As a final step, we sought to expand the scope in terms of potential C-S coupling reactions. While the partial current densities for C-S products was rather modest when using CO2 as the reactant, amounting to less than 5 mA/cm 2 , we reasoned that potentially more active Cprecursors that can be produced from CO2 reduction would lead to enhanced rates (Fig. ). To this end, we maintained identical reaction conditions (-1.18VRHE, 200 mM SO3 2-in 1 M KOH) and substituted 200 mM of CH3OH, HCOO -, CH2O or CH3COO -in place of CO2. Indeed, we was that the formation of SA was greatly increased by up to 2 orders of magnitude for CH3OH and by 30X for HCOO -(Fig. ). Note, no products were observed if SO3 2-and the C-reactants were simply mixed in the electrolyte (Fig. ). The equilibration with methanediol in alkaline media likely prevented formaldehyde from directly coupling with SO3 2-through nonelectrochemical steps. We chose to use formation rate as a metric of comparison as the precise mechanism and electron transfer steps are not yet unambiguous. This set of results indicates that a variety of partially reduced CO2 products species may act as effective building blocks for C-C and C-S bond formation. Strategies for C-S product synthesis with increased rates could then entail the use of flow reactors utilize a CO2 activation catalyst (e.g. Sn or Bi -based materials selective for HCOO -) and a secondary C-S coupling catalyst (Cu in this work but other materials may yet be better). Interestingly, HMS was not observed in these experiments, and this can be rationalized as the reactants used did not feature the key intermediates of *COH or *CHOH as calculated above.