Effective Hydrogen Peroxide Production from Electrochemical Water Oxidation

Abstract

The two-electron water oxidation reaction (2e – WOR) is progressively gaining traction as a sustainable approach for in situ electrosynthesis of hydrogen peroxide (H2O2). State-of-the-art 2e – WOR electrocatalysts have shown great promise at low electrical currents yet exhibit diminished electrocatalytic capabilities at larger current densities. Herein, by tailoring the boron doping level of boron-doped diamond (BDD) microfilms, we have fabricated an active, selective, and stable electrocatalyst for the 2e – WOR. Experimentally, we find that our modulated BDD films achieve a peak faradaic efficiency of 87%, as well as a record H2O2 production rate of 76.4 μmol cm–2 min–1, while maintaining a stable electrochemical performance for 10 h at 200 mA cm–2 in carbonate-based solutions. The results reported in this work firmly establish BDD as a primary catalyst candidate for large-scale implementation of the 2e – WOR and synchronously unlock new research avenues for the next-generation design of sp3-structured carbonaceous materials for anodic H2O2 electrosynthesis from water.

Carbonate‐Induced Electrosynthesis of Hydrogen Peroxide via Two‐Electron Water Oxidation

“…A peak %FE of 91.5 % for H 2 O 2 production is additionally attained in 5 m K 2 CO 3 , amongst the highest values reported to date for the 2e − WOR (Figure S4). The observations made in this work regarding the influence of high concentrations of K 2 CO 3 on anodic H 2 O 2 production agree with the experimental findings and theoretical predictions made in previous studies, [19,37−40] where it has been proposed that HO . radicals, generated via the 1e − WOR at the surface of BDD, react with CO 3 2− /HCO 3 − in the aqueous electrolyte to form the transient species CO 3 .− [Eq.…”

“…[10][11][12][13][14][15][16][17] Recently, a transition toward carbonate (CO 3 2À )-based solutions, for H 2 O 2 production, has been noticed, and prominent studies have reported increased H 2 O 2 production rates in Na 2 CO 3 , [18] or K 2 CO 3 /KHCO 3 mixtures. [19] A dedicated study on the influence of carbonate electrolytes and their key properties (concentration, pH, conductivity) on H 2 O 2 electrosynthesis via the 2e À WOR has yet to be carried out.…”

“…Highly concentrated hydrogen carbonate, or bicarbonate (HCO 3 − ), solutions have been identified as suitable electrolytes for H 2 O 2 production, [9] with 2 m KHCO 3 being well established in the 2e − WOR literature as the convention for aqueous supporting electrolytes [10–17] . Recently, a transition toward carbonate (CO 3 2− )‐based solutions, for H 2 O 2 production, has been noticed, and prominent studies have reported increased H 2 O 2 production rates in Na 2 CO 3 , [18] or K 2 CO 3 /KHCO 3 mixtures [19] . A dedicated study on the influence of carbonate electrolytes and their key properties (concentration, pH, conductivity) on H 2 O 2 electrosynthesis via the 2e − WOR has yet to be carried out.…”

Future perspectives for the advancement of electrochemical hydrogen peroxide production

“…Acronyms used in material descriptions are taken from the original works. Data taken from references [15,25,34,[38][39][40][41] Figure 2 highlights that the scope of possible materials is incredibly broad and outside the scope of this discussion. A number of excellent reviews are available for more detailed insights specifically into materials development.…”

“…Optimising factors such as doping level and electrolyte composition can address this to give a sizeable increase in faradaic efficiency and production rate. [34] A popular alternative are metal oxides, which give high efficiencies, [35,36] but are usually reported at low current densities (Fig 2C ,D). It is worth noting that it is difficult to compare the activity of many metal oxides to carbon catalysts due to the different surface areas: carbon catalysts tend to be porous whereas metal oxides are often thin films with much lower active areas.…”