Highly Efficient Au1Pd Single-Atom Alloy Catalyzing Reversible Formate/Bicarbonate Interconversion: Proof-of-Concept for Formate-Salt Cavern Hydrogen Storage.

Reversible hydrogen storage via formate/bicarbonate cycles is a promising strategy for large-scale hydrogen storage, while the lack of highly efficient catalysts for reversible interconversion remains a critical bottleneck. Herein, we report an amine-modified activated carbon-supported Au1Pd single-atom alloy (SAA) catalyst (Au1Pd20/AC-NH) as the key breakthrough to address this challenge, and further demonstrate its proof-of-concept application in a novel "Formate-Salt Cavern Hydrogen Storage System". Featuring atomically dispersed Au promoters anchored on Pd nanoparticles, Au1Pd20/AC-NH boosts Pd's intrinsic activity remarkably. Under near-ambient conditions, it exhibits exceptional turnover frequencies (TOFs, based on total active metal) of 4568 h-1 for dehydrogenation (80°C, 1 bar, 1 M HCOOK) and 77 h-1 for hydrogenation (30°C, 1 bar, 1.5 M KHCO3). Specifically, in the formate dehydrogenation reaction, the Au1Pd20/AC-NH catalyst exhibits a 45% higher initial TOF value at a conversion of 20% compared with monometallic Pd/AC-NH; meanwhile, its hydrogenation activity is increased by 34%. These values are among the highest reported under similar reaction conditions. Mechanistic analysis reveals that the superior catalytic performance stems from the Au1Pd SAA effect and synergistic interaction with surface ─NH─ groups, which collectively facilitate H2 dissociation and reactant adsorption. By establishing an efficient catalytic strategy and providing critical proof-of-concept, this work paves a viable pathway for large-scale hydrogen storage.