Hierarchical 3D-nanoflower LDHs Heterojunction: A Bifunctional Electrocatalyst for Total Water Splitting

Abstract

Hydrogen is a clean energy alternative to conventional hydrocarbons in various applications. Water electrolysis is the fastest and most efficient approach for generating pure hydrogen with zero carbon emissions. Layered double hydroxide (LDHs) is the most prominent material for developing efficient and cost-effective electrocatalysts for water splitting. A highly efficient approach for designing an electrocatalyst with improved performance is to develop a hierarchical LDHs heterojunction with a modulating electronic structure. In this work, we designed a hierarchical NiFe-LDH/NiCo-LDHs heterostructure over Ni foam via a hydrothermal process, which exhibits enhanced OER and HER performance in alkaline conditions. Additionally, the heterostructure shows a high faradaic efficiency value of 93.4% at 1.65 V potential, demonstrating excellent selectivity toward electrocatalytic reaction. Furthermore, the prolonged stability over 60 h at 1.55 V highlights its sturdiness. The prepared catalyst exhibits TOF value (0.155 sec-1) that is 13 and 24 times greater than that of NiFe-LDH (0.0125 sec-1) and NiCo-LDH (0.0063 sec-1), respectively, towards OER. The pH-dependent study reveals that the NiFe-LDH/NiCo-LDH heterostructure follows the Adsorbate enhancement mechanism (AEM) rather than the lattice oxygen mechanism (LOM). DFT studies further confirm the synergistic interaction in the NiFe-LDH/NiCo-LDH interface which facilitates the enhanced activity in OER, whereas in HER the reduction in 〖∆G〗_H^* value which increases the adsorption and desorption process of H atom over the catalyst. This work offers a new route for improving electrocatalytic performance by developing the hierarchical LDHs heterojunction.