A preliminary toxicological assessment raised a major health hazard concern surrounding the use of MeOH as the organic solvent: once absorbed, MeOH metabolism presents high toxicity due to the formation of formic acid, which can lead to organ damage, in particular to the eye tissues. Therefore, EtOH was tested under otherwise identical reaction conditions (Table , entry 6). Gratifyingly, this replacement had a positive influence on the reaction outcome, and a substantial increase in the yield was observed (89 vs 77% yield, Table , entry 6 vs entry 5). Other organic solvents were also tested under otherwise identical reaction conditions as those from Table , entry 6. In ethylene glycol (Table , entry 7), a good yield of 67% was also obtained, whereas in acetone (Table , entry 8), the yield under the optimized [H2SO4]aq. / solvent ratio (i.e. 3:1 v/v), was essentially the same as when using a [H2SO4]aq. / solvent (1:1, v/v) (entry 8 vs entry 1). A full optimization table is presented in Table . We also optimized the ECH of 2-cyclohexenone (1b), as this substrate shows very different reactivity from that of 1a. Further, 1b was chosen for the LCA due to its industrial relevance in the production of nylon 6 and other related materials. . In a mixture 1:1 (v/v) of acetone and H2SO4 (0.5 M aq.), a very good yield of 94% was obtained, however the FE was rather low (Table , entry 1). With the aim of improving the FE, MeOH was tested as the solvent at a milder potential of -0.9 V. This gave a significant improvement in the FE, and a small decrease in the yield of 2b (Table , entry 2). We then varied the solvent ratio by increasing the amount of H2SO4 in the mixture (Table , entry 3), but this decreased the FE by a factor of 2. This lower FE is not surprising, due to the greater availability of protons for the HER. When the reaction was run with the same ratio of aqueous / organic solvent (3:1, v/v), but with lower acidity (Table , entry 4), the FE and the yield both increased. When EtOH was used instead of MeOH under otherwise identical reaction conditions (Table , entry 5 vs entry 4), both the yield and the FE (24%) increased further. The reaction was run on a larger scale of (0.154 g, 1.6 mmol, entry 6), which gave a 79% yield but a lower FE (9%). A lower potential could increase the FE, which occurred when the reaction was carried out at -0.7 V on a 0.4 mmol scale for 18 h (79% yield and FE of 14, Table , entry 7). However, an increase in concentration to 0.064 M of 1b led to a drop in conversion and yield (Table , entry 8). This was circumvented by an increase in acid concentration to 0.38 M, which resulted in an outstanding yield (94%) and a very high FE of 37%. Important to note is that there is a minimal production of byproducts (yield / conversion = 0.97). To consider the environmental impact of this process, the recyclability properties of the catalyst needed to be assessed. Consecutive hydrogenation reactions of 1b were run for reaction times of only 2 h, leading to yields of ca 20%. This was so that we could compare activity differences (rates) from run to run, as well as differences in selectivities. The Ni foam was washed with EtOH after every consecutive catalytic run. The performance showed little variation for 15 runs, giving 2b in a 19.7 ± 1.6% yield (Scheme 2). After the completion of these 15 cycles, a decrease in mass of 7.24% was observed in the Ni foam. This decrease in mass is due to dissolution of Ni in the acidic media in the absence of electrical potential in between runs, as well as due to the sonication process required in the work-up. To rule out the leeching of nickel during operation, a reaction was performed for 30 h as equivalent in time to the recyclability study. No significant decrease in mass of the Ni foam electrode was detected after this test.