Electrocatalytic Methane Functionalization with d⁰ Early Transition Metals Under Ambient Conditions

The undesirable loss of methane (CH₄ ) at remote locations welcomes approaches that ambiently functionalize CH₄ on-site without intense infrastructure investment. Recently, we found that electrochemical oxidation of vanadium(V)-oxo with bisulfate ligand leads to CH₄ activation at ambient conditions. The key question is whether such an observation is a one-off coincidence or a general strategy for electrocatalyst design. Here, a general scheme of electrocatalytic CH₄ activation with d⁰ early transition metals is established. The pre-catalysts' molecular structure, electrocatalytic kinetics, and mechanism were detailed for titanium (IV), vanadium (V), and chromium (VI) species as model systems. After a turnover-limiting one-electron electrochemical oxidation, the yielded ligand-centered cation radicals activate CH₄ with low activation energy and high selectivity. The reactivities are universal among early transition metals from Period 4 to 6, and the reactivities trend for different early transition metals correlate with their d orbital energies across periodic table. Our results offer new chemical insights towards developing advanced ambient electrocatalysts of natural gas.