2D Ni‐Naphthalene‐2,6‐Dicarboxylic Acid Metal‐Organic Framework as Electrocatalysts for Efficient Overall Water Splitting

Abstract

Two‐dimensional metal‐organic frameworks (MOFs) are regarded as promising electrocatalysts because of their high surface area and tunable compositions. Herein, a novel nickel‐based 2D MOF for efficient oxygen evolution reaction (OER) has been developed. Ni‐NDC MOF nanosheets (NDC = naphthalene‐2,6‐dicarboxylic acid) are successfully synthesized on a nickel foam (NF) through a surfactant‐assisted one‐step hydrothermal method. The resulting Ni‐NDC@NF possessing a high electrochemically active surface area of 3.06 mF cm−2 exhibits excellent OER performance with a low overpotential of 249 mV at 10 mA cm−2, a small Tafel slope of 74 mV dec−1, 100% faradaic efficiency, and long‐term stability of 24 h at least. For the application of a bifunctional catalyst, NiMo alloy is electrodeposited on the Ni‐NDC@NF to enhance hydrogen evolution reaction activity. The overall water splitting in a two‐electrode configuration of NiMo/Ni‐NDC@NF electrodes as both anode and cathode require only a 1.56 V for 20 mA cm−2. The photovoltaic‐electrocatalysis system powered by the tandem solar cell represents a high solar‐to‐hydrogen efficiency of ≈22%. This work will contribute to inspiring the design of novel MOF composite catalysts using vertically aligned 2D MOF nanosheet architecture, thereby enlarging the potential of MOFs on next‐generation electrocatalysts and energy devices.