In a green energy economy, electrocatalysis is essential for chemical energy conversion and to produce value added chemicals from regenerative resources. To be widely applicable, an electrocatalyst should comprise the Earth's crust's most abundant elements. The most abundant 3d metal, iron, with its multiple accessible redox states has been manifold applied in chemocatalytic processes. However, due to the low conductivity of Fe^IIIO_xH_y phases, its applicability for targeted electrocatalytic oxidation reactions such as water oxidation is still limited. Herein, it is shown that iron incorporated in conductive intermetallic iron silicide (FeSi) can be employed to meet this challenge. In contrast to silicon‐poor iron–silicon alloys, intermetallic FeSi possesses an ordered structure with a peculiar bonding situation including covalent and ionic contributions together with conducting electrons. Using in situ X‐ray absorption and Raman spectroscopy, it could be demonstrated that, under the applied corrosive alkaline conditions, the FeSi partly forms a unique, oxidic iron(III) phase consisting of edge and corner sharing [FeO₆] octahedra together with oxidized silicon species. This phase is capable of driving the oxyge evolution reaction (OER) at high efficiency under ambient and industrially relevant conditions (500 mA cm⁻² at 1.50 ± 0.025 V_RHE and 65 °C) and to selectively oxygenate 5‐hydroxymethylfurfural (HMF).

The development of novel earth‐abundant metal‐based catalysts to accelerate the sluggish oxygen evolution reaction (OER) is crucial for the process of large‐scale production of green hydrogen. To solve this bottleneck, herein, a simple one‐pot colloidal approach is reported to yield crystalline intermetallic nickel silicide (Ni ₂ Si), which results in a promising precatalyst for anodic OER. Subsequently, an anodic‐coupled electrosynthesis for the selective oxidation of organic amines (as sacrificial proton donating agents) to value‐added organocyanides is established to boost the cathodic reaction. A partial transformation of the Ni ₂ Si intermetallic precatalyst generates a porous nickel(oxy)hydroxide phase modified with oxidic silicon species as unequivocally demonstrated by a combination of quasi in situ Raman and X‐ray absorption spectroscopy as well as ex situ methods. The activated form of the catalyst generates a geometric current density of 100 mA cm ⁻² at an overpotential (η ₁₀₀ ) of 348 mV displaying long‐term durability over a week and high efficiency in paired electrolysis.

The [FeFe]-hydrogenases of bacteria and algae are the most efficient hydrogen conversion catalysts in nature. Their active-site cofactor (H-cluster) comprises a [4Fe–4S] cluster linked to a unique diiron site that binds three carbon monoxide (CO) and two cyanide (CN⁻) ligands. Understanding microbial hydrogen conversion requires elucidation of the interplay of proton and electron transfer events at the H-cluster. We performed real-time spectroscopy on [FeFe]-hydrogenase protein films under controlled variation of atmospheric gas composition, sample pH, and reductant concentration. Attenuated total reflection Fourier-transform infrared spectroscopy was used to monitor shifts of the CO/CN⁻ vibrational bands in response to redox and protonation changes. Three different [FeFe]-hydrogenases and several protein and cofactor variants were compared, including element and isotopic exchange studies. A protonated equivalent (HoxH) of the oxidized state (Hox) was found, which preferentially accumulated at acidic pH and under reducing conditions. We show that the one-electron reduced state Hred′ represents an intrinsically protonated species. Interestingly, the formation of HoxH and Hred′ was independent of the established proton pathway to the diiron site. Quantum chemical calculations of the respective CO/CN⁻ infrared band patterns favored a cysteine ligand of the [4Fe–4S] cluster as the protonation site in HoxH and Hred′. We propose that proton-coupled electron transfer facilitates reduction of the [4Fe–4S] cluster and prevents premature formation of a hydride at the catalytic diiron site. Our findings imply that protonation events both at the [4Fe–4S] cluster and at the diiron site of the H-cluster are important in the hydrogen conversion reaction of [FeFe]-hydrogenases.