ZIF-8 derived nitrogen, phosphorus and sulfur tri-doped mesoporous carbon for boosting electrocatalysis to oxygen reduction in universal pH range

Earthworm-Inspired Co/Co3O4/CoF2@NSC Nanofibrous Electrocatalyst with Confined Channels for Enhanced ORR/OER Performance

The rational construction of highly active and durable oxygen-reactive electrocatalysts for oxygen reduction/evolution reaction (ORR/OER) plays a critical role in rechargeable metal-air batteries. It is pivotal to achieve optimal utilization of electrocatalytically active sites and valid control of the high specific internal surface area. Inspiration for designing electrocatalysts can come from nature, as it is full of precisely manipulated and highly efficient structures. Herein, inspired by earthworms fertilizing soil, a 3D carbon nanofibrous electrocatalyst with multiple interconnected nanoconfined channels, cobalt-based heterojunction active particles and enriched N, S heteroatoms (Co/Co3O4/CoF2@NSC with confined channels) is rationally designed, showing superior bifunctional electrocatalytic activity in alkaline electrolyte, even outperforming that of benchmark Pt/C-RuO2 catalyst. This work demonstrates a new method for porous structural regulation, in which the internal confined channels within the nanofibers are controllably formed by the spontaneous migration of cobalt-based nanoparticles under a CO2 atmosphere. Theoretical analysis reveals that constructing Co/Co3O4/CoF2@NSC electrocatalyst with confined channels can greatly adjust the electron distribution, effectively lower the reaction barrier of inter-mediate and reduce the OER/ORR overpotential. This work introduces a novel and nature-inspired strategy for designing efficient bifunctional electrocatalysts with well-designed architectures.

Ternary Heteroatomic Doping Induced Microenvironment Engineering of Low Fe-N4-Loaded Carbon Nanofibers for Bifunctional Oxygen Electrocatalysis

Fabricating highly efficient and long-life redox bifunctional electrocatalysts is vital for oxygen-related renewable energy devices. To boost the bifunctional catalytic activity of Fe-N-C single-atom catalysts, it is imperative to fine-tune the coordination microenvironment of the Fe sites to optimize the adsorption/desorption energies of intermediates during oxygen reduction/evolution reactions (ORR/OER) and simultaneously avoid the aggregation of atomically dispersed metal sites. Herein, a strategy is developed for fabricating a free-standing electrocatalyst with atomically dispersed Fe sites (≈0.89 wt.%) supported on N, F, and S ternary-doped hollow carbon nanofibers (FeN4 -NFS-CNF). Both experimental and theoretical findings suggest that the incorporation of ternary heteroatoms modifies the charge distribution of Fe active centers and enhances defect density, thereby optimizing the bifunctional catalytic activities. The efficient regulation isolated Fe centers come from the dual confinement of zeolitic imidazole framework-8 (ZIF-8) and polymerized ionic liquid (PIL), while the precise formation of distinct hierarchical three-dimensional porous structure maximizes the exposure of low-doping Fe active sites and enriched heteroatoms. FeN4 -NFS-CNF achieves remarkable electrocatalytic activity with a high ORR half-wave potential (0.90 V) and a low OER overpotential (270 mV) in alkaline electrolyte, revealing the benefit of optimizing the microenvironment of low-doping iron single atoms in directing bifunctional catalytic activity.

Carbon-Based Electrocatalysts for Acidic Oxygen Reduction Reaction

Oxygen reduction reaction (ORR) is vital for clean and renewable energy technologies, which require no fossil fuel but catalysts. Platinum (Pt) is the best-known catalyst for ORR. However, its high cost and scarcity have severely hindered renewable energy devices (e.g., fuel cells) for large-scale applications. Recent breakthroughs in carbon-based metal-free electrochemical catalysts (C-MFECs) show great potential for earth-abundant carbon materials as low-cost metal-free electrocatalysts towards ORR in acidic media. This article provides a focused, but critical review on C-MFECs for ORR in acidic media with an emphasis on advances in the structure design and synthesis, fundamental understanding of the structure-property relationship and electrocatalytic mechanisms, and their applications in proton exchange membrane fuel cells. Current challenges and future perspectives in this emerging field are also discussed.

In-situ fabrication of cobalt sulfide decorated N, S co-doped mesoporous carbon and its application as electrocatalyst for efficient oxygen reduction reaction

Designing an efficient electrocatalyst for facile oxygen reduction reaction (ORR) is essential to achieve higher fuel cell performance. Herein, we demonstrate the simple in-situ process to synthesize cobalt sulfide decorated...

Metal-free N and O Co-doped carbon directly derived from bicrystal Zn-based zeolite-like metal-organic frameworks as durable high-performance pH-universal oxygen reduction reaction catalyst

A simple and green approach is studied for the preparation of a high-activity metal-free N,O-codoped porous carbon (NOPC) electrocatalyst by one-step pyrolysis of pristine zinc-based zeolite-like metal-organic framework (Zn-ZMOF) synthesized by hydrothermal method from Zn²⁺and 4,5-imidazoledicarboxylic acid (H₃IDC) in H₂O solvent. It is found that the structure and electroactivity of Zn-ZMOF and NOPC vary with the molar ratio of H₃IDC to zinc acetate. NOPC shows pH-universal electrocatalytic property for oxygen reduction reaction and its electrocatalytic performance is similar to that of Pt/C in alkaline and neutral electrolytes, and is close to that of Pt/C in acidic electrolyte, which is a relatively rare case for metal-free porous carbon derived from pristine MOF. Meanwhile, NOPC displays higher long-term stability and better tolerance to methanol and carbon monoxide poisoning than that of commercial Pt/C. The excellent performance of NOPC is mainly due to the special structure of the precursor Zn-ZMOF, and the synergism of abundant active sites, micro/mesoporous structure, large specific surface area, and high degree of graphitization.

Zeolitic imidazolate frameworks as intrinsic light harvesting and charge separation materials for photocatalysis

Zeolitic imidazolate frameworks (ZIFs) are a subclass of metal organic frameworks that have attracted considerable attention in the past years and have found many applications including heterogeneous catalysis due to their highly ordered porous structure, large surface area, and structural flexibility. However, ZIFs are largely utilized as simple hosts or passive media for dispersing other catalytically active species, resembling the roles of zeolites in catalysis. In contrast, our recent findings show that ZIFs not only have broad absorption across the UV-visible and near IR spectral region but also have an exceptionally long-lived excited charge separated state, suggesting that ZIFs may be used as intrinsic light harvesting and photocatalytic materials rather than as inert hosts. This Perspective will focus on the recent progress on the fundamental studies of the intrinsic light absorption, charge separation, and photocatalytic properties of ZIFs and will discuss the outlook for future development.

A non-traditional biomass-derived N, P, and S ternary self-doped 3D multichannel carbon ORR electrocatalyst

A synthetic non-traditional biomass-derived ORR catalyst is developed to overcome traditional shortcomings, that is, the existence of solid micron blocks and fewer heteroatoms.