The electrochemical reduction of nitrate (NO₃^-) and nitrite (NO₂^-) enables sustainable, carbon-neutral, and decentralized routes to produce ammonia (NH₃). Copper-based materials are promising electrocatalysts for NO_x^- conversion to NH₃. However, the underlying reaction mechanisms and the role of different Cu species during the catalytic process are still poorly understood. Herein, by combining quasi in situ X-ray photoelectron spectroscopy (XPS) and operando X-ray absorption spectroscopy (XAS), we unveiled that Cu is mostly in metallic form during the highly selective reduction of NO₃^-/NO₂^- to NH₃. On the contrary, Cu(I) species are predominant in a potential region where the two-electron reduction of NO₃^- to NO₂^- is the major reaction. Electrokinetic analysis and in situ Raman spectroscopy was also used to propose possible steps and intermediates leading to NO₂^- and NH₃, respectively. This work establishes a correlation between the catalytic performance and the dynamic changes of the chemical state of Cu, and provides crucial mechanistic insights into the pathways for NO₃^-/NO₂^- electrocatalytic reduction.

The effect of a local proton source on the activity of a bromotricarbonyl Mn redox catalyst for CO₂ reduction has been investigated. The electrochemical behaviour of the novel complex [fac-Mn(dhbpy)(CO)₃Br] (dhbpy = 4-phenyl-6-(1,3-dihydroxybenzen-2-yl) 2,2′-bipyridine), containing two acidic OH groups in the proximity of the metal centre, under a CO₂ atmosphere showed a sustained catalysis in homogeneous solution even in the absence of Brønsted acids.

We report here the first purely organometallic fac‐[Mn^I(CO)₃(bis‐^MeNHC)Br] complex with unprecedented activity for the selective electrocatalytic reduction of CO₂ to CO, exceeding 100 turnovers with excellent faradaic yields (η_CO≈95 %) in anhydrous CH₃CN. Under the same conditions, a maximum turnover frequency (TOF_max) of 2100 s⁻¹ was measured by cyclic voltammetry, which clearly exceeds the values reported for other manganese‐based catalysts. Moreover, the addition of water leads to the highest TOF_max value (ca. 320 000 s⁻¹) ever reported for a manganese‐based catalyst. A Mn^I tetracarbonyl intermediate was detected under catalytic conditions for the first time.

The chemical inertness of abundant and commercially available alkyl chlorides precludes their widespread use as reactants in chemical transformations. Presented in this work is a metallaphotoredox methodology to achieve the catalytic intramolecular reductive cyclization of unactivated alkyl chlorides with tethered alkenes. The cleavage of strong C(sp³)−Cl bonds is mediated by a highly nucleophilic low‐valent cobalt or nickel intermediate generated by visible‐light photoredox reduction employing a copper photosensitizer. The high basicity and multidentate nature of the ligands are key to obtaining efficient metal catalysts for the functionalization of unactivated alkyl chlorides.