Developing highly efficient single-atom catalysts (SAC) for oxygen reduction/evolution reactions (ORR/OER) shows great promise in rechargeable Zn-air batteries (RZABs). As one of the most appealing candidates for oxygen electrocatalysis, Fe-N-C catalysts are still suffered from the suboptimal adsorption of oxygen intermediates. Herein, a facile strategy to optimize the activity of Fe-based SAC is achieved through the construction of well-dispersed FeN4/CuN4 dual single-atom sites and FeCu atomic clusters on lignin-derived porous carbon nanosheets (Fe,Cu-DSAs/ACs) by engineering metal-lignin coordination complexes. The optimized catalyst demonstrates remarkable bifunctional ORR/OER activity with a low potential gap of 0.686 V, which is comparable to benchmark Pt/C+RuO2 and even superior to previously reported non-precious metal catalysts. When assembled in RZABs, it exhibits superior energy and power density, as well as excellent cycling stability up to 500 h. Theoretical calculations demonstrate that coexisting Cu-N4 sites and FeCu atomic clusters could collaboratively break the symmetric electronic structure of Fe-N4 and induce a downward shift in the d-band center, thus reducing the adsorption energy of oxygenated intermediates and promoting both the ORR and OER performance. This work proposes a universal and sustainable strategy for electron regulation of M-N-C, thereby offering key insights for the design of advanced multifunctional electrocatalysts for future energy applications.
Chen et al. (Mon,) studied this question.