Fig. 4: Overall conversion efficiency operating envelope for PEC separations.
a–c The minimum overall efficiency for the separation to be feasible, ηSC,min (solid blue lines), and the maximum overall efficiency attainable, ηSC,max (solid orange lines), shown for water treatment at the household (a) and industrial (b) scales, and resource extraction (c). Increases in ηSC,min and reduction in ηSC,max as a function of decreasing Faradaic efficiency ηF are also indicated using dashed blue and orange lines, respectively. Note that these orange dashed lines follow the solid orange lines at lower cinitial before sharply curving downwards at higher cinitial in (a, b). d–f The corresponding limits on the semiconductor bandgap that may be used, as a result of finite current draw (i.e., current matching requirements, with the appropriate consideration of Faradaic efficiency) are shown for operation at the three scales of operation, along with decreases in these limits due to decreases in Faradaic efficiency.
