Table 2. Calculated Gibbs Free Energies (in eV/mol) at Room Temperature of the Steps of CO₂ Reduction over Pristine and Oxidized AuSn₄ (Denoted as “ox-AuSn₄”) Surface.

step	reaction/substrate (*)	AuSn4	ox-AuSn4
1	H2 + * → 2(*-H)	0.98	–3.30
2	CO2 physisorption	0.83	0.35
3	CO2 + 2(*-H) → *-H + *-COOH	–1.20	–1.77
4	*-H + *-COOH → *-H + *–OH + *-CO	0.38	1.26
5	*-H + *-OH + *-CO → *-CO + *-H2O	-0.77	1.25
6	desorption of CO and H2O	-0.24	–0.93