Rapid and scalable electrosynthesis of high-concentration hydrogen peroxide in neutral media over s-block metal single-site catalysts

Activation of Inert Mg Sites for 2e − ORR Electrocatalysis The π-π interaction between hydroxyl-functionalized carbon nanotubes and Mg phthalocyanine induces an electron-rich structure in the Mg center, optimizing and strengthening the adsorption of ORR intermediates on Mg center, thereby significantly enhancing their 2e − ORR activity and selectivity. Meanwhile, the naturally stable valence state and weak hydrogen adsorption capability of Mg ensure that the catalyst maintains steady 2e − ORR performance at high current densities and H 2 O 2 concentrations, preventing the Fenton reaction from converting H 2 O 2 into hydroxyl radicals (·OH). This effectively ensures industrial-grade H 2 O 2 production with high concentration, current density, and selectivity. • Efficient H 2 O 2 Synthesis and High Economic Viability in Neutral Conditions In a flow cell system, the MgPc/CNT-OH catalyst achieves a Faradaic efficiency (FE) of over 90% at a current density of 500 mA cm −2 . Operating at 400 mA cm −2 , the catalyst sustains stable performance for 50 h with FE of above 90%. Techno-economic analysis reveals that the production cost is significantly lower than the market price at electricity prices ranging from 3 to 9 cents/kWh, confirming its economic feasibility for industrial-scale production. • Ampere-Level Current Electrosynthesis, High-Concentration Product, and Diverse Practical Applications The MgPc/CNT-OH catalyst maintains an FE of over 80% when operating at currents ranging from 0.5 to 20 A in a 100 cm 2 flow cell system. Following a 25-h stability test at 10 A, the catalyst maintained an FE of 85.9% with a H 2 O 2 concentration of 1.82 wt%. By adjusting the flow rate, the electrosynthesized H 2 O 2 concentration reached 8.17 wt%, outperforming currently reported catalysts. The synthesized 8.17 wt% H 2 O 2 was directly extracted into solid sodium percarbonate with virtually no impurities. Antibacterial experiments further demonstrated its potential for diverse applications. Through a molecular modulation strategy, this work achieves significant progress in the efficient electrochemical synthesis of H 2 O 2 with high concentration and selectivity, holding clear implications for sustainable green electrochemistry and environmental fields. We believe these findings will be of great interest to the broad readership of Chemical Engineering Journal and fall well within its scope covering chemical synthesis and electrocatalysis. Below I list some of the representative works published in top-tier journals for comparison. The two-electron oxygen reduction reaction (2e − ORR) emerges as a sustainable route for on-site hydrogen peroxide (H 2 O 2 ) production, and the industrial electrosynthesis of high-concentration H 2 O 2 holds tremendous practical and application value. However, conventional transition-metal catalysts suffer from a critical limitation in the 2e − ORR process, where maintaining high H 2 O 2 selectivity under high H 2 O 2 concentrations remains a formidable challenge. Specifically, under high current densities with low reduction potentials, typical transition metals with variable valence states readily induce Fenton reactions, competitive 4e − ORR, and hydrogen evolution reactions, restricting high-concentration H 2 O 2 generation. To address these, we report a single-site s -block main-group metal electrocatalyst consisting of magnesium phthalocyanine supported on hydroxyl-functionalized carbon nanotubes (MgPc/CNT-OH). The s -block Mg center possesses stable valence and weak hydrogen adsorption, inhibiting Fenton and hydrogen evolution, while the hydroxyl species on the carbon support interacts electronically with Mg sites and optimizes ORR intermediate adsorption. Accordingly, the catalyst delivers ~90% Faradaic efficiency at 400 mA cm −2 . In a 100 cm 2 flow cell, it operates stably for 25 h at 10 A, producing 1.82 wt% H 2 O 2 , which can be increased to 8.17 wt% by adjusting electrolyte flow rates. Techno-economic analysis verifies the superior cost-competitiveness of this system over commercial H 2 O 2 production. Hydroxylated carbon nanotubes optimize the adsorption energy between the phthalocyanine-centered Mg sites and *OOH intermediates, thereby promoting highly selective and active hydrogen peroxide production. Meanwhile, the s -block metal sites effectively suppress the competing hydrogen evolution reaction (HER) and Fenton reactions. Download: Download high-res image (154KB) Download: Download full-size image