Kinetically Facilitating Two-electron Oxygen Reduction by the Synergy of Multiple Pyrrolic Nitrogen Sites for Ultra-high-yield Electrochemical Hydrogen Peroxide Production

Abstract

Electrocatalytic hydrogen peroxide (H2O2) production via the two-electron oxygen reduction reaction (2e−-ORR) is a promising alternative to the energy-intensive and high-pollution anthraquinone oxidation process. However, developing advanced electrocatalysts with high H2O2 yield, selectivity, and durability is still challenging, because of the limited quantity and easy passivation of active sites on typical metal-containing catalysts, especially for the state-of-the-art single-atom ones. Addressing this, we herein report a synergy of multiple pyrrolic N sites located on a graphene/mesoporous carbon composite for high-rate and high-efficiency 2e−-ORR catalysis. The coordination of pyrrolic N sites effectively modulates the adsorption configuration of the *OOH species and reduces the reaction barrier for 2e−-ORR, thus providing a kinetically favorable pathway for H2O2 production, as demonstrated by a combined explicit solution model and slow-growth approach investigation. Consequently, a record-high H2O2 yield of up to 30 mol g−1 h−1 has been achieved on this material, together with a satisfactory Faradaic efficiency of 80% and excellent durability, yielding a high H2O2 concentration of 7.2 g L−1. This strategy of manipulating the adsorption configuration of reactants by the synergy of multiple non-metal active sites thus provides a highly efficient and durable metal-free electrocatalyst for 2e−-ORR with high practical feasibility.

Urea and ammonium fluoride di-nitrogen and Cu & Fe bi-metal co-doped carbon felt as cathode for electro-Fenton degradation of norfloxacin: 1O2-dominated oxidation pathway

“…4b, it can be seen that most of the doped N elements were in the form of pyrrole nitrogen (C-N). 56 Given that pyrrole nitrogen is only present at the defects and edges of the carbon substrate, 57 more pyrrole nitrogen indicated more active sites. The relative content of pyrrole nitrogen in C-CuFe/N was greater than that in C-CuFe/FN, suggesting that doping with double nitrogens was favourable for the generation of defects and active sites.…”

Selective oxygen reduction reaction: mechanism understanding, catalyst design and practical application

“…This is crucial for researchers to study and understand reaction mechanisms. 164 Just as in the aforementioned three studies, whether it is surface modication, development of edges as active sites, or utilization of single atoms to enhance two-electron selectivity, all of them cannot avoid the adjustment of the electronic structure to alter the strength of adsorption of oxygen and its reaction intermediates. [208][209][210][211] 5.1.3 Pore regulation strategy.…”

Fe, N-Doped Hollow Porous Carbon Spheres Decorated with Ultrasmall Co NPs as Efficient Bifunctional Electrocatalysts for Rechargeable Zinc–Air Batteries

“…10 Additionally, carbon-based materials modified by N atoms have also been widely investigated because N-doping favors improving the conductivity and wettability of electrode catalysts, and disperse metal NPs through the Co/Fe−Nx coupling. 11 The good hydrophilicity boosts fast transport of electrolyte during the ORR−OER process, thereby enhancing the electrocatalysis performance. Generally, a high-performance bifunctional catalyst for ORR/OER should possess several superiorities, i.e., (i) high specific surface area and hierarchical porous structure ensure the short diffusion distances of electrolyte and reactant to the catalytic active sites; (ii) uniform distribution of multicomponent active dopants, i.e., Fe, Co, N, etc., affords highly exposed active sites; (iii) the generation of numerous defects can contribute new catalytic active sites.…”