Direct solid-state growth of Fe/N Co-doped coordination structure between carbon nanotubes and ultra-thin porous carbon nanosheets towards oxygen reduction reaction

Strontium doped Fe-based porous carbon for highly efficient electrocatalytic ORR and MOR reactions

The catalytic activity improvement of Fe-based active sites derived from metal organic frameworks toward oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) remains a major challenge. In this study, the growth of strontium decorated 2-methylimidazole zinc salt (Sr/ZIF-8) is prepared as a carrier to vapor deposited iron formation Sr doped Fe-based nitrogen-doped carbon framework (named as Sr/FeNC). After high-temperature pyrolysis and vapor deposition, strontium carbonate nanocrystals are evenly dispersed on the shrunk dodecahedron carbon frame and multitudinous Fe-based active catalytic sites are embedded in carbon skeleton. The optimal Sr/FeNC-2 catalyst demonstrates the outstanding ORR performance in terms of a half-wave potential of 0.851 V and an onset potential of 0.90 V, while Sr/FeNC-2 exhibits a high current density of 18.2 mA cm-2 and a lower Tafel slope of 21 mV dec-1 in MOR. The exceptional catalytic activity could be ascribed to the synergistic coupling effect of strontium compounds with Fe-based catalytic sites (Fe-Nx, Fe, and iron oxide). In particular, the formation of SrCO3 affects the bonding configuration of the iron species sites, leading to an optimization of the electronic structure within the multihole carbon matrix. The synthetic approach presents a prospective strategy for future endeavors in developing innovative and advanced bifunctional catalysts for ORR and MOR.

Confined Co@NCNTs as highly efficient catalysts for activating peroxymonosulfate: free radical and non-radical co-catalytic mechanisms

A series of transition metal (Co, Ni, Fe) nanoparticles were confined in N-doped carbon nanotubes (NCNTs) prepared (Co@NCNTs, Ni@NCNTs, and Fe@NCNTs) by the polymerization method. The structure and composition of catalysts were well characterized. The catalytic activity of catalysts for activating peroxymonosulfate (PMS) was conducted via acid orange 7 (AO7) degradation. Among the catalysts, Co@NCNTs performed the best catalytic activity. Additionally, Co@NCNTs performed good catalytic activity in pH values of 2.39-10.98. Cl- and SO42- played a promoting roles in AO7 degradation. NO3- presented a weak effect on the catalytic performance of Co@NCNTs, while HCO3- and CO32- significantly suppressed the catalytic performance of Co@NCNTs. Both non-radical (1O2 and electron transfer) and free-radical (·OH and SO4·-) pathways were detected in the Co@NCNTs/PMS system. Notably, 1O2 was identified to be the main active specie in this study. The catalytic activity of Co@NCNTs gradually decreased after cycle reuse of Co@NCNTs. Finally, the toxicity of the AO7 degradation solution in the study was evaluated by Chlorella pyrenoidosa.

Noble-Metal-Free FeMn-N-C Catalyst for Efficient Oxygen Reduction Reaction in Both Alkaline and Acidic Media

The oxygen reduction reaction (ORR) is important cathodic reaction running in several electrochemical energy conversion devices. It is still difficult to develop non-precious nanocatalysts for ORR that have high activity and increased durability for practical application. Herein, bimetallic FeMn(mIm)-N-C composite incorporated with Fe and Mn via an encapsulation-ligand exchange technique is prepared and established as an efficient ORR catalyst. The results reveal that FeMn(mIm)-N-C shows outstanding ORR performance with E_1/2 of 0.861 V and 0.778 V in alkaline and acid solutions, along with robust durability. Additionally, the assembled Zn-Air batteries (ZAB) and proton exchange membrane fuel cells (PEMFCs) both have exceptional power densities and show promise for long-term stability compared to 20% Pt/C. The present work provides a useful strategy for designing and synthesizing a reliable low-cost and high-efficient electrocatalysts for energy conversion and storage.

Molten salt-assisted synthesis of special open-cell Fe, N co-doped porous carbon as an efficient electrocatalyst for zinc–air batteries

Fe, N co-doped porous carbon (Fe–N–C) with open frame structure is prepared by molten salt-assisted pyrolysis strategy, which exhibits superior ORR performance and high specific capacity.

Efficient fish-scale CeO2/NiFeCo composite material as electrocatalyst for oxygen evolution reaction

An electrochemical catalyst with efficient, stable, inexpensive energy storage for oxygen evolution and hydrogen evolution has raised global concerns on energy, calling for high-performance materials for effective treatments. In this paper, novel amorphous polymetallic doped CeO₂particles were prepared for an electrochemical catalyst via homogeneous phase precipitation at room temperature. Metal ions can be easily embedded into the oxygen vacancies formed by CeO₂, and the the electron transport capacity of the CeO₂/NiFeCo electrocatalyst is improved owing to the increase in active sites. In addition, the amorphous CeO₂/NiFeCo composite material is in a metastable state and will transform into different active states in a reducing or oxidizing environment. Furthermore, the amorphous material drives oxygen evolution reaction (OER) through the lattice oxygen oxidation mechanism (LOM), while LOM can effectively bypass the adsorption of strongly related intermediates in the adsorbate release mechanism, thus promoting OER procedure in a timely manner. As a result, CeO₂/NiFeCo exhibits a lower oxygen evolution overpotential of 260 mV at 10 mA cm^-2current density, which shows a predatorily competitive advantage compared with commercially available RuO₂and the reported catalysts.

N-Doped porous biocarbon materials derived from soya peptone as efficient electrocatalysts for the ORR

A non-noble metal oxygen reduction catalyst was designed and fabricated via a facile carbonization of soya peptone and ZnCl₂.