Zirconia on Reduced Graphene Oxide Sheets: Synergistic Catalyst with High Selectivity for H₂O₂ Electrogeneration

Abstract

In situ electrogeneration of hydrogen peroxide through the oxygen reduction reaction (ORR) represents a potentially greener route for wastewater treatment. However, the development of adequate catalysts following a two‐electron pathway with high selectivity and low overpotential is still of great importance. To address this issue, nanoparticles of zirconium oxide supported on reduced graphene oxide (rGO) sheets were prepared through a hydrothermal reaction, and the composite catalysts were tested for the ORR in both acid and alkaline media. The presence of zirconium oxides (ZrO2‐x and ZrO2) significantly improved the activity of rGO for the ORR and its selectivity toward H2O2 electrogeneration. Indeed, an increase from 73.7 to 89.5% was obtained in acid solution, and from 72.9 to 83.1% in alkaline medium. The high activity of the composite catalysts is assigned to the synergistic effect between ZrO2‐x and rGO. The highest selectivity for H2O2 electrogeneration was correlated to the presence of ZrO2 phase. In addition, the zirconia‐rGO catalysts are stable and reusable. Therefore, these composites are very promising catalysts to be used in gas diffusion electrodes for advanced oxidation processes.

Iron‐Containing Nitrogen‐Doped Carbon Nanomaterials Prepared via NaCl Template as Efficient Electrocatalysts for the Oxygen Reduction Reaction

“…The X‐ray diffraction (XRD) analysis of FeNC1 reveals that the catalyst contains small amounts of crystalline Fe and Fe 3 C phases (Figure 2b). The reflections corresponding to ZrO 2 residue are also evident; this originates from ball‐milling procedure and has shown to be rather inactive for ORR [47] …”

“…The reflections corresponding to ZrO 2 residue are also evident; this originates from ball-milling procedure and has shown to be rather inactive for ORR. [47] The investigation of the graphitic and disordered carbon phases in FeNC1 catalyst was carried out by Micro-Raman spectroscopy. As expected for a disordered carbon material, the Raman spectrum shows two first-order bands, D 1 band corresponding to disordered carbon at 1350 cm À 1 and G band related to graphitic carbon at about 1580 cm À 1 (Figure 2c).…”

Engineering of a Low‐Cost, Highly Active, and Durable Tantalate–Graphene Hybrid Electrocatalyst for Oxygen Reduction

“…Oxygen reduction reaction (ORR) is one of the most important reactions in renewable energy conversion of defects such as oxygen vacancies. [12,[19][20][21][22] As illustrated in Table S1, Supporting Information, [16,18,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] the activity of this class of materials is still low, that is, they require high overpotential even to achieve a modest current density, and do not reach the limiting current value expected for the reduction of oxygen to water by the four-electron pathway:…”

“…Oxides from metals belonging to groups 4 and 5 (Ti, V, Zr, Nb, Hf, Ta) have attracted interest in these fields, mainly due to their low cost compared to PGM catalysts, environmental compatibility, and excellent stability in acid medium. [ 12,16–19 ] It has been demonstrated that these oxides can have some activity toward ORR, if their stoichiometry is conveniently tailored to generate a high concentration of defects such as oxygen vacancies. [ 12,19–22 ] As illustrated in Table S1, Supporting Information, [ 16,18,21–35 ] the activity of this class of materials is still low, that is, they require high overpotential even to achieve a modest current density, and do not reach the limiting current value expected for the reduction of oxygen to water by the four‐electron pathway: …”

“…[15] Oxides from metals belonging to groups 4 and 5 (Ti, V, Zr, Nb, Hf, Ta) have attracted interest in these fields, mainly due to their low cost compared to PGM catalysts, environmental compatibility, and excellent stability in acid medium. [12,[16][17][18][19] It has been demonstrated that these oxides can have some activity toward ORR, if their stoichiometry is conveniently tailored to generate a high concentration The oxygen reduction reaction (ORR) is one of the most important reactions in renewable energy conversion and storage devices. The full deployment of these devices depends on the development of highly active, stable, and low-cost catalysts.…”