Amorphous Bimetallic Phosphate–Carbon Precatalyst with Deep Self-Reconstruction toward Efficient Oxygen Evolution Reaction and Zn–Air Batteries

Abstract

Amorphous transition-metal compounds (a-TMC) have attracted more and more attention due to their high electrocatalytic activity for the oxygen evolution reaction (OER). However, it is still a challenge to in situ synthesize a-TMC-carbon nanocomposites at elevated temperature and figure out the exact advantages of the amorphous structure. Here, an amorphous iron-doped nickel phosphate–carbon hollow nanocomposite (a-NiFePO-C) has been simply prepared by coprecipitation of metal ions and phytic acid, followed by a controllable annealing process. The results show that a-NiFePO-C can achieve a low overpotential of 268 mV at 10 mA/cm2 and maintain 91.3% of the initial current density after a 9 h chronoamperometry test in a 1 M KOH solution with low mass loading of 0.1 mg/cm2. The excellent performance of a-NiFePO-C is attributed to the low charge-transfer resistance, bulk self-reconstruction, and synergetic oxidation of the bimetallic sites during cyclic voltammetry (CV) activation, resulting in the formation of a highly OER-active Fe­(III)-Ni­(oxy)­hydroxide-carbon nanocomposite. Moreover, the rechargeable Zn–air batteries powered by the a-NiFePO-C + Pt/C electrode can present a lower charging voltage and superior cycle performance than that powered by a commercial RuO2 + Pt/C electrode.

Fast and Deep Reconstruction of Coprecipitated Fe Phosphates on Nickel Foams for an Alkaline Oxygen Evolution Reaction

“…This can be attributed to the aggregation of the precatalysts during annealing, which hinders the reconstruction of the samples to form NiFe–OOH nanosheets, thus reducing the exposure of more active area. Similar to the C dl , the electrochemical impedance spectroscopy (EIS) indicates that the annealing can enhance the electrical conductivity of electrocatalysts after reconstruction (Figure e and Table S2), consistent with literature results . Therefore, the high OER activity of NiFe–OOH/NF-4h can be ascribed to the optimal morphology with rich nanosheets and reasonable charge-transfer resistance for the reaction.…”

“…Similar to the C dl , the electrochemical impedance spectroscopy (EIS) indicates that the annealing can enhance the electrical conductivity of electrocatalysts after reconstruction (Figure 3e and Table S2), consistent with literature results. 33 Therefore, the high OER activity of NiFe−OOH/NF-4h can be ascribed to the optimal morphology with rich nanosheets and reasonable chargetransfer resistance for the reaction. Long-term durability is another important parameter to evaluate the electrochemical performance, which is tested at a voltage of 1.52 V vs RHE for NiFe−OOH/NF-4h.…”

Design of earth‐abundant amorphous transition metal‐based catalysts for electrooxidation of small molecules: Advances and perspectives

“…The structure reconstruction of amorphous TM oxometallates/carbon hybrids has been examined on the amorphous Fe-doped Ni phosphate-carbon nanohybrid (a-NiFePO-C). 215 Compared with its crystalline counterpart, the higher OER activities of a-NiFePO-C are due to its more complete self-reconstruction induced highly electroactive Fe(III)-NiOOH-carbon structures (Figure 13C), and low charge-transfer resistance.…”

Carbon-Based Electrocatalyst Design with Phytic Acid—A Versatile Biomass-Derived Modifier of Functional Materials

“…PA primarily serves as a carbon source [ 44 ], although during the carbonization process it also plays the role of a porogen [ 23 , 49 , 65 , 89 ] and phosphorus dopant [ 46 , 54 ] owing to its numerous phosphate groups.…”

“…At neutral pH, PA can form complexes with multivalent metal ions, such as calcium, zinc, or iron [ 42 , 43 ]. Therefore, upon carbonization, it can generate materials simultaneously that are doped with phosphorus and metal (e.g., Fe [ 20 , 44 ], Co [ 45 ], Ni [ 46 ], Sn [ 47 ], Al [ 48 ], Mn [ 49 ]). The six phosphate groups exhibit strong affinity for amino groups through ionic interactions or hydrogen bonds, enabling PA to serve as a crosslinking agent [ 50 , 51 ].…”