Ultrathin 2D metal-organic framework nanosheet arrays to boost the overall efficiency of water splitting

Developing cost-effective and highly efficient electrocatalysts for water splitting has posed a significant challenge in recent research. This work presents a facile approach to synthesizing a 2D nickel-based metal-organic framework (TIT-1) using 2,3,5,6-tetracarboxyphenylpyrimidine (TCPP), 4,4′-bipyridine (BPY) and nickel nitrate hexahydrate under solvothermal conditions. The detailed structure and phase purity were characterized by X-ray analysis, X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). To enhance the water electrolysis ability, the TIT-1 nanosheet (TIT-1@NS/NF) was fabricated via ultrasonic treatment of pure TIT-1 for 30 min. The TIT-1@NS/NF electrode was synthesized via an in-situ growth method and employed as an electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at ambient temperature. The results indicate that TIT-1@NS/NF achieved a current density of 10 mA cm−2 at an overpotential of 196 mV for OER and 270 mV for HER under the same conditions, so exhibiting superior performance compared to TIT-1. The electrochemical durability of TIT-1@NS/NF showed a retention rate of 87% for OER and 90% for HER. The superior electrocatalytic performance is primarily attribute to the synergistic impact of the 2D nanosheet architecture, which significantly increased the specific surface area and facilitated enhances electronic conductivity. The presence of partially deprotonated carboxylate groups and open metal sites (OMS) in TIT-1 further boosts the enhanced activity, as they exposed a multitude of unsaturated metal sites, thereby optimizing both the OER and HER process. Additionally, an asymmetric electrolytic cell comprising TIT-1@NS/NF was designed and assembled to assess its effectiveness for overall water splitting in alkaline conditions.