Table 21.

PCET Thermochemistry of Carbon Dioxide Reduction^a

CO2(g) + H2(g) → HCOOH	solvent		E∘(V vs H2)	−ΔG∘/nb
CO2/HCOOH	gas		−0.22542
CO2/HCOOH	H2O		−0.114327
CO2(g) + H2(g) → CO(g) + H2O	solvent	E∘(CO2/CO2•−)	E∘(V vs H2)	−ΔG∘/nb
CO2/CO	gas	–	−0.14842	45.2
CO2/CO	H2O	−1.99376	−0.10467	50.4
CO2/CO	DMF	−2.01377,c	−0.06867	50.7
CO2/CO	MeCN	–	–0.09267	49.8
CO2/CO	DMA	–	–0.1051
CO2(g) + 4H2(g) → CH4(g) + 2H2O	solvent		E∘(V vs H2)	−ΔG∘/nb
CO2/CH4	gas		0.14542	51.9
CO2/CH4	H2O		0.16967	56.7
CO2/CH4	MeCN		0.17867	56.5
CO2/CH4	DMF		0.18267	56.1

^aPotentials for 1e⁻ reductions are in V vs SHE if in aqueous solution and V vs Cp₂Fe^+/0 if they are in organic solution. Values for E^∘(V vs H₂) are in V; – eE^∘ is the average free energy for $\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.{\text{H}}_{2(\text{g})}$ addition. −ΔG^∘/n values are average free energies for the overall reaction in kcal mol⁻¹.

^b−ΔG^∘/n values are for the overall reaction shown except to form H^• [rather than add H₂(g)] (see Section 4) and were calculated from E^∘(V vs H₂) using eq 18.

^cStandard state converted to 1 atm of CO₂ based on Henry’s Law constant reported in ref 378.