Partial Selenization Strategy for Fabrication of Ni0.85Se@NiCr-LDH Heterostructure as an Efficient Bifunctional Electrocatalyst for Overall Water Splitting

Abstract

NiCr-LDH and its partial selenization as Ni_0.85Se@NiCr-LDH heterostructure is established here as an alkaline water electrolyzer for achieving enhanced overall water splitting efficiency. The hydrothermally synthesized optimized batch of Ni_0.85Se@NiCr-LDH is thoroughly characterized to elucidate its structure, morphology, and composition. Compared to pristine NiCr-LDH, the batch of Ni_0.85Se@NiCr-LDH exhibits exceptional alkaline OER and HER activity with low overpotentials of 258 and 85 mV at 10 mA cm⁻², respectively. Besides, Ni_0.85Se@NiCr-LDH also exhibits excellent acidic HER with an overpotential of only 61 mV at 10 mA cm⁻², indicating that Ni_0.85Se@NiCr-LDH can operate effectively across a wide pH range. The excellent electrochemical stability of Ni_0.85Se@NiCr-LDH for 24 h operation is attributed to the formation of a thin layer of SeO_x during OER operation. The role of selenization and the effect of Cr in the LDH lattice toward enhanced electrocatalytic water splitting is discussed. The outstanding OER and HER performances of Ni_0.85Se@NiCr-LDH are attributed to the higher electrochemical active surface area, favorable conditions for adsorption of HER/OER intermediates, low charge transfer resistance, and improved conductivity. The practical application of Ni_0.85Se@NiCr-LDH as a bifunctional electrocatalyst for overall water splitting is reflected from the low cell voltage of 1.548 V at 10 mA cm⁻².