CO₂ Electrochemical Reduction to Methane and Methanol on Copper-Based Alloys: Theoretical Insight

Abstract

We performed a systematic investigation of CO2 electroreduction to CH4 and CH3OH on copper-based alloys stepped surfaces using density functional theory calculations associated with the standard hydrogen electrode model. We determined the correlations between CO adsorption energy and the other key C x H y O z intermediates adsorption energy, the overpotential, the limiting-potential elementary step, and selectivity to CH4, CH3OH, HCOOH, and H2. The electrode efficiency decrease by OH* poisoning and the H2 evolution is also investigated. The results demonstrate that the CO* protonation is the limiting-potential step on most surfaces, with the exception on Cu3Au and Cu3Co surfaces. In spite of the excessive strong CO* interaction on some surfaces, the overpotentials reduce when the degree of CO* adsorption energy and HCO*/COH* adsorption energy decoupling increases. The CO* adsorption energy is a good descriptor for linear scaling correlations with the other C x H y O z intermediates due to the similar charge transfer characteristics of the C–O bond in CO* and those intermediates. The formic acid production can be efficiently catalyzed on Cu3Pt, Cu3Ni, Cu3Co, and Cu3Rh surfaces. Methanol production is favorable on Cu3Pd and Cu3Pt surfaces, yet they show high overpotential (∼0.7 V). The key of methanol selectivity is CH2OH* intermediate formation favorability associated with the preference of CH2OH* protonation at the C atom over the O atom. The calculations reveal that the electroreduction activity on Cu-based alloys catalysts do not show a volcano-type relation as was previously found on pure metal catalysts.

Electrodeposited Cu-Sn Alloy for Electrochemical CO2 Reduction to CO/HCOO−

“…Cu 100 exhibited high current density despite the large CT resistance, because it showed a high FE for multielectron reduction products, including CH 4 and C 2 H 4 (Fig. 5a) [18,[38][39][40]. Briefly, CO 2 first adsorbs and reduces on Cu surface by accepting an electron and proton, and then forms surface HOCO (*HOCO), which is adsorbed on the electrode.…”

“…At present, the factor responsible for changing C 1 and C 2 selectivity is not evident; however, the aforementioned results yield useful knowledge in terms of selectivity control. DFT calculations have established that the selectivity of CO 2 RR is enhanced by using alloys [17][18][19]. Alloying controls the binding energy of the CO 2 RR reactive species to the electrode surface by changing the metal species and content ratio.…”

Investigation of Electrocatalysts for Selective Reduction of CO2 to CO: Monitoring the Reaction Products by on line Mass Spectrometry and Gas Chromatography

“…19,[25][26][27][28][29][30][31] For copper, its ability for hydrocarbon formation is mainly associated to its moderate CO binding energy, which leads Cu to sit near to the top of a volcano type relation of the limiting-potentials curves of CO 2 → COOH* and CO* → CHO* steps (*: adsorption site) as a function of the CO binding energy, as discussed by Peterson and Nørskov. 32 For Pt and Ni, for example, HER dominates over the CO 2 reduction.…”

“…12 Metallic electrocatalysts have been commonly investigated in aqueous electrolyte such as gold, [13][14][15] , and they produce HCOO -as the major product; (ii) Au and Ag have medium hydrogen overpotential, and weak CO adsorption properties, and their major product is CO; (iii) Ni, Fe and Pt have low hydrogen overpotentials and strong CO adsorption, and the major product is H 2 (water electroreduction); (iv) Cu is single in this group and is able to reduce CO 2 to more reduce species such as CH 4 and C 2 H 4 . 19,[25][26][27][28][29][30][31] For copper, its ability for hydrocarbon formation is mainly associated to its moderate CO binding energy, which leads Cu to sit near to the top of a volcano type relation of the limiting-potentials curves of CO 2 → COOH* and CO* → CHO* steps (*: adsorption site) as a function of the CO binding energy, as discussed by Peterson and Nørskov. 32 For Pt and Ni, for example, HER dominates over the CO 2 reduction.…”

Liquid Hydrocarbon Production from CO2: Recent Development in Metal‐Based Electrocatalysis

“…[197][198][199] The study established the role of cations in the electrolyte in converting CO 2 into CH 3 OH; for instance, an electrolyte containing trivalent cations such as La 3 + and Nd 3 + would exhibit af aster CO 2 reduction rate to CH 3 OHthan onewith single-valentcations such as Na + .Furthermore, theoretical calculations with Cu-based catalysts also advocate new alloy combinations as such calculations show that alloyingC uw ith other metals, such as Pd and Pt, mayr esult in higher CH 3 OH production rates. [200] 2.2.5. Future directions for methanol production From ap ractical standpoint, the catalysts currently utilized for the electrochemical reduction of CO 2 to CH 3 OH are far from ideal.…”