Modulating Oxygen Reduction Behaviors on Nickel Single-Atom Catalysts to Probe the Electrochemiluminescence Mechanism at the Atomic Level

Luminol-dissolved O-2 electrochemiluminescence (ECL)-sensing platforms have been widely developed for sensitive and reliable detection, while their actual ECL mechanisms are still in controversy due to the involved multiple reactive oxygen species (ROS). Different from the structural complexity of nanomaterials, well-defined single-atom catalysts (SACs) as coreaction accelerators will provide great prospects for investigating the ECL mechanism at the atomic level. Herein, two carbon-supported nickel SACs with the active centers of Ni-N-4 (Ni-N-4/C) and Ni-N2O2 (Ni-N-2O2/C) were synthesized as efficient coreaction accelerators to enhance the ECL signals of a luminol-dissolved O-2 system. By modulating the surrounding environment of the center metal atoms, their corresponding oxygen reduction behaviors can be well controlled to selectively produce intermediate ROS, giving a great chance to study the following ECL process. According to the experimental and calculated results, the superoxide radical (O-2(center dot-)) acts as the main radical for the ECL reaction and the Ni-N-4/C catalyst with the four-electron pathway to activate dissolved O-2 is preferential to enhance ECL emission.

Automated summary

This study demonstrates the potential application of carbon-supported nickel SACs as coreaction accelerators in enhancing ECL signals; By modulating the surrounding environment of the center metal atoms, control over oxygen reduction behaviors to selectively produce intermediate ROS provides an important opportunity for studying the ECL process; Experimental and calculated results suggest that the superoxide radical (O-2(center dot-)) is the main radical for the ECL reaction, with the Ni-N-4/C catalyst preferred for its four-electron pathway to activate dissolved O-2 and enhance ECL emission.