Green hydrogen plays a crucial role in decarbonization and the future of low-carbon society. Still, its transport/distribution and cost of production, mainly realized by electrolysis, are major hurdles. Liquid H₂ carriers reduce transport/distribution costs but add further expenses for their production. To address this challenge, we proposed a novel strategy for electrocatalytic production of a liquid organic hydrogen carrier with anodic valorization of the process. This review summarizes the state of the art and outlooks in this new concept. The electrocatalytic process is briefly introduced, and the main components are discussed. Subsequently, the electrocatalytic production of liquid organic hydrogen carriers and anodic oxidation from components to processes, together with the paired processes and reactors, are analyzed, highlighting challenges and prospects.

The stoichiometric conversion of methane to methanol by Cu-exchanged zeolites can be brought to highest yields by the presence of extraframework Al and high CH₄ chemical potentials. Combining theory and experiments, the differences in chemical reactivity of monometallic Cu-oxo and bimetallic Cu-Al-oxo nanoclusters stabilized in zeolite mordenite (MOR) are investigated. Cu-L₃ edge X-ray absorption near-edge structure (XANES), infrared (IR), and ultraviolet-visible (UV-vis) spectroscopies, in combination with CH₄ oxidation activity tests, support the presence of two types of active clusters in MOR and allow quantification of the relative proportions of each type in dependence of the Cu concentration. Ab initio molecular dynamics (MD) calculations and thermodynamic analyses indicate that the superior performance of materials enriched in Cu-Al-oxo clusters is related to the activity of two μ-oxo bridges in the cluster. Replacing H₂O with ethanol in the product extraction step led to the formation of ethyl methyl ether, expanding this way the applicability of these materials for the activation and functionalization of CH₄. We show that competition between different ion-exchanged metal-oxo structures during the synthesis of Cu-exchanged zeolites determines the formation of active species, and this provides guidelines for the synthesis of highly active materials for CH₄ activation and functionalization.

Cu-exchanged zeolites are known to be active in the selective oxidation of methane to methanol at moderate temperatures. Among them, Cu-exchanged mordenite (MOR) is the system that has so far shown the highest methanol yield per Cu atom. This high efficiency is attributed to the ability of MOR to selectively stabilize an active tricopper cluster with a [Cu ₃ (μ-O) ₃ ] ²⁺ structure when activated in the presence of O ₂ at high temperatures. In this study, we investigate the elementary steps in the formation of [Cu ₃ (μ-O) ₃ ] ²⁺ by in situ X-ray absorption spectroscopy and ultraviolet-visible spectroscopy. We demonstrate that the Cu cations undergo a series of thermally driven steps during activation that precede the formation of the active oxidizing species. We hypothesize that the thermal formation of highly mobile Cu ⁺ species by autoreduction of Cu ²⁺ in an inert gas is essential to enable the reorganization of Cu ions in MOR, which is necessary for the formation of a reduced precursor of [Cu ₃ (μ-O) ₃ ] ²⁺ . Such a precursor can be oxidized in the presence of strong oxidants-such as O ₂ and N ₂ O-to form active [Cu ₃ (μ-O) ₃ ] ²⁺ at temperatures as low as 50 °C.