“…12,20−24 However, the obvious challenging problems for the noble metal-based catalysts are expensive, easily sintered, volatile, and poisoned in the presence of water, sulfur, and other reactive gases during the operation. 1,3,4,16,25 In contrast, transition-metal oxides arise as methane combustion catalysts in the market mainly due to the low cost and operation stability. 2,6,7,10,13,26,27 Among the transition-metal oxide catalysts, copper oxide, especially in the form of nanoparticles (NPs), has shown to be a promising substitute to noble metal-based catalysts.…”