosine-5'-triphosphate as precursors, the effect of N/P co-doping on the fluorescence emission is discussed in detail. The formed C-dots with adenosine monophosphate exhibited strong blue fluorescence with a high quantum yield of 33.81%. Then the C-dots were employed as a fluorescent probe and utilized to develop a fast, sensitive, and selective picric acid sensor. The fluorescence of C-dots can be quenched by picric acid immediately, giving rise to a picric acid determination down to 30 nM. The possible mechanism of fluorescence quenching was discussed, which was proved to be inner filter effect and static quenching. Moreover, this method has the potential to detect picric acid in environmental water samples.