Enhanced Electrocatalytic Performance for Overall Water Splitting: Exploring Heterojunctions and Vacancy-Engineered Nanosheets

This study presents a novel approach to enhance electrocatalytic performance for overall water splitting (OWS) through the strategic construction of distinct catalytic structures. We propose an in-situ transformation method that partly converts ultrathin two-dimensional zeolitic imidazolate framework (ZIF-67) nanosheets into layered double hydroxide (LDH) nanosheets, resulting in catalysts with tailored properties. The situ construction of 2D ZIF-67/CoNi LDHs heterojunctions with optimizes metal-oxygen bands and oxygen vacancies significantly increases the number of accessible catalytic active sites and enhances charge transport efficiency, the reaction intermediates are more easily adsorbed and desorbed during the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) process. Characterization techniques, including polarization curves, The electrochemical active surface area (EASA) and X-ray photoelectron spectroscopy (XPS), reveal abundant accessible active sites and enhanced charge/mass transfer capabilities. Notably, the Co/Ni-LZ-24 NTs achieved an overpotential of only 80.50 mV for HER, while Co/Ni-LZ-36 NTs demonstrated the low overpotential of 289.59 mV for OER at a current density of 10 mA cm⁻² in 1.0 M KOH solution. Furthermore, the coupled catalyst system yields an impressive OWS performance, requiring a minimal cell voltage of 1.59 V at the same current density. This work underscores the importance of synergistic design principles in advancing efficient and sustainable OWS technologies.