Enhanced oxygen reduction with single-atomic-site iron catalysts for a zinc-air battery and hydrogen-air fuel cell

Abstract

Efficient, durable and inexpensive electrocatalysts that accelerate sluggish oxygen reduction reaction kinetics and achieve high-performance are highly desirable. Here we develop a strategy to fabricate a catalyst comprised of single iron atomic sites supported on a nitrogen, phosphorus and sulfur co-doped hollow carbon polyhedron from a metal-organic framework@polymer composite. The polymer-based coating facilitates the construction of a hollow structure via the Kirkendall effect and electronic modulation of an active metal center by long-range interaction with sulfur and phosphorus. Benefiting from structure functionalities and electronic control of a single-atom iron active center, the catalyst shows a remarkable performance with enhanced kinetics and activity for oxygen reduction in both alkaline and acid media. Moreover, the catalyst shows promise for substitution of expensive platinum to drive the cathodic oxygen reduction reaction in zinc-air batteries and hydrogen-air fuel cells.

Engineering Local Coordination Environments of Atomically Dispersed and Heteroatom‐Coordinated Single Metal Site Electrocatalysts for Clean Energy‐Conversion

“…Yellow and blue areas represent charge accumulation and depletion, respectively. Reproduced with permission . Copyright 2018, Springer Nature.…”

“…g) Schematic illustration of preparation of Fe SACs supported on N, P, and S codoped hollow carbon and h) corresponding element mapping. Reproduced with permission . Copyright 2018, Nature Publishing Group.…”

“…Polymer or supramolecular composite precursors are usually more effective for forming stable carbonized substrates with high doping contents while maintaining uniform distribution of dopant atoms than small molecules due to their relatively high boiling points or decomposition temperatures. For example, Chen et al reported the fabrication of isolated FeN 4 sites supported on N, P, and S codoped hollow carbon polyhedrons from a S‐, P‐containing polymer coated MOFs precursor (Figure g,h) . Besides acting as S and P resources, the polymer coating can lead to a hollow structure via the Kirkendall effect.…”

“…However, the electronic modulation mechanisms remain controversial. The DFT calculations in many studies suggest that the reductive release of OH* (*OH + 3OH − + e − → 4OH − + *) should be the rate‐limiting step if the ORR pathway follows the associative mechanism because the adsorption of OH* intermediates on the Fe center is too strong . The expected role of S doping is therefore to weaken the OH* binding which improves ORR activity and kinetics.…”

Densely Populated Single Atom Catalysts

“…Electrochemical energy storage and conversion technology have been widely studied to produce sustainable and renewable energy . Many advanced clean energy technologies, such as fuel cells, metal air batteries, and water splitting, etc., require highly active catalysts to lower the energy barrier and increase the reaction rate with an efficient and stable route.…”