Plasma-Enabled Active Site Regeneration for Selective Liquid Fuel Production across Catalyst Binding Regimes in CH ₄ -CO ₂ Conversion

The selective conversion of CH 4 and CO 2 to liquid fuels at mild conditions is constrained in thermal catalysis by linear scaling relationships, surface poisoning, overoxidation of oxygenate intermediates, and adsorption−desorption kinetics tied to a single gas temperature. Plasma-enabled catalysis circumvents some of these limitations through nonequilibrium excitation of molecular reactants, but sustained performance remains limited by catalyst deactivation and by an incomplete understanding of how plasma-generated species interact with catalyst surfaces. Here, we establish that plasma-catalytic CH 4 -CO 2 conversion at mild conditions (surface temperature, T sur = 473 K, 1 atm) is governed by the interplay between plasma excitation and catalyst binding strength, which together determine surface speciation, product selectivity, and catalyst deactivation. Using time-resolved selectivity measurements, surface characterization, and density functional theory (DFT)-informed microkinetic modeling on Cu(111) and Ni(111), we show that plasma-driven dissociative chemisorption accelerates bond-breaking of CH 4 and CO 2 without altering surface thermochemistry. Because plasma excitation and surface reaction energetics are decoupled, the system is driven into one of two intrinsic deactivation regimes set by metal−adsorbate interactions, in which weakly binding catalysts such as Cu accumulate O* and strongly binding catalysts such as Ni accumulate CH x *. We then demonstrate a plasma-enabled strategy for continuous active-site regeneration that couples plasma-driven dissociative chemisorption with targeted co-reactant activation, selectively removing surface poisons without altering CH 4 or CO 2 dissociative chemisorption rates. On Cu, plasma-excited co-reactant species restore CH 3 O* intermediates and triple methanol selectivity. On Ni, accumulated CH x * fragments are removed and C−C coupling reactivates, doubling C 2 hydrocarbon yield. These results identify how plasma excitation and catalyst binding strength together tune surface intermediates and product selectivity and expand the design space of heterogeneous catalysis for one-step conversion of CH 4 and CO 2 at mild conditions.