Table 2. State-of-the-Art Electrochemical Reduction of CO₂ to Methanol.

catalysts	electrolyte	electrode/substrate	applied potential	overpotentiala/V	j/mA cm–2	%FEMeOH	other CO2RR product(s)	ref
Cu2O/Zn2O	0.5 M KHCO3	GDEb	–1.16 V vs Ag/AgCl	0.54	10	27.5 (17.7c)	C2H6O	Albo et al.25
Pd/SnO2 nanosheet	0.1 M NaHCO3	carbon paper	–0.24 V vs RHE	0.27	1.45	54.8	formate	Zhang et al.82
copper selenide (Cu1.63Se) nanoparticle	[Bmim]PF6d (30 wt %) /CH3CN/H2O (5 wt %)	carbon paper	–2.1 V vs Ag/Ag+ (−1.175 V vs RHE)	1.2	41.5	77.6	formate, CO	Yang et al.26
PYD@Cu–Pt alloye	0.5 M KCl	free standing electrode	–0.6 V vs SCE	0.07	22	37	formate	Yang et al.83
Cu2O-MWCNTsg	0.5 M KHCO3	Cu foil	–0.8 V vs Ag/AgCl	f	6	38	not reported	Irfan Malik et al.84
Cu nanocluster/ZnO	0.1 M KHCO3	single crystal ZnO	–1.4 V vs Ag/AgCl	0.83	12	2.8	CO, CH4, C2H4, C2H6O, methyl formate	Andrews et al.85
Ni	0.1 M KHCO3	Ni foil	–1.0 V vs RHE	1.03	5	2.3	CH4, C2H4, formate	Kuhl et al.86
BDDh	1 M NH3	Si wafer	–1.3 V vs Ag/AgCl	0.67	f	24.3	CO, CH4	Jiwanti et al.87
dehydrogenases	0.05 M phosphate buffer pH 7.6	carbon felt	–1.2 V vs Ag/AgCl	0.58	0.08	10	not observed	Schlager et al.37
dehydrogenases modified graphene	0.1 M TRIS-HCl buffer pH 7.0	carbon felt	–1.2 V vs Ag/AgCl (−0.58 V vs RHE)	0.61	1	12	not observed	This work

^aOverpotential is compared with the thermodynamic potential for the conversion of CO₂ to methanol of 0.03 V vs RHE⁸⁶ where E (V vs RHE) is calculated from E(V vs Ag/AgCl) + 0.205 V + 0.0591*pH or E(V vs SCE) + 0.244 V + 0.0591*pH.

^bGDE: gas diffusion electrode.

^cThe experiment was performed without supplying CO₂ to GDE.

^d[Bmim]PF₆:1-butyl-3-methylimidazolium hexafluorophosphate.

^ePYD: 4-(3-phenoxy-2,2-bis(phenoxymethyl)propoxy)pyridine.

^fThe information was not given.

^gMultiwall carbon nanotubes (MWCNTs) impregnated with Cu₂O.

^hBoron-doped diamond electrode.