Methane (CH4) is becoming economically attractive carbon-based feedstock with the continuous discovery of shale gas and gas clathrates in addition to the conventional natural gas. The undesirable transportation cost for gaseous hydrocarbons of such large reserves especially stocked at remote locations, requires oxidative conversion of CH4 into valuable chemical feedstocks such as methanol (CH3OH). However, in traditional chemical methods, such process usually happened under high temperature & pressure, and confronted the challenge of catalytic species reproduction if using oxygen (O2) as terminal oxidant. Here, we present an electrochemical system for CH4 functionalization at ambient condition. Such a process was realized via the generation of nonequilibrium high-energy intermediates from the electrochemical oxidation of d0 metal-oxo species, which is not restricted by the oxidative capacity of O2. The turnover frequency (TOF) for the CH4 to CH3OH equivalent could on par with high temperature & pressure homogeneous system including universally used noble transition metals reported before, while our system employs more earth-abundant and economy available metal catalysts. Electrokinetic study was conducted to analyze the reaction order dependences for CH4 functionalization, the rate-determining step (RDS), and the formal activation energy, assisting by density functional theory (DFT) calculation for mechanism study. Furthermore, in view of the requirement of large-scale manufacture and assembly of fluidized electrochemical cell for industrial application, heterogeneous electrocatalyst with similar efficiency was also developed. This study provides a new platform for the ambient C-H activation of not only the CH4, but also other alkanes in general.

Electrocatalytic oxidation of d0-oxo for ambient methane functionalization

2019 Fall National Meeting

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