Inherent mass transfer engineering of a Co,N co-doped carbon material towards oxygen reduction reaction

Oxygen reduction reaction (ORR) is an important process for the conversion and utilization of a wide range of renewable energy sources, and is critical for the shape of future energy scenario [1–10]. However, ORR is a complex four-electron transfer process and is kinetically sluggish. It is urgent to develop high-efficient electrocatalysts to solve this problem [11–15]. Up to now, precious metal-based catalysts such as Pt-based electrocatalysts have been widely studied and found to be one of the most efficient electrocatalysts for ORR. However, the high price and the small reserves limit their large-scale commercialization [10,16–23]. Therefore, in order to fulfill needs for the practical applications, it is necessary to develop low-cost electrocatalysts, also with high activity and great stability [19,24–28].

Edge-enriched N, S co-doped hierarchical porous carbon for oxygen reduction reaction

The development of carbon materials with high electrochemical performance for next-generation energy device is emerging, especially N, S co-doped carbon materials have sparked intensive attention. However,the exploration of N, S co-doped carbon with well-defined active sites and hierarchical porous structures are still limited. In this study, we prepared a series of edge-enriched N, S co-doped carbon materials through pyrolysis of thiourea(TU) encapsulated in zeolitic imidazolate frameworks(TU@ZIF) composites,which delivered very good oxygen reduction reaction(ORR) performance in alkaline medium with onset potential of 0.94 V vs. reversible hydrogen electrode(RHE), good stability and methanol tolerance. Density functional theory(DFT) calculations suggested that carbon atoms adjacent to N and S are probable active sites for ORR intermediates in edge-enriched N, S co-doped carbon materials because higher electron density can enhance O_(2)adsorption, lower formation barriers of intermediates, improving the ORR performance comparing to intact N, S co-doped carbon materials. This study might provide a new pathway for improving ORR activity by the integration engineering of edge sites, and electronic structure of heteroatom doped carbon electrocatalysts.

Hierarchical porous nitrogen,oxygen,and phosphorus ternary doped hollow biomass carbon spheres for high-speed and long-life potassium storage

Limited lithium resources have promoted the exploration of new battery technologies.Among them,potassium-ion batteries are considered as promising alternatives.At present,commercial graphite and other carbon-based materials have shown good prospects as anodes for potassium-ion batteries.However,the volume expansion and structural collapse caused by periodic K+insertion/extraction have severely restricted further development and application of potassium-ion batteries.A hollow biomass carbon ball(NOP-PB)ternarily doped with N,O,and P was synthesized and used as the negative electrode of a potassium-ion battery.X-ray photoelectron spectroscopy,Fourier‐transform infrared spectroscopy,and transmission electron microscopy confirmed that the hollow biomass carbon spheres were successfully doped with N,O,and P.Further analysis proved that N,O,and P ternary doping expands the interlayer distance of the graphite surface and introduces more defect sites.DFT calculations simultaneously proved that the K adsorption energy of the doped structure is greatly improved.The solid hollow hierarchical porous structure buffers the volume expansion of the potassium insertion process,maintains the original structure after a long cycle and promotes the transfer of potassium ions and electrons.Therefore,the NOP‐PB negative electrode shows extremely enhanced electrochemical performance,including high specific capacity,excellent long‐term stability,and good rate stability.

MnO_(2) nanosheet modified N, P co-doping carbon nanofibers on carbon cloth as lithiophilic host to construct high-performance anodes for Li metal batteries

Lithium (Li) metal batteries have attracted much attention owing to its ultra-high energy density.However,as important part of Li metal batteries,Li anodes still face many challenges,mainly including uncontrolled dendritic Li formation,dramatical volume variation and serious pulverization.Herein,manganese dioxide (MnO_(2)) nanosheet modified nitrogen (N),phosphorus (P) co-doping carbon nanofibers(NPC) on carbon cloth (CC)(MnO_(2)@NPC-CC) is successfully fabricated through electrodeposition approach and further treated with Li by the molten-infusion method to prepare Li based Mn@NPC-CC(Li-Mn@NPC-CC) electrode.The synergy of MnO_(2) and NPC obviously increases the reaction rate between MnO_(2)@NPC-CC and Li and guides even Li distribution over infusion process.Additionally,theoretical calculation,simulation and experimental results further indicate that N,P,Mn multi-doping effectively improves the superior lithiophilicity of Li-Mn@NPC-CC,which induces uniform Li deposition/dissolution to suppress dendrite growth over cycles.Moreover,conductive and porous NPC matrix not only effectively improves the stability of Li-Mn@NPC-CC,but also provides abundant spaces to accelerate the transfer of ion/electron and buffer electrode dimension variation during cycling.Hence,Li-Mn@NPC-CC-based symmetric cells exhibit extra-long cycling life (over 2200 h) with small hysteresis of 20 mV.When the LiMn@NPC-CC anode couples with air,Li iron phosphate (LiFePO_(4)),or hard carbon (C) cathode,the assembled full cells exhibit outstanding performance with low hysteresis and stable cycling properties.Especially,the corresponding pouch-typed Li–air cells also exhibit good performance at different bending angles and even power a series of electronic devices.

Boron and nitrogen co-doped porous carbon derived from sodium alginate enhanced capacitive deionization for water purification

Capacitive deionization can alleviate water shortage and water environmental pollution, but performances are greatly determined by the electrochemical and desalination properties of its electrode materials. In this work, B and N co-doped porous carbon with micro-mesoporous structures is derived from sodium alginate by a carbonization, activation, and hydrothermal doping process, which exhibits large specific surface area (2587 m^(2)·g^(‒1)) and high specific capacitance (190.7 F·g^(‒1)) for adsorption of salt ions and heavy metal ions. Furthermore, the materials provide a desalination capacity of 26.9 mg·g−1 at 1.2 V in 500 mg·L^(‒1) NaCl solution as well as a high removal capacity (239.6 mg·g^(‒1)) and adsorption rate (7.99 mg·g^(‒1)·min^(‒1)) for Pb2+ with an excellent cycle stability. This work can pave the way to design low-cost porous carbon with high-performances for removal of salt ions and heavy metal ions.

Synergistic Effect of Nitrogen/Phosphorus Co-Doping and Molybdenum Carbide Induced Electron Redistribution of Carbon Layer to Boost Hydrogen Evolution Reaction

The development of highly efficient non-precious-metal-based electrocatalysts for the hydrogen evolution reaction is imperative for promoting the large-scale application of electrochemical water splitting.Herein,nitrogen/phosphorus co-doped carbon nanorods encapsulated Mo_(2)C nanoparticles(Mo_(2)C@PNc)have been prepared by pre-phosphating treatment in combination of the coordination with polydopamine and the subsequent pyrolysis.The phosphating temperature has a significant effect on the content of phosphorus within the resultant Mo_(2)C@PNC,and the optimal catalyst delivers superior HER activity with the low overpotential of 104 mV at a current density of 10 mAcm^(-2) and good stability for 8 h,which has been theoretically demonstrated to originate from the synergistic effect between P doping and Mo_(2)C induced electron redistribution of nitrogen-doped carbon layer.

Molten Salts Strategy for the Synthesis of CoP Nanoparticles Entrapped,N,P co-Doped Mesoporous Carbons as Electrocatalysts for Hydrogen Evolution

Amolten salt process was developed to prepare CoP nanoparticles(NPs) embedded, N,P co-doped carbons with the combination of hand milling and high temperature carbonization. The characterization results implied that the as-prepared samples possessed mesoporous structures. Moreover, the mass ratios of the precursors affected the crystalline structures and the porosities of the final electrocatalysts. The as-prepared catalysts exhibited excellent electrocatalytic performances towards hydrogen evolution reaction(HER) under acidic and alkaline conditions. The as-prepared samples were designed as GxMyCoz, where x, y and z meant the amounts of glucose, melamine and CoCl2, respectively. The optimum sample of G6.0M2.0Co5.0 showed the best HER property with a low onset overpotential and a small Tafel slope, as well as excellent electrocatalytic stability.

Self-sacrificial template synthesis of Fe, N co-doped porous carbon as efficient oxygen reduction electrocatalysts towards Zn-air battery application

Designing highly efficient non-precious based electrocatalysts for oxygen reduction reaction(ORR) is of significance for the rapid development of metal-air batteries.Herein,a hydrothermal-pyrolysis method is employed to fabricate Fe,N co-doped porous carbon materials as effective ORR electrocatalyst through adopting graphitic carbon nitride(g-C_(3)N_(4)) as both the self-sacrificial templates and N sources.The gC_(3)N_(4)provides a high concentration of unsaturated pyridine-type N to coordinate with iron to form Fe-N active sites.Through adjusting the Fe doping amounts,it is proved that appropriate Fe doping content is conducive to the construction of abundant defects and active sites of Fe-N.The as-prepared catalyst exhibits superior electrocatalytic ORR performance in alkaline media with half-wave potential(E_(1/2)=0.82 V) and onset potential(E_(onset)=0.95 V),equivalent to the commercial Pt/C catalyst.Moreover,there is almost no activity loss after 10 k continuous cyclic voltammetry cycles and methanol tolerance,indicating the excellent durability and superior methanol tolerance.Remarkably,when assembled as the cathode in a Zn-air battery,the device displays a power density of 99 mW/cm^(2),an open-circuit potential of 1.48 V and long-term discharge-charge cycling stability,indicating the promising potential to substitute the Pt catalyst for practical application.

Highly N/O co-doped ultramicroporous carbons derived from nonporous metal-organic framework for high performance supercapacitors

A new nonporous Zn-based metal-organic framework(NPMOF) synthesized from a high nitrogencontaining rigid ligand was converted into porous carbon materials by direct carbonization without adding additional carbon sources.A series of NPMOF-derived porous carbons with very high N/O contents(24.1% for NPMOF-700,20.2% for NPMOF-800,15.1% for NPMOF-900) were prepared by adjusting the pyrolysis temperatures.The NPMOF-800 fabrica ted electrode exhibits a high capacitance of220 F/g and extremely large surface area normalized capacitance of 57.7 μF/cm~2 compared to other reported MOF-derived porous carbon electrodes,which could be attributed to the abundant ultramicroporosity and high N/O co-doping.More importantly,symmetric supercapacitor assembled with the MOF-derived carbon manifests prominent stability,i.e.,99.1 % capacitance retention after 10,000 cycles at 1.0 A/g.This simple preparation of MOF-derived porous carbon materials not only finds an application direction for a variety of porous or even nonporous MOFs,but also opens a way for the production of porous carbon materials for superior energy storage.

Interconnected N/P co-doped carbon nanocage as high capacitance electrode material for energy storage devices

Heteroatom doping carbon materials exhibit a huge application potential for energy storage devices(ESDs).Herein,interconnected N/P co-doped carbon nanocage(NP-CNC)was synthesized from pyrene molecules by using nano-MgO as template and melamine-phytic acid supramolecular aggregate as dopant coupled with KOH activation.The as-prepared NP-CNC possesses interconnected nanocages for electron transportation and abundant micropores for ion adsorption.Moreover,co-doped N/P species in NP-CNC provide active sites and additional pseudocapacitance.Consequently,NP-CNC as electrode material for symmetric supercapacitor exhibits a high gravimetric capacitance of 435 F·g^(-1) at 0.05 A·g^(-1),high volumetric capacitance of 274 F·cm^(-3) at 0.032 A·cm^(-3),and long cycle lifespan with 96.1%capacitance retention after 50,000 cycles.Furthermore,NP-CNC as cathode for zinc-ion hybrid supercapacitor delivers satisfactory energy and power densities of 130.6 Wh·kg^(-1)(82.3 Wh·L^(-1))and 14.4 kW·kg^(-1)(9.1 kWL^(-1)).This work paves a promising approach to the preparation of high capacitance NP-CNC for ESDs.

N,O co-doped porous carbon with rich pseudocapacitive groups exhibiting superior energy density in an acidic 2.4 V Li_(2)SO_(4)electrolyte

Designing a carbon material with a unique composition and surface functional groups for offering high specific capacity in a wide voltage window is of great significance to improve the energy density for the supercapacitor in a cheap and eco-friendly aqueous electrolyte.Herein,we develop an efficient strategy to synthesize a N,O co-doped hierarchically porous carbon(NODPC-1.0)with moderate specific surface area and pore volume as well as rich heteroatoms using a deep eutectic solvent(DES)as an activator.It is found that NODPC-1.0 with a large proportion of pseudocapacitive functional groups(pyrrole-N,pyridineN and carbonyl-quinone)can work stable in an acidic 2 mol/L Li_(2)SO_(4)(pH 2.5)electrolyte,exhibiting specific capacities of 375 and 186 F/g at the current densities of 1.0 and 100 A/g,respectively.Also,the assembled symmetric capacitor using the NODPC-1.0 as the active material and 2 mol/L acidic Li_(2)SO_(4)(pH 2.5)as the electrolyte shows an outstanding energy density of 74.4 Wh/kg at a high power density of 1.44 k W/kg under a broad voltage window(2.4 V).Relevant comparative experiments indicate that H+of the acidic aqueous electrolyte plays a crucial part in enhancement the specific capacity,and the abundant pseudocapacitive functional groups on the surface of the NODPC-1.0 sample play the key role in the improvement of electrochemical cycle stability under a broad voltage window.

A high-performance potassium-ion capacitor based on a porous carbon cathode originated from the Aldol reaction product

Potassium-ion capacitors(KICs) emerge as a promising substitute for the well-developed lithium-ion capacitors(LICs),however,the energy density of KICs is below expectations because of lacking a suitable electrical double-layer positive electrode.Using chemical activation of the Aldol reaction product of acetone with KOH,we synthesized a porous ca rbon with a Brunauer-Emmett-Teller surface area of up to 2947 m2/g and a narrow pore size distribution ranging from 1 nm to 3 nm.Half-cell(versus potassium metal) test demonstrates that this porous carbon has high capacitive performance in K+ based organic electrolytes.Furthermore,a novel KIC fabricated by this porous carbon as the cathode,yields high values of energy density and power density.The processes used to make this porous carbon are readily low-cost to fabricate metal-ion capacitors.

FeNi doped porous carbon as an efficient catalyst for oxygen evolution reaction

Polymer-derived porous carbon was used as a support of iron and nickel species with an objective to obtain an efficient oxygen reduction reaction(OER)catalyst.The surface features were extensively characterized using X-ray diffraction,X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy.On FeNi-modified carbon the overpotential for OER was very low(280 mV)and comparable to that on noble metal catalyst IrO_(2).The electrochemical properties have been investigated to reveal the difference between the binary alloy-and single metal-doped carbons.This work demonstrates a significant step for the development of low-cost,environmentally-friendly and highly-efficient OER catalysts.

1.82 wt.% Pt/N, P co-doped carbon overwhelms 20 wt.% Pt/C as a high-efficiency electrocatalyst for hydrogen evolution reaction

Cost-effective electrocatalysts for the hydrogen evolution reaction （HER） play a key role in the field of renewable energy. Although tremendous efforts have been devoted to the search of alternative materials, Pt/C is still the most efficient electrocatalyst for the HER. Nevertheless, decreasing the loading of Pt in the designed eletrocatalysts is of significance. However, with low Pt loading, it is challenging to maintain excellent catalytic performance. Herein, a new catalyst （Pt/NPC） was prepared by dispersing Pt nanoparticles （PtNPs） with an average diameter of 1.8 nm over a three-dimensional （3D） carbon network co-doped with N and P. Because of the high electronegativity of the N and P dopants, PtNPs were uniformly dispersed on the carbon network via high electronic affinity between Pt and carbon, affording a Pt/NPC catalyst; Pt/NPC exhibited superior HER activity, attributed to the down-shift of the Pt d-band caused by the donation of charge from N and P to Pt. The results show that Pt/NPC with an ultralow Pt loading of 1.82 wt.% exhibits excellent HER performance, which corresponds to a HER mass activity 20.6-fold greater than that observed for commercial 20% Pt/C at an overpotential of 20 mV vs. RHE.

Binary doping of nitrogen and phosphorus into porous carbon: A novel di-functional material for enhancing CO_(2) capture and super-capacitance

Designing of hetero-atomic doped carbon-based systems through pyrolysis of abundant element organic precursors is a novel approach to construct rational porous carbon materials.Herein,a highly-cross-linked triazine polymer is employed to fabricate N,P co-doped porous carbon(A-TDP-12)with tunable active nitrogen in the carbon framework for simultaneous enhancement of CO_(2) capture capability and Supercapacitance(SC).The synthesized A-TDP-12 possesses a typical hierarchically porous framework(micro-pores and meso-pores)with a large surface area(1332 m^(2) g^(-1))and a rich content of N(7.89 at.%)and P(0.74 at.%).It delivers a CO_(2) adsorption capacity of 1.52 and 5.68 mmol g^(-1) at 1 and 5 bar,respectively,with almost no decay after successive 8 recycles.In 6 M KOH aqueous electrolyte,A-TDP-12 exhibits a superior specific capacitance of 172.7 F g^(-1) at a current density of 1 A g^(-1).Even at a high current density of 10 A g^(-1),80%of its initial capacity still remains.This work not only offers a novel strategy for fabricating promising adsorbents and electrodes for CO_(2) uptake and SCs,but also provides new insights into design of porous carbon material for related applications.

Bismuth stabilized by ZIF derivatives for electrochemical ammonia production:Proton donation effect of phosphorus dopants

N2 electroreduction reaction(NRR)offers a feasible and promising alternative for NH_(3)production by using clean energy sources.However,it is still obstructed by the pretty low NH3 yield rate and Faradaic efficiency(FE)primarily due to the undesired competing hydrogen evolution reaction and the extremely stable N≡N bond.Herein,bismuth nanoparticles were successfully embedded in N and P co-doped carbon nanoflakes(Bi/NPC)by high-temperature pyrolyzation of Bi-zeolitic imidazole frameworks(ZIF)followed by phosphorization,and used as a high-efficiency catalyst toward N2 electroreduction to NH3.In 0.1 M KHCO_(3)electrolyte,Bi/NPC exhibits excellent NRR performances,including a high NH3 yield rate of 3.12μg·h^(−1)·cm^(−2)(−0.6 V vs.reversible hydrogen electrode(RHE)),an outstanding FE of 13.58%(−0.4 V vs.RHE),and a remarkable stability up to 36 h under ambient conditions.This outstanding NRR catalytic activity is mainly attributed to the intrinsic electrocatalytic NRR activity combined with the inert hydrogen evolution reaction(HER)activity of Bi,the adsorption and activation of N2 facilitated by N dopants,as well as the superior conductivity and the large specific surface area of the two-dimensional layered carbon matrix.Notably,the hydrogen source provided by P dopant promotes the hydrogenation of the adsorbed N,which further boosts the NRR performance in alkaline electrolyte.The ultralong durability of Bi/NPC is attributed to the highly dispersed bismuth catalytic active centers confined in the skeleton of N and P co-doped carbon nanoflakes,which inhibits the agglomeration of bismuth centers.This work presents a novel avenue for designation and fabrication of high-performance Bi-based electrocatalysts for NRR.