Fig. 1. (a) LSVs of a Cu-wire electrode in 0.1 M Na₂SO₄ at pH = 6.8 (dotted black line), in the presence of 0.1 M fructose (full black line), or 0.1 M glucose (continuous orange line); and (b) in the presence of 0.1 M fructose at four different pHs: 0.1 M Na₂SO₄ at pH = 6.8 (black), 0.18 M phosphate buffer solution (PBS) at pH = 7.5 (red), 0.12 M PBS at pH = 11.3 (green), and 0.5 M carbonate buffer solution (CBS) at pH = 10.6 (blue). The voltammetries were run at a 10 mV s⁻¹ scan rate at room temperature (21 °C) with a Nafion membrane separator. The potential range used in each experiment depends on the pH, with the reductive potential varied until ca. −5 mA cm⁻² was reached. The small reduction peak observed at ca. 0 V vs. RHE for the fructose LSV is attributed to the reduction of oxidised Cu species, as discussed in Section S4 and Fig. S16–S19.†.