CO ₂ ‐Mediated Hydrogen Energy Release‐Storage Enabled by High‐Dispersion Gold‐Palladium Alloy Nanodots

Abstract Developing and fabricating a heterogeneous catalyst for efficient formic acid (FA) dehydrogenation coupled with CO ₂ hydrogenation back to FA is a promising approach to constructing a complete CO ₂ ‐mediated hydrogen release‐storage system, which remains challenging. Herein, a facile two‐step strategy involving high‐temperature pyrolysis and wet chemical reduction processes can synthesize efficient pyridinic‐nitrogen‐modified carbon‐loaded gold‐palladium alloy nanodots (AuPd alloy NDs). These NDs exhibit a prominent electron synergistic effect between Au and Pd components and tunable alloy−support interactions. The pyridinic‐N dosage in carbon substrate improves the surface electron density of the alloy catalyst, thus regulating the chemical adsorption of FA molecules. Specifically, the engineered Au ₃ Pd ₇ /CN _0.25 demonstrates an outstanding room‐temperature FA dehydrogenation efficiency, achieving ≈100% conversion and an initial turnover frequency (TOF) of up to 9049 h ⁻¹ . The versatile AuPd alloy NDs also show the ability to convert CO ₂ , one of the products of FA dehydrogenation, into FA (formate) with a 90.8% yield under mild conditions. Moreover, in‐depth insights into the unique alloyed microstructure, structure‐activity relationship, key intermediates, and the alloy‐driven five‐step reaction mechanism involving the rate‐determining step of C─H bond cleavage from critical *HCOO species via D‐labeled isotope, in situ infrared spectroscopy, and theoretical calculations are investigated.