Abstract
Electrochemical reduction of CO2 to useful chemical and fuels in an energy efficient way is currently an expensive and inefficient process. Recently, low-cost transition metal-carbides (TMCs) have been proven to exhibit similar electronic structure similarities to Platinum-Group-Metal (PGM) catalysts and hence, can be good substitutes for some important reduction reactions. In this work, we test graphene-supported WC (Tungsten Carbide) nanoclusters as an electrocatalyst for the CO2 reduction reaction. Specifically, we perform density functional theory (DFT) studies to understand various possible reaction mechanisms and determine the lowest thermodynamic energy landscape of CO2 reduction to various products, such as CO, HCOOH, CH3OH, and CH4. This in-depth study of reaction energetics could lead to improvements and development of more efficient electrocatalysts for CO2 reduction.
Highlights
The carbon dioxide (CO2 ) is very stable under environmental conditions, and reduction to some hydrocarbon products is an endothermic process
2 electrochemical reaction itsmechanism thermodynamics more complex toisstudy compared oxygen reduction reactionreduction (ORR), and itsisthermodynamics more when complex to studytowhen compared to oxygen hydrogen evolution reaction (HER), and other reactions involving the transfer of fewer proton–electron reaction (ORR), hydrogen evolution reaction (HER), and other reactions involving the transfer of pairs
We have presented an improved understanding of CO2 reduction reaction mechanisms and provided the lowest energy pathway for various products
Summary
The carbon dioxide (CO2 ) is very stable under environmental conditions, and reduction to some hydrocarbon products is an endothermic (or endergonic) process. Metal terminated WC exhibited good activity for hydrogen evolution reaction (HER) and WC coated with Fe when tested for CO2 reduction are selective towards methane formation This is because electronic properties of W atoms surrounding. Among different metal-carbides, tungsten carbide (WC) based compounds are widely studied electrocatalysts [22] They are investigated in various forms, such as: Alloys to combine the electronic properties of WC with other metal(s), for example, Tantalum doped WC displayed better activity towards hydrogen evolution (HER) when compared to unmodified WC [23]. Ni with WC nanocluster for urea electro-oxidation showed high tolerance towards CO poisoning, and high stability thereby enhancing catalyst activity [30] All these studies explain that TMCs have the potential to work as better catalysts making them an attractive alternative for traditional metallic catalysts in some of the industrially relevant catalytic reactions. Results from the current work explain that the reduction to CH3 OH on graphene supported WC is thermodynamically favorable at higher negative potentials compared to reduction to CH4 , which is in qualitative agreement with the results from the literature
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