1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 Obtaining C 2 and C 3 Products from Methane Using Pd/C as Anode in a Solid Fuel Cell-type Electrolyte Reactor Andrezza S. Ramos, [a] Monique Carolina L. Santos, [a] Camila M. Godoi, [a] Almir Oliveira Neto, [a] and Rodrigo Fernando B. De Souza* [a] Methane was converted into C2 and C3 products under mild conditions using a single stage solid electrolyte reactor, using a proton exchange membrane fuel cell as a SER-FC and Pd/C as an electrocatalyst prepared by the reduction method of sodium borohydride. This electrocatalyst has a cubic pattern of palladium centered on the face and an average size of nanoparticles close to 6.4nm, according to the literature. Differential mass spectrometry reveals the chemical profile of species obtained from the oxidation of methane with ionic currents (Ii) at m/z = 16,28,30,32,44,46and60.Inmanycases, Ii can be assigned to more than one species; therefore, complementary ATR-FTIR experiments were performed. The ATR-FTIR spectra confirmed the presence of C2 and C3 compounds such as ethane, ethanol, acetaldehyde, acetic acid and propane. Considering the low amount of water in the reaction medium, these results may be associated with the use of Pd/C electrocatalysts responsible for the activation of the water molecule. The availability of natural gas currently rivals with oil; however, this hydrocarbon is not as versatile as crude oil. [1] The main component of natural gas is methane, the most stable hydro- carbon, with the very high dissociation energy of C  H bond (435kJmol 1 ). [2] Its tetrahedral structure is difficult to polarize; therefore, it makes this molecule almost inert to mild conditions. [3] Turning this gas into higher value-added products is a great goal. Current approaches to utilization of methane involve mainly high-temperature processes to produce syngas (H 2 + CO), which further can be transformed into methanol or fuels. [2] The ethane is a vital building block in the chemical industry with an expectedly of increasing demand in obtaining C2 or longer compounds. [4] The oxidative coupling of methane (OCM) is a direct and exothermic process and not limited by any thermodynamic constraints. [1a] The key of OCM reaction is the formation of methyl radicals. This radical, in the gas phase, reacts with methane to form ethane and other products. [1b,5] However, the OCM reaction is fulfilled at high temperature (above 600°–800 °C); a condition that allows methane combustion and the reaction that competes with the generation of CO and H 2 to occur. [6] Otherwise, similar to what happens on OCM reaction in high temperature, the methane can be activated at mild condition when the water activation generates “reactive oxygenated species” (ROS) as a HO * species. This radical causes the methane C  H bond scission leading to the reactive methyl radical formation, which in turn reacts with water molecules to produce methanol and hydrogen. [7] These routes occur by like Fenton-reaction, [7a] or photo catalysis [8] and electrocatalysis. [9] As cited, the methyl radical that reacts with water molecules does not produce more complex species than methanol and its oxidation products. Due to most photochemical and electro- chemical processes occur in aqueous medium, products with C2 or C3 are rarely observed. The electrochemical reactors like solid electrolyte reactors – fuel cell type (SER-FC) are basically composed by two electrodes separated by an ion-conducting polymer that can operate in continuous flow; due to the solid electrolyte, the amount of water present in the reactional medium is drastically lower than electrochemical cell medium. [10] Proton exchange membrane fuel cell (PEMFC) was initially built to operate with H 2 and O 2 ; [11] this device allows that the formed radicals have higher chances to collide with other molecules containing carbon in the aqueous medium and, thereby, to occur their carbon chain growth. In the last years, some authors have studied the application fuel cells at low temperatures for partial oxidation of methane at mild conditions; [12] the most bountiful products were the methanol or formate species, additionally other products such as isopropanol and acetaldehyde are reported with less frequency. [12b] However, there are still little accumulated data on the subject, as a novel electrocatalysts and material flux. [9b] The palladium is still frequently employed as anodic electrode for the activation of small organic molecules in PEMFC. [12c,13] Winiwarter et al. [13a] showed that Pd could be promising for the application in this reactor type, because for this metal (M) there is formation of a thin layer of PdO (M  O) on electrocatalyst surface, where the oxide can activate the C  H bond in methane [14] and the water molecule; [15] it is also utilized for hydrocarbon oxidation, [16] due to its carbophilic properties. In this work, the application of solid electrolyte reactors (SER) PEMFC-type in mild conditions was studied to [a] Dr. A. S. Ramos, M. C. L. Santos, C. M. Godoi, Dr. A. Oliveira Neto, Dr. R. Fernando B. De Souza Centro de Celula a Combustivel e Hidrogenio Instituto de Pesquisas Energéticas e Nucleares, IPEN/CNEN-SP Av. Prof. Lineu Prestes, 2242 Cidade Universitária, CEP 05508–000, São Paulo, SP (Brazil) E-mail: aolivei@ipen.br Supporting information for this article is available on the WWW under https://doi.org/10.1002/cctc.202000297 ChemCatChem Communications doi.org/10.1002/cctc.202000297 1 ChemCatChem 2020, 12,1–6 © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim These are not the final page numbers! ��