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.

The abundant yet widely distributed methane resources require efficient conversion of methane into liquid chemicals, whereas an ambient selective process with minimal infrastructure support remains to be demonstrated. Here we report selective electrochemical oxidation of CH₄ to methyl bisulfate (CH₃OSO₃H) at ambient pressure and room temperature with a molecular catalyst of vanadium (V)-oxo dimer. This water-tolerant, earth-abundant catalyst possesses a low activation energy (10.8 kcal mol^‒1) and a high turnover frequency (483 and 1336 hr^-1 at 1-bar and 3-bar pure CH₄, respectively). The catalytic system electrochemically converts natural gas mixture into liquid products under ambient conditions over 240 h with a Faradaic efficiency of 90% and turnover numbers exceeding 100,000. This tentatively proposed mechanism is applicable to other d⁰ early transition metal species and represents a new scalable approach that helps mitigate the flaring or direct emission of natural gas at remote locations.