The oxygen reduction reaction (ORR) is a key cathodic process in clean energy-conversion devices, including fuel cells and metal–air batteries. However, its sluggish reaction kinetics severely limit the energy-conversion efficiency and practical application of these devices.
Fe–N–C single-atom catalysts, featuring high atomic utilization efficiency and tunable local electronic structures, are regarded as one of the most promising alternatives to noble-metal Pt-based catalysts. Nevertheless, conventional FeN 4 active sites still suffer from insufficient O 2 adsorption and activation capabilities, as well as unfavorable adsorption strengths toward ORR intermediates. Because the electronic structure and spin state of the Fe center directly affect its interaction with oxygen species, regulating the spin state of Fe sites to optimize O 2 adsorption and activation is expected to further improve the ORR performance of Fe–N–C catalysts.
The authors developed an FeCu dual-single-atom catalyst (FeCu–NC) featuring spatially adjacent FeN 4 and CuN 4 sites. In this catalyst, neighboring Cu atoms regulate the spin state of the Fe single-atom active centers and optimize the adsorption behavior of key ORR intermediates, thereby significantly enhancing the ORR activity.
Structural characterization revealed that both Fe and Cu were atomically dispersed and formed spatially adjacent Fe–N 4 and Cu–N 4 coordination structures, respectively. This well-defined configuration provides a clear structural model for investigating the regulatory effects of neighboring atoms on Fe active centers. Experimental results and theoretical calculations further demonstrated that the adjacent Cu sites enhanced spin polarization at the Fe sites and induced electronic-structure rearrangement. Consequently, the interaction between the Fe sites and O 2 was strengthened, facilitating O 2 adsorption and initial activation and accelerating the ORR kinetics.
Benefiting from its unique dual-single-atom-site configuration, FeCu–NC exhibited excellent ORR catalytic performance, with a half-wave potential of 0.88 V versus the reversible hydrogen electrode (RHE). In zinc–air battery tests, FeCu–NC also delivered superior discharge performance compared with a commercial Pt/C catalyst.
This study elucidates the intrinsic relationship between the regulation of the spin state of active centers by adjacent single-atom sites and oxygen activation behavior. It provides new insights into the design of highly efficient single-atom ORR catalysts through spin engineering.
Science China Chemistry
Experimental study