Table S7.

Corrected free-energy barriers (ΔG^‡, in electronvolts) and corrected free-energy differences (ΔG, in electronvolts) for various reduction steps of CH₄ formation on Cu(100) at pH 7 and 298 K

ID	Reaction equation	ΔG‡, eV	ΔG, eV
1	$\text{*CO}+\text{H*}\to \text{*CHO}$	0.96	0.89
1a	$\text{*CO}+{\text{H}}_2\text{O}+e^{-}\to \text{*CHO}+{\text{OH}}^{-}$	0.97	0.82
1b	$\text{*CO}+{\text{H}}_2\text{O}+e^{-}\to \text{*COH}+{\text{OH}}^{-}$	1.21	1.07
2	$\text{*CHO}+{\text{H}}_2\text{O}+e^{-}\to \text{*CHOH}+{\text{OH}}^{-}$	0.24	0.05
2a	$\text{*CHO}+\text{H*}\to {\text{CH}}_2\text{O}$	1.01	0.50
3	$\text{*CHOH}+e^{-}\stackrel{{\text{H}}_2\text{O}}{\to }\text{*CH}+{\text{OH}}^{-}$	0.59	−0.19
3a	$\text{*CHOH}+\text{H*}\to {\text{*CH}}_2\text{OH}$	0.86	0.37
4	$\text{*CH}+{\text{H}}_2\text{O}+e^{-}\to {\text{*CH}}_2+{\text{OH}}^{-}$	0.40	0.15
4a	$\text{*CH}+\text{H*}\to {\text{*CH}}_2$	0.97	0.17
5	${\text{*CH}}_2+{\text{H}}_2\text{O}+e^{-}\to {\text{*CH}}_3+{\text{OH}}^{-}$	0.55	0.01
5a	${\text{*CH}}_2+\text{H*}\to {\text{*CH}}_3$	1.05	0.00
6	${\text{*CH}}_3+{\text{H}}_2\text{O}+e^{-}\to {\text{CH}}_4+{\text{OH}}^{-}$	0.81	−0.53
6a	${\text{*CH}}_3+\text{H*}\to {\text{CH}}_4$	0.86	−0.71

The work functions are referenced to the initial states.