Durable and Selective Electrochemical H2O2 Synthesis under a Large Current Enabled by the Cathode with Highly Hydrophobic Three-Phase Architecture

Hydrogen peroxide (H2O2) synthesis by electrochemical two-electron oxygen reduction has garnered increasing interest as an attractive alternative to the industrial anthraquinone process. However, the electrochemical H2O2 synthesis suffers a low current efficiency due to O-2 diffusion restriction when performing at a large current, which would be further aggravated by the electrode flooding issue. Here, we present a highly hydrophobic gas-liquid-solid three-phase architecture consisting of densely distributed N-doped carbon (NPC) nanopolyhedra, which presents the superaerophilicity feature to achieve rapid gaseous O-2 transport and trap even under high-current operation by virtue of electrolyte-flooding resistibility. The aerophilicity of the hydrophobic NPC architecture is visibly verified by the rapid trapping for gaseous O-2 under water, in sharp contrast to the difficult O-2 capture by the hydrophilic NPC surface. Using the aerophilic three-phase NPC architecture, it can deliver a current of 50-250 mA cm(-2) with an 83-99% current efficiency, achieving an 8.53 mol gcat(-1)h(-)(1) H2O2 production rate (at 100 mA cm(-2)), which makes it possible to manufacture high-concentration H2O2 (0.66-5.38 wt %). The high hydrophobicity feature of the three- phase NPC architecture endows the flood-proof ability that guarantees unblocked O-2 transport and trapping, thus enabling the durability for 200 h electrocatalytic H2O2 synthesis at 100 mA cm(-2) that largely outperforms its hydrophilic NPC counterparts. This H2O2 electrosynthesis technology presents attractive potential in practical application, as demonstrated by the less expensive IrO2/Ti mesh anode construction, low electricity demand (0.15-0.43 kWh per kg 3 wt % H2O2), and facile scale-up of device. This work presents a highly selective, durable, and low-cost H2O2 electrosynthesis, providing a promising approach for the in situ H2O2 production and utilization.

Automated summary

A highly hydrophobic gas-liquid-solid three-phase architecture has been proposed to improve the electrochemical synthesis of H2O2, achieving high efficiency and high concentration of H2O2 production.