Template-Oriented Synthesis of Fe–N-Codoped Graphene Nanoshells Derived from Petroleum Pitch for Efficient Nitroaromatics Reduction

Engineering adjacent N, P and S active sites on hierarchical porous carbon nanoshells for superior oxygen reduction reaction and rechargeable Zn-air batteries

Heteroatom-doped carbon materials have been regarded as sustainable alternatives to the noble-metal catalysts for oxygen reduction reaction (ORR), while the catalytic performances still remain unsatisfactory. Herein, we develop a metal-free adjacent N, P and S-codoped hierarchical porous carbon nanoshells (NPS-HPCNs) through a novel layer-by-layer template coating method. The NPS-HPCNs is rationally fabricated by crosslinking of polyethyenemine (PEI) and phytic acid (PA) on nano-SiO₂ template surface and subsequently coating of viscous sulfur-bearing petroleum pitch, followed by pyrolysis and alkaline etching. Soft X-ray absorption near-edge spectroscopy (XANES) analysis and density functional theory (DFT) calculations prove the engineering of adjacent N, P and S atoms to generate synergistic and reinforced active sites for oxygen electrocatalysis. The NPS-HPCNs manifests excellent ORR activity with a half-wave potential (E_1/2) of 0.86 V, as well as promoted durability and methanol tolerance in alkaline medium. Remarkably, the NPS-HPCNs-based Zn-air battery delivers an open-circuit voltage of 1.479 V, a considerable peak power density of 206 mW cm^-2 and robust cycling stability (over 200 h), even exceeding the commercial Pt/C catalyst. This study offers fundamental insights into the construction and synergistic mechanism of adjacent heteroatoms on carbon substrate, providing advanced metal-free electrocatalysts for Zn-air batteries and other energy conversion and storage devices.

Intriguing hierarchical Co@NC microflowers in situ assembled by nanoneedles: Towards enhanced reduction of nitroaromatic compounds via interfacial synergistic catalysis

Developing highly efficient and cost-effective catalyst with tuned microstructure holds great promise in the reduction of nitroaromatic compounds under mild reaction conditions. Herein, we report a new Co@NC-MF catalyst with a fascinating hierarchical flower-like architecture in situ assembled from uniform Co@NC nanoneedles, which can function as a favorable platform for the efficient reduction of nitroaromatic compounds in the presence of NaBH₄. In addition with the structural advantage, the characterization and experimental results demonstrate the enormous advantage of interfacial synergistic catalysis in enhancing the catalytic performance. The outside electron-rich N-doped carbon layer as Lewis basic sites and the inside Co nanoparticles are responsible for the adsorption of 4-nitrophenol (4-NP) and generation of active hydrogen species, respectively. This work contributes to the construction of well-integrated composites with well-balanced interface synergy to boost the catalytic performance in various heterogeneous reactions.

Fe Single Atoms and Fe2O3 Clusters Liberated from N-Doped Polyhedral Carbon for Chemoselective Hydrogenation under Mild Conditions

In the area of catalysis, selective reduction of nitro compounds to amino compounds is a colossal challenge due to the existence of competitive reducible functional groups. Herein, an Fe-based catalyst Fe_SAs/Fe₂O_3ACs/N-doped polyhedral carbon (NPC) has been designed and synthesized. As we expected, compared with Fe_SAs and Fe_NPs, Fe_SAs/Fe₂O_3ACs/NPC shows excellent catalytic performance (turnover frequency up to 1923 h^-1, calculated with nitrobenzene), chemoselectivity, and tolerance during the hydrogenation reaction of nitro compounds under room temperature because of the synergistic effects between Fe_SAs and Fe₂O_3ACs. The theoretical calculations show that Fe_SAs prefers to undergo hydrazine decomposition to generate hydrogen and the Fe₂O_3ACs surface is more active toward the nitrobenzene reduction to aniline.