Bi-Doped Pd Aerogels with Tensile-Strain-Induced Cascade Orbital Hybridization Boost H 2 O 2 Selective Activation for Efficient Pesticide Distinction

The selective activation of H 2 O 2 into hydroxyl radicals (•OH) through the synergistic interplay between the nanozyme’s internal orbital interactions and external orbital coupling with intermediates presents an important scientific challenge. In this study, we demonstrate that PdBi aerogels with controllable tensile strain first enhance the Pd d orbital energy level through p–d orbital hybridization, and subsequently, the hybridized Pd d orbitals couple sequentially with the molecular orbitals of H 2 O 2 , forming a cascade of orbital hybridizations. High-performance liquid chromatography quantitative analysis reveals that the engineered PdBi aerogels remarkably improve •OH selectivity from 73.3% to 95.4%, importantly boosting both the activation efficiency and selectivity. Experimental studies and theoretical calculations have demonstrated that the hybridization of the d orbitals of Pd and the p orbitals of Bi in PdBi aerogels initially raises the d-band energy level of the Pd atoms. During the activation of H 2 O 2 , the high-energy 4d xz/yz and 4d z 2 orbitals of Pd further hybridize with the 2π* and 5σ orbitals of H 2 O 2 , thereby enhancing the orbital interaction with H 2 O 2 and creating optimal conditions for O–O bond cleavage and consequently enhancing the efficiency of •OH generation. Capitalizing on the differential reactivity patterns of various pesticides with PdBi aerogels, we develop a colorimetric sensor array for the discrimination and simultaneous detection of pesticide residues. Taking chlorpyrifos as an example, the detection limit is 0.23 μM, demonstrating good detection sensitivity. This work presents an orbital-level design strategy for creating highly selective nanozymes in H 2 O 2 activation systems.