A high-performance, low Pd-loading and highly thermal conductive catalyst is developed by carburizing a thin-felt Pd/AlOOH/Al-fiber (0.25 wt% Pd) using ethylene. Carbon dissolving into the subsurface of Pd nanoparticles to form surface PdCx species (i.e., Pd@PdCx) leads to at least 2-fold improvement of the intrinsic activity (expressed by turnover frequency, TOF) for the CO oxidative coupling to dimethyl Oxalate, in nature, remarkably promoting the generation of key reaction intermediate of COCOOCH3* (*, a surface site).