The role of water and copper oxide in methane oxidation using AuPd nanoparticle catalysts

• Au, Pd, AuPd, and AuPd-CuO x catalysts are used for methane oxidation. • The synergistic effect of alloying Pd with Au is demonstrated below 200 °C. • Below 200 °C, methane oxidation rates correlate strongly with bound water. • Wet feed is shown to decrease the selectivity to CO. • Water enhances methane adsorption on AuPd-CuO x . Methane shows great potential as a chemical feedstock, but conversion to value-added products remains a significant challenge. Selective oxidation of methane at moderate temperatures and pressures has gained momentum, with AuPd nanoparticles showing promise for methane activation. The formation of different surface intermediates is illustrated through studies with different temperatures and reaction feed compositions. The relationship between these surface intermediates and the selectivity and activity are shown. One hypothesis is that water and stabilization materials such as copper oxide facilitate selective oxidation of methane. To test this hypothesis, TiO 2 -supported AuPd nanoparticles with and without a copper oxide stabilizing material are used in wet and dry feed conditions. It is observed that AuPd catalysts are more active than monometallic Au and Pd catalysts at temperatures below 200 °C when water is present on the catalyst surface. Additionally, methane oxidation rates increase with unprotonated formate. The presence of CuO x improves methane adsorption and selectivity towards CO over CO 2 , but CuO x decreases overall methane consumption.