Bef ore CO2ER, the surf ace of all the as-synthesized materials, CO and HCOO -selective bimetallic f oams, is predominated by Cu + species (≥65%) with a small contribution from metallic Cu (≤20%) and Cu 2+ (~25%). It is worth mentioning here that some of the as-synthesized catalyst compositions (Cu85In15, Cu25In75 and Cu40Sn60) did not display any Cu 2+ surf ace species, but exhibited mainly Cu + species with a low metallic copper contribution, Figure and Figure .