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

Abstract

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 O₂ 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 O₂ 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 O₂ under water, in sharp contrast to the difficult O₂ 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 g_cat^–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 O₂ 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.