Unraveling Activation Energy with Temperature-Dependent Analyses of CoNiSe<sub>2</sub> Electrocatalysts Derived from CoNi-LDH for Water Splitting Reaction
Ragunath Madhu, Jaisakthi Muthukumar, Preethi Arunachalam, Pradeep Gudlur, Subrata Kundu
Abstract
Developing highly efficient bifunctional electrocatalysts made from abundant metals is key to unlocking the large-scale, sustainable production of hydrogen through water splitting. LDH (layered double hydroxide) materials (thanks to the layered structure and the high surface area) are hot for electrocatalysis due to their unique electron transport properties. Here, in this work, we report the formation of CoNi-LDH-derived CoNiSe 2 nanosheets via a simple hydrothermal technique subjected to water electrolysis in 1 M KOH. The CoNiSe 2 demands a lesser overpotential of 295 and 214 mV in alkaline conditions to reach the 50 mA cm –2 current density toward OER and HER, respectively. Moreover, after selenization, the charge accumulated and surface-active sites are hiked ∼23.6- and 29-fold than the pristine CoNiSe 2, respectively. Likely, high performance is owing to the repulsion between the metal d-band center and the 3p orbitals of Se and the adsorbed O atom (associated O p-band centers). Furthermore, CoNiSe 2 exhibits higher TOF values of 0.3939 and 0.7662 × 10 –3 s –1 toward the OER and HER process, respectively. In addition, a temperature-dependent study demonstrates that selenization reduces the activation energy ( E a ) twice (13.37 kJ/mol) compared to the bare LDH (22.86 kJ/mol). The two-electrode system exhibits 1.635 V as the total cell voltage to reach the benchmarking 10 mA cm –2 current density with a long-term durability of 54 h. The layered structure and subsequent selenization, providing more electrical conductivity toward the water-splitting process, are the reasons for the observed better activity. Overall, this study provides a general strategy toward the synthesis and determination of activation energy toward the water water-splitting process.