Scientists from Institute of Solid State Physics, Hefei Institutes of Physical Science (HFIPS) of Chinese Academy of Sciences (CAS) have synthesized an oxygen-coordinated Fe single atoms and atom clusters catalyst, manifesting superior electrocatalytic performance toward H₂O₂ production and biomass upgrading.

Hydrogen peroxide (H₂O₂) is a widely used chemical with applications in diverse fields such as environment, energy, and healthcare. While traditionally manufactured through energy-intensive processes, electrocatalytic synthesis offers a greener and more efficient method using water and oxygen. However, this approach requires advanced electrocatalysts for high yield and selective H₂O₂ production, and further attention is needed for utilizing the generated H₂O₂, particularly in electrochemical organic oxidation processes. This presents significant potential for value-added applications beyond environmental remediation.

In this study, the scientists utilized bacterial cellulose as the adsorption regulator and carbon source in combination with a multi-step approach involving wet-chemistry impregnation, pyrolysis, and acid-etching processes to create a catalyst termed FeSAs/ACs-BCC, consisting of oxygen-coordinated Fe single atoms and atom clusters. The presence of both Fe single atoms and clusters was confirmed using advanced imaging techniques such as aberration-corrected scanning transmission electron microscopy. Also, the atomic structure of Fe was determined using X-ray fine structure absorption spectroscopy and X-ray photoelectron spectroscopy.

This catalyst demonstrated outstanding electrocatalytic performance and selectivity for the 2-electron oxygen reduction reaction (2e^- ORR) under alkaline conditions. Further H-cell experiments confirmed the accumulation of H₂O₂ in the electrolyte.

Researchers successfully coupled the in situ generated H₂O₂ with the electro-Fenton process using ethylene glycol as the reactant and acidified 0.1M Na₂SO₄ as the electrolyte. This led to a high rate of ethylene glycol conversion and high selectivity for formic acid, showing that the electro-Fenton process has the potential to improve biomass-derived feedstocks through oxidative upgrading.

Aside from that, they developed a three-phase flow cell based on the gas diffusion electrode to further enhance the H₂O₂ yield.

Density functional theory analyses indicated that the actual catalytically active sites in the 2e^- ORR process were the Fe clusters, and the electronic interaction between Fe single atoms and Fe clusters could significantly enhance the electrocatalytic performance toward 2e^- ORR.

This work would be helpful for design and development of atomic level electrocatalysts for high-efficiency 2e^- ORR to H₂O₂ and biomass upgrading.

Fig. 1 Characterizations, electrochemical H₂O₂ synthesis performance and coupled electro-Fenton process of FeSAs/ACs-BCC. (Image by XU Hui)