Electrochemical Routes for Upgrading Carbon-based Greenhouse Gases

Investigating electrocatalytic routes to upgrade prevalent greenhouse gases (GHGs) like CO2 and CH4 offers opportunities for sustainable manufacturing of value-added commodities (e.g., C2H4, CH3OH). Moreover, the availability of "cheap electrons" makes this route more attractive. It opens the potential to achieve a high reaction rate, high control over product selectivity, relatively milder operating conditions, and an excellent avenue for large-scale industrial applications. The central focus of this work is to advance experimental and computational methods to develop highly efficient electrochemical systems for CO2 capture, clean energy production & storage and to understand the dynamics at the electrode-electrolyte interface to gain mechanistic insight into sustainable electrochemical reactions. This work describes the prototyping of such electrochemical systems for capturing CO2 and converting CO2 & CH4 to fuels and value-added products. It encapsulates a combination of experimental and computational approaches in setting up an electrochemical system involving syntheses and characterization of electrocatalysts, designing & fabricating electrochemical reactors, fundamental insights into reaction mechanisms, and accessing the scope of scaling up such processes

Kinetic Studies of CO₂ Capture Using K₂CO₃/Activated Carbon in Fluidized Bed Reactor

In the present work, the capture of CO₂ by the low-temperature solid sorbent K₂CO₃ coated on activated carbon in a fluidized bed reactor is studied. A 30 wt % of K₂CO₃ coated on activated carbon prepared by a wet impregnation method and characterized by SEM, EDX, and BET analyses is used as the sorbent. The pressure drop characteristics of the fluidized bed are studied using a humidified mixture of air and CO₂ as the fluidizing medium to identify the minimum fluidization velocity. The minimum fluidization velocity increases with an increase in CO₂ concentration and sorbent particle size and a decrease in temperature. Kinetic studies of CO₂ capture are carried out in the fluidized bed reactor by directly measuring the solid conversion as a function of time. The experimental results show that the conversion of K₂CO₃, for a given time, increases with increase in CO₂ concentration, fluidization velocity, temperature, and the height of the static bed, and decreases with the increase in sorbent particle size. The model proposed by Avrami for noncatalytic gas–solid reactions is modified and fitted for the kinetic studies which satisfactorily predict the experimental data

Chloride-Promoted High-Rate Ambient Electrooxidation of Methane to Methanol on Patterned Cu–Ti Bimetallic Oxides

The selective electrochemical methane oxidation reaction (MOR) has been challenging due to higher CH4 activation barriers and lower solubility at ambient conditions. Here, we synthesize a conductive gas-diffusion layer patterned with alternating squares of Cu and Ti oxides to achieve highly selective MOR at interfaces consisting of Cu–Ti bimetallic oxides. We observe high MOR faradaic efficiencies of ∼28% at ambient conditions and ∼72% at near-ambient conditions (40 °C) to value-added products such as CH3OH and HCOOH in a Cl–-mediated environment. Density function theory calculations suggest that despite TiO2 exhibiting barrierless thermochemical methane dissociation, an electrochemical oxidation pathway is likely competitive at high overpotentials. The unprecedented current densities of ∼10 mA/cm2 for HCOOH and ∼16 mA/cm2 for CH3OH, along with these insights on ambient MOR, will enable the development of highly efficient electrochemical systems for the utilization of CH4

Chloride-Promoted High-Rate Ambient Electrooxidation of Methane to Methanol on Patterned Cu–Ti Bimetallic Oxides

The selective electrochemical methane oxidation reaction (MOR) has been challenging due to higher CH4 activation barriers and lower solubility at ambient conditions. Here, we synthesize a conductive gas-diffusion layer patterned with alternating squares of Cu and Ti oxides to achieve highly selective MOR at interfaces consisting of Cu–Ti bimetallic oxides. We observe high MOR faradaic efficiencies of ∼28% at ambient conditions and ∼72% at near-ambient conditions (40 °C) to value-added products such as CH3OH and HCOOH in a Cl–-mediated environment. Density function theory calculations suggest that despite TiO2 exhibiting barrierless thermochemical methane dissociation, an electrochemical oxidation pathway is likely competitive at high overpotentials. The unprecedented current densities of ∼10 mA/cm2 for HCOOH and ∼16 mA/cm2 for CH3OH, along with these insights on ambient MOR, will enable the development of highly efficient electrochemical systems for the utilization of CH4