Efficient Oxygen Reduction Research Articles

Transition metals anchored on nitrogen-doped graphdiyne for an efficient oxygen reduction reaction: a DFT study.

The search for highly active and low-cost single-atom catalysts for the oxygen reduction reaction (ORR) is essential for the widespread application of proton exchange membrane fuel cells. Transition metals anchored on nitrogen-doped graphdiyne (GDY) have attracted considerable interest as potentially excellent catalysts for the ORR. However, the relationship between the active site and nitrogen-doped GDY remains unclear. In this work, we conducted a systematic investigation of sp-hybridized N atoms anchoring single transition metal atoms of 3d and 4d on GDY (TMC2N2) as electrocatalysts for the ORR. Firstly, 18 kinds of TMC2N2 were determined to have good thermodynamic stability. Due to the extremely strong adsorption of *OH, TMC2N2 exhibits inferior ORR performance compared to traditional Pt(111). Considering that *OH adsorption hinders the catalytic activity of TMC2N2, we modified the OH ligand of TMC2N2 to develop the high-valent metal complex (TMC2N2-OH) aiming to enhance the electrocatalytic activity. The adsorption of intermediates on most TMC2N2-OH is weakened after the modification of the OH ligand, especially for the adsorption of *OH. Thus, by comparing the ORR overpotential of catalysts before and after ligand modification, we find that the catalytic activity of different TMC2N2-OHs improves to various degrees. MnC2N2-OH, TMC2N2-OH, and TcC2N2-OH exhibit relatively high ORR catalytic activity, with overpotentials of 0.93 V, 1.19 V, and 0.92 V, respectively. Furthermore, we investigated the cause of improved catalytic activity of TMC2N2-OH and found that the modified coordination environment of the catalyst led to adjusted adsorption of ORR intermediates. In summary, our work sheds light on the relationship between nitrogen-doped GDY and transition metal sites, thus contributing to the development of more efficient catalysts.

Integrating multiple regulatory strategies: phase, morphology and interface engineering to construct a hierarchical Ni2P–MoS2/rGO heterostructure catalyst for efficient oxygen reduction reaction

Two-dimensional (2D) molybdenum disulfide (MoS2) with a large surface area and unique electronic properties has emerged as a promising noble metal-free catalyst for electrochemical energy storage/conversion applications.

Boosting the oxygen reduction activity of non-metallic catalysts via geometric and electronic engineering through nitrogen and chlorine dual-doping.

The development of heteroatom dual-doped porous carbon frameworks with uniform doping is highly desirable for achieving highly efficient oxygen reduction reaction (ORR) activity, due to their tunable chemical and electronic structures. Herein, porous covalent triazine-based frameworks (CTFs) incorporating nitrogen/chorine dual-doped porous carbon networks were fabricated by selecting 1,3-bis(4-cyanophenyl) imidazolium chloride as a building block, in a facile and controllable way via a bottom-up strategy. The resulting nitrogen/chorine dual-doped catalyst CCTF-700 exhibits excellent ORR performance with a more positive onset and half-wave potential (0.85 V vs. RHE), higher diffusion-limited current density and significantly improved stability in comparison with the benchmark commercial 20 wt% Pt/C catalyst. It is worth mentioning that CCTF-700 shows one of the best ORR performances among all the reported metal-free electrocatalysts under alkaline conditions. This work paves the way for a controllable and reliable strategy to craft highly efficient heteroatom dual-doped carbon catalysts for energy conversion.

Ordered mesoporous carbon with binary CoFe atomic species for highly efficient oxygen reduction electrocatalysis.

The exploration of powerful, efficient and precious metal-free electrocatalysts for facilitating the sluggish kinetics of the oxygen reduction reaction (ORR) is a crucial endeavor in the development and application of energy conversion and storage devices. Herein, we have rationally designed and synthesized bimetallic CoFe species consisting of CoFe nanoparticles and atomically dispersed dual atoms anchored on an ordered mesoporous carbon matrix (CoFe/NC) as highly efficient ORR electrocatalysts. The pyrolyzation temperature for CoFe/NC plays a vital role in regulating the morphology and composition of both the carbon matrix and CoFe species. The optimized CoFe/NC-750 exhibits a favorable ORR performance in 0.1 M KOH with a high half-wave potential (E1/2) of 0.87 V vs. RHE, excellent tolerance to methanol and remarkable durability (no obvious decrease in E1/2 value after 3000 cycles), all of which are superior to the performance of commercial Pt/C. Experimental measurements and density functional theory (DFT) calculations reveal that the improved ORR performance of CoFe/NC-750 is mainly attributed to the electronic structure of atomically dispersed Fe active sites modulated by the surrounding CoFe alloys and Co single atoms, which accelerates the dissociation and reduction of intermediate OH* species and promotes the ORR process.

A single-atom iron catalyst on hierarchical N-doped carbon for highly efficient oxygen reduction in Zn–air batteries

Single-atom iron electrocatalysts have emerged as up-and-coming alternatives to platinum-based catalysts for the oxygen reduction reaction.

Topotactic N-doped carbon for efficient oxygen reduction reaction

A topotactic molecular doping strategy is developed via in situ coupling of dechlorinated carbon with ringed heterocyclic molecules under mild conditions.

Donor–acceptor iron phthalocyanine-based hyper-crosslinked polymers with a modulated electronic structure for efficient oxygen reduction reaction in aluminum–air batteries

Poly-FePc-based HCPs with TTF modification are constructed and applied as ORR catalyst for Al–air batteries. The donor–acceptor structure was incorporated into poly-FePc-HCP to achieve structural and electronic regulation.

Synthetic design of active and stable bimetallic PtTi nanoparticle electrocatalysts for efficient oxygen reduction at fuel cell cathodes

We explore and utilize correlations between wet-chemical synthesis parameters and the resulting atomic geometry and crystal phase structure of carbon-supported bimetallic PtTi/C alloy nanoparticles with excellent electrocatalytic reactivity for and...

Bioinspired molecular catalysts with a unique tricopper architecture for highly efficient oxygen reduction reaction.

In situ growth of intertwined trinuclear copper complexes (nCu3) on a cellulose-derived carbon support (CMC) produced a high-performance electrocatalyst (CMC-nCu3) for the oxygen reduction reaction (ORR), which demonstrated superior performance in zinc-air batteries compared to a commercial Pt/C catalyst. This work highlights the importance of copper-based molecular catalysts with rich and intertwined tricopper structures for boosting both ORR activity and stability.

Porphyrin-containing conjugated microporous polymers with gradient asymmetric design for efficient oxygen reduction

Gradient asymmetry is employed to design metal-free polymer electrocatalysts. The superior activity of the highly asymmetric PPA-BN is attributed to the abundant active sites and adequate oxygen intermediate adsorption by local charge distribution.

A potential well effect for efficient oxygen reduction and corrosion resistance under the operating temperature conditions of PEMFCs

F-doping forms an oxygen molecule potential well, altering the energy distribution function of oxygen. Thus, this effect induces a localized enrichment zone for oxygen, leading to enhanced O2 adsorption.

A ZIF-derived hollow carbon nanoframework loaded with FeCu alloy nanoparticles for efficient oxygen reduction reaction and zinc–air batteries

Superior performance over Pt catalysts in oxygen reduction achieved by loading FeCu alloy nanoparticles through hollow carbon shells constructed from MOF materials.

In situ self-assembly of molybdenum carbide and iron carbide heterostructures on N-doped carbon for an efficient oxygen reduction reaction.

Identifying highly stable, cost-effective, platinum-free, and efficient electrocatalysts for the oxygen reduction reaction (ORR) remains a formidable challenge. The ORR is important for advancing fuel cell and zinc-air battery (ZAB) technologies towards cost-efficiency and environmental sustainability. This work presents the utilization of economically viable materials through a straightforward synthesis process, exhibiting the development of efficient Mo2C/Fe3C-NC catalysts ingeniously derived from phosphomolybdic acid (PMA) and iron phthalocyanine (FePc). The results demonstrate that the optimized Mo2C/Fe3C-NC3 catalysts exhibit remarkable electrochemical performance, evidenced by an impressive onset potential of ∼1.0 V versus RHE, a half-wave potential of 0.89 V, and a superior current density of about 6.2 mA cm-2. As for their performance in ZABs, the optimized catalysts reach a peak power density of 142 mW cm-2 at a current density of 200 mA cm-2. This synergy, coupled with the uniform distribution of Mo2C and Fe3C nanoparticles, greatly enhances the active catalytic sites and promotes electrolyte diffusion. Our approach diverges from traditional methods by employing an in situ self-assembled heterostructure of Mo2C/Fe3C on nitrogen-doped carbon tubes, avoiding the conventional high-temperature hydrogen gas reduction process. Beyond serving as feasible alternatives to commercially available Pt/C catalysts, these materials hold promise for large-scale production owing to their affordability and the simplicity of the synthesis technique. Such a breakthrough paves the way towards the realization of sustainable energy technologies and lays the groundwork for further exploration into amplifying the scalability and efficiency of ORR catalysts.

Axial oxygen-bridged FeN4O/NC produced by ultrafast joule heating for efficient oxygen reduction reaction

Herein, we report an atomically dispersed Fe-N-C catalyst with axial oxygen ligands (FeN4O/NC) firstly synthesized by ultrafast joule heating. The formation of oxygen species between FeN4 and graphene, which offers...

Carboxylate trapping engineering to fabricate monodispersed dual-atom iron sites for efficient oxygen reduction

Atomically dispersed catalysts with dense accessible Fe–Fe binary active sites supported on hierarchically ordered porous N-doped carbon are prepared via a general carboxylate-assisted strategy and they display drastically enhanced ORR activity.

Electronic structure modification of metal phthalocyanines by a carbon nanotube support for efficient oxygen reduction to hydrogen peroxide.

An active and selective two-electron oxygen reduction reaction (2e- ORR) is required for efficient electrosynthesis of H2O2. This reaction can be promoted by metal phthalocyanines (MPcs), which serve as model catalysts with well-defined structures. MPc molecules have mostly been evaluated on conductive carbon-based substrates, including glassy carbon (GC) and carbon nanotubes (CNTs), yet their influence on the electrocatalytic properties is not well understood. This study demonstrated that the ORR activity per surface area was improved by up to 4-fold with MPc molecules supported on CNTs (MPc/CNTs, M = Co, Mn, and Fe) compared to MPc loaded directly on GC. Ultraviolet photoelectron spectroscopy and density functional theory calculations revealed that the CNTs modified the electronic structure of the MPc molecules to optimize the *OOH binding energy and boost the heterogeneous electron transfer rates. Detailed kinetic analysis enabled multiple reaction pathways to be decoupled to extract the metal-dependent intrinsic 2e-/4e- ORR activities. Finally, MPc/CNT catalysts were employed in an H2O2 electrosynthesis flow cell, which delivered an industrial-scale current density of -200 mA cm-2 and an H2O2 faradaic efficiency of 88.7 ± 0.6% with the CoPc/CNT catalyst in a neutral electrolyte.

P-Block metal atom-induced spin state transition of Fe-N-C catalysts for efficient oxygen reduction.

A deep understanding of the role of spin configurations of Fe-N-C catalysts in the adsorption and desorption of oxygen intermediates during ORRs is critical for the development of new catalysts for the ORR. Herein, we successfully implanted p-block metal single sites (SnN4, SbN4) into the Fe-N-C system to vary the spin states of Fe species and investigated the ORR performance of active metal centers with varying effective magnetic moments. Through a combination of zero-field cooling (ZFC) temperature-dependent magnetic susceptibility measurements and DFT calculations, we successfully established correlations between the spin state and ORR activity. Magnetic analysis reveals that the p-block metal catalytic sites can effectively induce a low-to-high (or medium) spin state transition of Fe centers. Consequently, the 3d orbital electrons in Fe,M-N-C catalysts penetrate the antibonding π-orbitals of oxygen more easily, thus optimizing the adsorption/desorption of key oxygen intermediates on Fe-N-C catalysts. As a result, the optimized Fe,M-N-C catalyst exhibits a half-wave potential of 0.97 V in a 0.1 M KOH electrolyte, as well as higher durability than conventional Pt/C catalysts. Moreover, the Fe,M-N-C catalysts show encouraging performance in a rechargeable Zn-air battery with high power density and long-term cyclability, indicating the practical applicability of these Fe,M-N-C catalysts.

Flexible Pt2Pd alloy nanosheet electrocatalysts for efficient oxygen reduction reaction and zinc–air batteries

A 2D Pt2Pd porous alloy nanosheet is synthesized through molten-alkali mechanochemical and borane morpholine complex reduction methods, which serves as an efficient catalyst for the oxygen reduction reaction.

N-doped WO3 anchored on porous carbon as boosted oxygen reduction catalyst for zinc-air batteries.

N-doped WO3 anchored on porous carbon (N-WO3/PNC) was synthesized as an efficient oxygen reduction catalyst. The N doping reduced the overpotential of WO3 during oxygen reduction. N-WO3/PNC displayed a half-wave potential of 0.85 V. An N-WO3/PNC-based zinc-air battery displayed a high power density of 209.7 mW cm-2.

Metal-chelating-membrane-derived TM/TMOx nitrogen-doped carbon fibers as efficient oxygen reduction electrocatalysts.

A metal-chelating membrane was exploited for the facile synthesis of N-doped graphitic carbon fibers (N-CFs) with abundant TM/TMOx nanoparticles completely exposed on the surfaces of the fibers. The ready accessiblity to multiple active sites and strong synergistic effects endowed the Fe/Fe3O4@N-CFs with optimal qualities, in particular delivering enhanced ORR performance in alkaline and neutral medium.