Formic Acid\nDehydrogenation over a Recyclable and\nSelf-Reconstructing Fe/Activated Carbon Catalyst

A novel catalyst, denoted as AC<sub>ox</sub>@ImFe, was\nsynthesized\nusing matrix-activated oxidized carbon (AC<sub>ox</sub>) featuring\na [Fe<sup>2+</sup>-imidazole]-based complex covalently bonded to the\ncarbon surface through Si–O–C bonding. The catalytic\nsystem, distinguished by its innovative hybrid structure that includes\nFe<sup>2+</sup> and imidazole on an oxidized carbon matrix in the\npresence of a polydentate phosphine, demonstrated remarkable turnover\nnumbers (TONs), reaching 428,880 and effectively decomposed 53 mL\nof formic acid (FA) over 8 cycles. This sustained performance underscores\nthe effectiveness, stability, and durability of the catalyst, which\nwas further evidenced by a cumulative H<sub>2</sub> production of\n22.1 L over the same period. Structural analysis using Raman, Fourier\ntransform infrared spectroscopy (FT-IR), scanning electron microscopy\n(SEM), and electron paramagnetic resonance (EPR) spectroscopy revealed\nstructural changes in the used catalyst compared to the pristine material.\nDespite the observed structural changes, such as Fe-site aggregation\nand matrix restructuring, the catalyst maintained a high efficiency,\nwith enhanced activity noted with each reuse. The stability of the\ncarbon-based radicals from the matrix was confirmed, which is crucial\nfor the sustained performance of the catalyst. Notably, upon repeated\nuse, the catalyst underwent a self-reconstruction process, which is\nlinked to alterations in the hydrophobicity of the catalyst and the\noverall structure, resulting in enhanced water durability and improved\nperformance, making AC<sub>ox</sub>@ImFe a robust and effective system\nfor sustainable H<sub>2</sub> production.