Hydrogen absorption by palladium electrode polarized in sulfuric acid solution containing surface active substances—I. The cathodic region

Direct H2O2 Synthesis, without H2 Gas

We report here the direct hydrogenation of O₂ gas to form hydrogen peroxide (H₂O₂) using a membrane reactor without H₂ gas. Hydrogen is sourced from water, and the reactor is driven by electricity. Hydrogenation chemistry is achieved using a hydrogen-permeable Pd foil that separates an electrolysis chamber that generates reactive H atoms, from a hydrogenation chamber where H atoms react with O₂ to form H₂O₂. Our results show that the concentration of H₂O₂ can be increased ∼8 times (from 56.5 to 443 mg/L) by optimizing the ratio of methanol-to-water in the chemical chamber, and through catalyst design. We demonstrate that the concentration of H₂O₂ is acutely sensitive to the H₂O₂ decomposition rate. This decomposition rate can be minimized by using AuPd alloy catalysts instead of pure Pd. This study presents a new pathway to directly synthesize H₂O₂ using water electrolysis without ever using H₂ gas.

The influence of surfactants on the electrocatalytic hydrogenation of organic compounds in micellar, emulsified, and hydroorganic solutions at Raney nickel electrodes

The electrocatalytic hydrogenation (ECH) of limonene (1) and carvone (4) at a Raney nickel cathode was studied both in hydroorganic medium (methanol–water) and aqueous micellar and emulsified solutions. In methanol–water, the ECH of 1 stopped at p-menthene (2) and proceeded with low current efficiencies (18–24%). In micellar solutions containing a cationic surfactant (CTAB), the ECH of 1 was more efficient, giving p-menthane (3) as the main product with current efficiencies up to 30%. The pH of the solution (hydroorganic and micellar) had little influence. With anionic (SDS) and nonionic (Brij 35) surfactants, some p-menthane (3) was formed but the conversion rate and current efficiency were much lower. The ECH of carvone (4) was slightly less efficient in methanol–water than in micellar and emulsified solutions. The saturated alcohols neocarvomenthol (8), carvomenthol (9), isocarvomenthol (10), and neoisocarvomenthol (11) were the main products with current efficiencies of 75% (hydroorganic medium) to 90% (micellar solutions). The effect of surfactant concentration and pH on the efficiency and stereochemistry of the ECH of carvone (4) was also studied. Keywords: electrocatalytic hydrogenation, limonene, carvone, Raney nickel, micellar medium.