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Abstract The electrochemical CO2 reduction reaction (CO2RR) has gathered widespread attention in the past decade as an enabling component to energy and fuel sustainability. Copper (Cu) is one of the few electrocatalysts that can convert CO2 to higher-order hydrocarbons. We report the CO2RR on polycrystalline Cu from 5 °C to 45 °C as a function of electrochemical potential. Our result shows that selectivity shifts toward CH4 at low temperature and H2 at high temperature at the potential values between −0.95 V and −1.25 V versus reversible hydrogen electrode (RHE). We analyze the activation energy for each product and discuss the possible underlying mechanism based on their potential dependence. The activation barrier of CH4 empirically obeys the Butler–Volmer equation, while C2H4 and CO show a non-trivial trend. Our result suggests that the CH4 production proceeds via a classical electrochemical pathway, likely the proton-coupled electron transfer of surface-saturated COad, while C2H4 is limited by a more complex process, likely involving surface adsorbates. Our measurement is consistent with the view that the adsorbate–adsorbate interaction dictates the C2+ selectivity.
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Nanostructured molybdenum carbide on biochar for CO2 reforming of CH4
A simple procedure was developed to synthesize molybdenum carbide nanoparticles (Mo2C/BC) by carburization of molybdate salts supported on the biochar from pyrolysis of biomass without using extra carbon source or reducing gas. The molybdenum carbide formation procedure investigated by in-situ XRD and TGA-MS indicated that the phase transitions followed the path of (NH4)6Mo7O24·4H2O → (NH4)2Mo3O10 → (NH4)2Mo14O42 → Mo8O23 → Mo4O11 → MoO2 → Mo2C. The volatile gases CO, H2, and CH4 evolved from biochar and the biochar solid carbon participated in the reduction of molybdenum species, while the biochar and CH4 served as carbon sources for the carburization. Temperature programmed surface reactions of Mo2C/BC indicated that CH4 dissociated as CH4 ⇋ C∗ + 2H2 on the catalyst surface, and CO2 reacted as CO2 + C∗ ⇋ 2CO+ ∗ due to oxidation of Mo2C. Both experiment data and thermodynamic analysis for the study of operation conditions of CO2 reforming of CH4 clearly demonstrated that the yields of H2 and CO increased with the increased temperature and the reasonable conversions should be performed at 850 °C, at which both CH4 and CO2 conversions were higher than 80%.
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- Award ID(s):
- 1736173
- PAR ID:
- 10085389
- Date Published:
- Journal Name:
- Fuel
- ISSN:
- 0016-2361
- Page Range / eLocation ID:
- 403-410
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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