Electrocatalytic Production of H2O2 Using COF Particle Electrodes with Co-Ni Bimetallic Sites

Abstract

Hydrogen peroxide (H₂O₂) is a common and important oxidizing agent, which is widely used in environmental protection fields. In this study, the COF framework catalysts with nickel-cobalt bimetallic sites, Co@phthalocyanine (PcNi) - tetrahydroxybenzene (THB), were synthesized through the hydrothermal method. These catalysts were applied as the particulate electrodes in the electrocatalytic hydrogen peroxide (H₂O₂) generation system. Scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterized the Co@PcNi-THB particle electrodes. Scanning electron microscope (SEM) images showed the Co@PcNi-THB particle electrodes featured the porous structure. The electrochemical active area of Co@PcNi-THB increased to (3.97 µF/cm²), which was 2.39 times higher than that of PcNi-THB catalyst (1.66 µF/cm²). The maximum H₂O₂ yield of 3340 µmol/g was obtained with the addition of Co@PcNi-THB catalyst content of 10 mg, current density of 15 mA/cm², pH 11.03, continuous stirring for 1 h at 200 r/min using a magnetic stirrer, and 0.1 M Na₂SO₄ electrolyte, with an energy consumption (EEC) of 3.201 kWh/kg. The acidic atmosphere, Cl⁻ and NO₃⁻ ions have the inhibitory effect on the H₂O₂ yields. After five cycles of Co@PcNi-THB, the H₂O₂ production decreased to 3153 µmol/g, and the retention ratio of Co in Co@PcNi-THB reduced to 94%. Under the same reaction conditions, the Faraday efficiency (FE) obtained using the gas diffusion electrode (GDE) for the Co@PcNi-THB method was 76.4%, and the hydrogen peroxide yield was 3885 µmol/g. The synergistic Co-Ni effect generated by the introduction of the metal Co enhanced the two-electron Oxygen Reduction Reaction (2e⁻ORR) process. This study provides new insights for designing particle electrodes with bimetallic atomic synergistic effects.

Graphical Abstract