Fabrication of Fe Nanoparticles into N-doped Mesoporous Carbon Nanotube Derived from Rice-Like Fe/N-MOF and Its ORR Catalytic Performance for MFC

The development of non-noble metal oxidation reduction catalysts(ORR)to improve microbial fuel cell(MFC)performance remains extremely challenging.Herein,the nitrogen-doped iron-based porous carbon nanotube Fe/N@MC-T ORR catalysts were derived from Fe/N-MOF by pyrolyzation using acetonitrile as the nitrogen precursor in a low-cost organic solvent.The Fe/N@MC-T catalysts under different pyrolysis temperatures were characterized by SEM,TEM,BET,XRD,and XPS techniques.Fe/N-MOF showed a smooth rice-like structure with a particle size of about 400×50 nm^(2).The Fe species in Fe/N@MC-T mainly exists in the form of zero-valent iron with a small amount of Fe3C.The results of electrochemical tests revealed that the onset and half-wave potentials of Fe/N@MC-700 were 0.89 V and 0.80 V,respectively,which were only slightly lower than those of the commercial Pt/C(0.92 V and 0.82 V).The MFC with Fe/N@MC-700 showed a highest power density of 864.1 mW/m^(2),which was about 2.25 times that of MFC with carbon cloth,and was slightly lower than that of MFC with Pt/C(20%)(1002.0 mW/m^(2)),which demonstrated that the Fe particles wrapped in carbon nanotubes possessed a relatively high ORR activity.

Ozone-Mediated Functionalization of Multi-Walled Carbon Nanotubes and Their Activities for Oxygen Reduction Reaction

The functionalization of multi-walled carbon nanotubes （MWCNTs） by ozone treatment has been sys- tematically investigated by using Raman spectroscopy, transmission electron microscopy （TEM）, Fourier transform inhared spectroscopy （FTIR）, X-ray photoelectron spectroscopy （XPS）, organic elemental anal- ysis （OEA） and Boehm titration. The results showed that the functionalization process occurred at defective sites （opened mouths, tube caps, debris, etc.） before opening caps and truncating walls, and finally the graphitic structure was deteriorated. The surface oxygen content first increased with the treatment time but kept at around 8.0 wt% after 5 h. The analysis of the distribution of oxygen-containing groups re- vealed that phenolic hydroxyl was gradually converted to carboxyl and lactone, The carboxyl was found to play a pivotal role to reduce the over-potentials when we used the functionalized MWCNTs as the cat- alyst for oxygen reduction reaction （ORR）.

MoC nanocrystals confined in N-doped carbon nanosheets toward highly selective electrocatalytic nitric oxide reduction to ammonia

Electrochemical nitric oxide reduction reaction(NORR)to produce ammonia(NH3)under ambient conditions is a promising alternative to the energy and carbon-intensive Haber–Bosch approach,but its performance is still improved.Herein,molybdenum carbides(MoC)nanocrystals confined by nitrogen-doped carbon nanosheets are first designed as an efficient and durable electrocatalyst for catalyzing the reduction of NO to NH3 with maximal Faradaic efficiency of 89%±2%and a yield rate of 1,350±15μg·h^(−1)·cm^(−2) at the applied potential of−0.8 V vs.reversible hydrogen electrode(RHE)as well as high stable activity with negligible current density and NH3 yield rate decays over a 30 h continue the test.Moreover,as a proof-of-concept of Zn–NO battery,it achieves a peak power density of 1.8 mW·cm^(−2) and a large NH3 yield rate of 782±10μg·h^(−1)·cm^(−2),which are comparable to the best-reported results.Theoretical calculations reveal that the MoC(111)has a strong electronic interaction with NO molecules and thus lowering the energy barrier of the potential-determining step and suppressing hydrogen evolution kinetics.This work suggests that Mo-based materials are a powerful platform providing great opportunities to explore highly selective and active catalysts for NH3 production.

Electrocatalytic reduction of NO to NH_(3) in ionic liquids by P-doped TiO_(2) nanotubes

Designing advanced and cost-effective electrocatalytic system for nitric oxide(NO)reduction reaction(NORR)is vital for sustainable NH_(3) production and NO removal,yet it is a challenging task.Herein,it is shown that phosphorus(P)-doped titania(TiO_(2))nanotubes can be adopted as highly efficient catalyst for NORR.The catalyst demonstrates impressive performance in ionic liquid(IL)-based electrolyte with a remarkable high Faradaic efficiency of 89%and NH3 yield rate of 425μg·h^(−1)·mg_(cat).^(−1),being close to the best-reported results.Noteworthy,the obtained performance metrics are significantly larger than those for N_(2) reduction reaction.It also shows good durability with negligible activity decay even after 10 cycles.Theoretical simulations reveal that the introduction of P dopants tunes the electronic structure of Ti active sites,thereby enhancing the NO adsorption and facilitating the desorption of ^(*)NH_(3).Moreover,the utilization of IL further suppresses the competitive hydrogen evolution reaction.This study highlights the advantage of the catalyst−electrolyte engineering strategy for producing NH_(3) at a high efficiency and rate.

Anchor single atom in h-BN assist NO synthesis NH_(3):a computational view

Synthesis of ammonia gas through environmental protection and low-cost electrocatalysis is one of the ways to solve the current human energy problems.Herein,through the study of density functional theory(DFT),a series of transition metal single atoms are embedded in the defect-containing h-BN to construct a TM@B_(2) N_(2)(TM=Ti-Zn,Nb-Ag) two-dimensional nanostructure.The activation effect of these single-atom catalysts on NO molecules and the electrochemical performance of catalyzing NO reduction reaction(NORR)were explored.All reaction pathways are studied in detail,and competition between hydrogen proton and ammonia(NH3) oxidation with NORRs is also explored.Among the16 transition metal atoms we studied,the intercalation of Pb atom into h-BN has the best catalytic activity.The reaction rate-limiting potential of NORR is only 0.55 eV,and the surface HER reaction and ammonia oxidation can be effectively inhibited.It is hoped that our research can further promote the application of h-BN in the field of catalysis and provide some guidance for experimental workers in the field of ammonia synthesis.

An acetic acid refluxing-electrochemistry combined strategy to activate supported-platinum electrocatalysts

Surfactant removal from the surface of platinum-based nanoparticles prepared using solution-based methods is a prerequisite to realize their high catalytic performance for electrochemical reactions. Herein, we report an effective approach combining acetic acid refluxing with an electrochemical process for the removal of amine- or thiol-based capping agents from the surface of supported-platinum nanoparticles. This strategy involves surfactant protonation by refluxing the supported-platinum particles in acetic acid followed by surfactant removal by subsequent electrochemical treatment at high potential. We demon- strate that this combined activation process is essential to enhance platinum particle performance in catalyzing direct methanol fuel cell reactions, including methanol oxidation and oxygen reduction reac- tions. The studies in this work show promise in electrocatalysis applications of solution-based materials synthesis.