Layered Double Hydroxide Templated Synthesis of Amorphous NiCoFeB as a Multifunctional Electrocatalyst for Overall Water Splitting and Rechargeable Zinc–Air Batteries

Layered double hydroxides (LDHs) stand out as versatile structural platforms for modulating the electronic structure of highly reactive earth-abundant transition metal-based electrocatalysts for the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and the oxygen reduction reaction (ORR). Herein, a Ni-Co-Fe LDH, electrodeposited on a Ni nanocones (NiNCs)-decorated Ni foam, acts as a morphology driving template to direct the facile constant potential electrosynthesis of NiCoFeB from a K2B4O7 solution. The amorphous tri-metal borate (TMB) displays excellent trifunctional electrocatalytic activities toward the HER (overpotential at 10 mA cm−2, η10 = 174 mV vs RHE), OER (η10 = 208 mV), as well as ORR (half-wave potential = 0.723 V) with a low ΔEOER−ORR of 770 mV, and excellent durability of over 110 h in alkaline solutions. A zinc–air battery based on the TMB@NiNC dual oxygen catalyst cathode exhibits a high open-circuit voltage of 1.477 V, a power density of 107 mW cm−2, a specific energy of 918 W h kgZn−1 and an outstanding cycling stability of over 1330 cycles at 10 mA cm−2, which outperforms the commercial noble metal benchmarks. These results demonstrate that LDHs are efficient sacrificial templates for the preparation of high-performance multifunctional multi-metal borate electrocatalysts for energy-related applications.