Synthesis\nof Hydrogen Peroxide in Neutral Media by\nan Iron-Doped Nickel Phosphide Catalyst

The two-electron oxygen reduction reaction (2e<sup>–</sup> ORR) for electrochemical hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) synthesis has drawn much attention due to its eco-friendly, cost-effective,\nand highly efficient properties. Developing catalysts with excellent\nH<sub>2</sub>O<sub>2</sub> production rates and selectivity is still\na big challenge. In this work, an iron-doped nickel phosphide (Fe-Ni-P)\ncatalyst was synthesized by a solvent thermal method. The synthesis\ntemperature of 180 °C could obtain the best 2e<sup>–</sup> ORR catalyst, i.e., Fe-Ni-P-180, since the crystallization of metal\nphosphide under this temperature was promoted. In addition, Fe-Ni-P-180\nhad a high catalytic activity, high electron transfer rate, and low\nelectrochemical resistance. The H<sub>2</sub>O<sub>2</sub> production\nrate constant of Fe-Ni-P-180 was 9.99 ± 0.63 μM/(min cm<sup>2</sup>) and the Faradaic efficiency was 94.38 ± 4.68% at 0.25\nV vs RHE, which increased by 57.9 and 15.4% compared with Ni–P,\nrespectively. Fe-Ni-P-180 could work in a wide pH range of 5–9\nwith the optimized pH of 7, and it exhibited low specific energy consumption\nand great reusability. The elemental state analysis demonstrated that\nNi<sup>δ+</sup>, Fe<sup>δ+</sup>, and P<sup>δ−</sup> are all active species, and the doping of Fe increases the crystallization\nof metal phosphide.