Atomically dispersed Fe-O4-C sites as efficient electrocatalysts for electrosynthesis of hydrogen peroxide

A zinc hydroxide-organic framework for electrochemical synthesis of H2O2

Zinc hydroxide-organic framework (Zn-HOF) nanosheets were synthesized by electrochemically triggered self-reconstruction of a double-ligand metal-organic framework (MOF) for the first time. This Zn-HOF catalyst exhibits high activity and selectivity towards the two-electron oxygen reduction reaction (2e-ORR), delivering a high H2O2 productivity of 3.95 mol gcat-1 h-1 at 0 V vs. RHE with a Faraday efficiency (FE) of approximately 96% in an alkaline electrolyte.

The steric hindrance effect of Co porphyrins promoting two-electron oxygen reduction reaction selectivity

A new Co 5,10,15,20-tetrakis(2',6'-dipivaloyloxyphenyl)porphyrin (1) with eight ester groups in all ortho and ortho' positions of phenyl groups was designed, which displayed significantly improved 2e oxygen reduction reaction (ORR) selectivity compared with a 5,10,15,20-tetrakis(para-dipivaloyloxyphenyl) porphyrin (2) without large steric groups. This work is significant to reveal the steric hindrance effect of metal porphyrins on electrocatalytic ORR selectivity.

Synthesis of Hydrogen Peroxide in Neutral Media by an Iron-Doped Nickel Phosphide Catalyst

The two-electron oxygen reduction reaction (2e- ORR) for electrochemical hydrogen peroxide (H2O2) synthesis has drawn much attention due to its eco-friendly, cost-effective, and highly efficient properties. Developing catalysts with excellent H2O2 production rates and selectivity is still a big challenge. In this work, an iron-doped nickel phosphide (Fe-Ni-P) catalyst was synthesized by a solvent thermal method. The synthesis temperature of 180 °C could obtain the best 2e- ORR catalyst, i.e., Fe-Ni-P-180, since the crystallization of metal phosphide under this temperature was promoted. In addition, Fe-Ni-P-180 had a high catalytic activity, high electron transfer rate, and low electrochemical resistance. The H2O2 production rate constant of Fe-Ni-P-180 was 9.99 ± 0.63 μM/(min cm2) and the Faradaic efficiency was 94.38 ± 4.68% at 0.25 V vs RHE, which increased by 57.9 and 15.4% compared with Ni-P, respectively. Fe-Ni-P-180 could work in a wide pH range of 5-9 with the optimized pH of 7, and it exhibited low specific energy consumption and great reusability. The elemental state analysis demonstrated that Niδ+, Feδ+, and Pδ- are all active species, and the doping of Fe increases the crystallization of metal phosphide.

Boosting sodium-ion batteries performance by N-doped carbon spheres featuring porous and hollow structures

Carbon materials are considered among the most promosing candidates for sodium ion batteries because of their competitive performance. Nevertheless, they suffer from low initial coulombic efficiencies (ICEs) and limited electrochemical performance. Herein, nitrogen-doped hollow carbon spheres (NHCSs) with a distinct porous structure are developed by a template-assisted carbonization of dopamine, followed by a template removal procedure. This advanced structural design, coupled with the surface chemistry of carbonized polydopamine, leads to an impressive ICE of 89.18% and a reversible capacity stabilized at ∼700 mA h g-1 at 50 mA g-1 after 100 cycles. Compared to commercial hard carbon anodes, NHCSs demonstrate superior rate performance, delivering a capacity of ∼200 mA g h-1 at 5 A g-1 with minimal capacity fading of ∼0.057 mA h g-1 per cycle over 1000 cycles. These findings highlight the potential of NHCSs as a high-performance anode material for sodium-ion batteries, offering both high efficiency and excellent cycling stability.

Single-Atom Co─O4 Sites Embedded in a Defective-Rich Porous Carbon Layer for Efficient H2O2 Electrosynthesis

The production of hydrogen peroxide (H2O2) via the two-electron electrochemical oxygen reduction reaction (2e- ORR) is an essential alteration in the current anthraquinone-based method. Herein, a single-atom Co─O4 electrocatalyst is embedded in a defective and porous graphene-like carbon layer (Co─O4@PC). The Co─O4@PC electrocatalyst shows promising potential in H2O2 electrosynthesis via 2e- ORR, providing a high H2O2 selectivity of 98.8% at 0.6 V and a low onset potential of 0.73 V for generating H2O2. In situ surface-sensitive attenuated total reflection Fourier transform infrared spectra and density functional theory calculations reveal that the electronic and geometric modification of Co─O4 induced by defective carbon sites result in decreased d-band center of Co atoms, providing the optimum adsorption energies of OOH* intermediate. The H-cell and flow cell assembled using Co─O4@PC as the cathode present long-term stability and high efficiency for H2O2 production. Particularly, a high H2O2 production rate of 0.25 mol g-1 cat h-1 at 0.6 V can be obtained by the flow cell. The in situ-generated H2O2 can promote the degradation of rhodamine B and sterilize Staphylococcus aureus via the Fenton process. This work can pave the way for the efficient production of H2O2 by using Co─O4 single atom electrocatalyst and unveil the electrocatalytic mechanism.