Orbital Coupling of Dual-Atom Sites Boosts Electrocatalytic NO Oxidation and Dynamic Intracellular Response

In situ measurement of nitric oxide (NO) in living tissue and single cells is highly important for achieving a profound comprehension of cellular functionalities and facilitating the precise diagnosis of critical diseases; however, the progress is greatly hindered by the weak affinity of ultratrace concentration NO in cellular environment toward electrocatalysts. Herein, a new strategy is reported for precisely constructing orbital coupled dual-atomic sites to enhance the affinity between the metal atomic sites and NO on a class of N-doped hollow carbon matrix dual-atomic sites Co─Ni (Co₁Ni₁-NC) for greatly boosting electrocatalytic NO performance. The as-synthesized Co₁Ni₁-NC demonstrates a substantially higher current density than Ni₁-NC and Co₁-NC, coupled with exceptional stability with a negligible degradation rate of 0.6 µA·cm^-2·h^-1, which is the best among the state-of-the-art electrocatalysts for NO oxidation. Experimental and theoretical investigations collectively reveal that the pivotal role of d-d orbit coupling between Co and Ni sites enables Ni to acquire additional electrons, leading to the occupation of Ni's 3d_xy/yz within the 2π orbitals of NO, thus weakening the N≡O triple bond and concurrently accelerating NO adsorption kinetics. It is demonstrated that Co₁Ni₁-NC-coated nanoelectrode can achieve the in situ sensing of NO in living organs and single cells.