Exploring highly active, stable, and inexpensive electrocatalysts for the oxygen reduction reaction (ORR) is pivotal in developing high-performance energy conversion devices. Moreover, the production of catalysts containing transition metals with the appropriate nitrogen doping level is a potential approach to increase ORR catalytic efficiency, especially under acidic conditions. In this study, a hierarchical graphitic porous carbon-containing Fe and N was obtained via pyrolysis of a bimetal MOF (Fe/ZIF-8) composited with pyrrole. Further experimental and theoretical results confirmed that the synergistic effects between Fe-based nanoparticles and N-doping in the networks are likely form one of the main reasons for better ORR performance. Under optimized conditions, the resultant Fe-bNCNT/NC-900 (iron-based nanoparticles enwrapped in bamboo-like nitrogen-doped carbon nanotubes (bNCNTs) grown on N-doped sheet-like carbon) exhibits high electrocatalytic activity, high selectivity (direct 4e– reduction of oxygen to water), and stability in both acidic and alkaline electrolytes. Under acidic conditions, the half-wave potential (E 1/2 = 0.770 VRHE) of Fe-bNCNT/NC-900 is comparable to commercial Pt/C (E 1/2 = 0.800 VRHE). However, this catalyst shows better activity with a half-wave potential of 0.920 VRHE, which is more than Pt/C (E 1/2 = 0.880 VRHE) in an alkaline electrolyte. The E 1/2 of Fe-bNCNT/NC-900 under acidic and alkaline conditions experienced a 170 and 28 mV loss after 20 000 continuous cycles, and these results show the prepared catalyst has promising stability.
The electronic properties, adsorption energies and energy barrier of sodium ion diffusion in B-doped graphyne (BGY) are studied by density functional theory (DFT) method.
In this work, by density functional theory (DFT) calculations, sp−sp 2hybridized boron-doped graphdiyne (BGDY) nanosheets have been investigated as an anode material for sodium storage. The density of states (DOS) and band structure plots show that substituting a boron atom with a carbon atom in an 18-atom unit cell converts the semiconductor pristine graphdiyne (GDY) to metallic BGDY. Also, our calculations indicate that, due to the presence of boron atoms, the adsorption energy of BGDY is more than that of GDY. The diffusion energy barrier calculations show that the boron atom in BGDY creates a more suitable path with a low energy barrier for sodium movement. This parameter is important in the rate of charge/discharge process. On the other hand, the projected density of states (PDOS) plots show that sodium is ionized when adsorbed on the electrode surface and so Na−BGDY interaction has an electrostatic character. This type of interaction is necessary for the reversibility of adsorption in the discharge mechanism. Finally, the calculation of the theoretical capacity shows an increase in BGDY (872.68 mAh g −1 ) in comparison with that in GDY (744 mAh g −1 ). Thus, from comparison of different evaluated parameters, it can be concluded that BGDY is a suitable anode material for sodium-ion batteries.
But still, there are many challenging questions about limited sources of lithium in the world, the high cost of lithium, lifetime, safety, and performance in lowtemperature. [9][10][11][12][13] Because of the extent of sodium resources in the world and the low price of this element compared with lithium, SIBs have attracted plenty of attention in EESs. [10,[14][15][16] So, trying to find, synthesize, or computational design suitable anode materials to improve SIBs is indispensable.The large radius of sodium ion (1.07 Å) compared with lithium ion (0.76 Å) can have a devastating effect on sodium storage and reaction kinetic. So, some materials, such as graphite, cannot be able to store sodium. [17,18] Like 2D materials, carbon nanotubes (1D materials) have a high surface/volume ratio and sodium storage capacity. Many researchers have considered nanotube-based anode materials because of their high energy density, proper cyclability, and high capacity. [18] Such as MXene/Carbon Nanotube Composite (421 mAh g −1 ), [19] pine-needle-like CuS (522 mAh g −1 ), [20] coreshell heterostructure of MWCNT@GONR (317.93 mAh g −1 ), [13] sodium titanate nanotubes (93 mAh g −1 ), [21] Sb@C coaxial nanotubes (407 mAh g −1 ), [22] N, P dual-doped carbon nanotube (180.3 mAh g −1 ), [23] MoS 2 @C Nanotubes (480 mAh g −1 ), [24] ZnSe/MWCNT composites (382 mAh g −1 ), [25] bismuth nanorods encapsulated in N-doped carbon nanotubes, [26] and nitrogendoped bamboo-like carbon nanotubes (270 mAh g −1 ), [27] etc.Biphenylene (BP) nanosheet, a nonbenzenoid carbon allotrope with an sp 2 framework, was synthesized in 2021 by Fan et al. [28] It has an orthorhombic lattice [29,30] that is composed of four, six, and eight atomic rings with metallic characters. [28,31] This structure and its derivatives were investigated by many researchers in different fields. Al-Jayyousi et al. [32] investigated BP and its defective structure as anchoring materials for lithium-sulfur batteries by density functional theory (DFT) calculations. They have indicated that with defect creation, the adsorption and migration of lithium polysulfide (LiPSs) are improved. Ferguson et al. [29] studied the lithium storage on BP nanosheets. They found that this structure shows acceptable volume changes and has high capacity as electrode material for LIBs. The dynamical, mechanical and thermal stability of BP was confirmed by Han et al. [33] They illustrated that the metallic feature, low diffusion energy barrier, and capacity of The properties of pristine and boron-doped biphenylene nanotubes (BPNT and BBPNT, respectively) as anode materials for sodium storage are studied using density functional theory (DFT). To this end, the electronic properties, adsorption energy, diffusion energy barrier, open-circuit voltage (OCV), and theoretical capacity are evaluated. The density of states calculations indicate that BPNT and BBPNT with zero band gap have a metallic character, which is critical for electron transferring in electrode materials. The calculation of adsorption energies sugges...
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