Investigation of seawater electrolyte on hydrogen evolution reaction from the perspective of kinetics and energy consumption using an Ni-based electrocatalyst supported on carbon nanotubes

Abstract

In this study, a Ni-based composite incorporating Ni₄N and La₂O₃ supported on carbon nanotubes (Ni–La–Ni₄N/CNT) was synthesized as an efficiency electrocatalyst towards the hydrogen evolution reaction in different electrolytes with the kinetics and energy consumption investigated in detail. The Ni–La–Ni₄N/CNT exhibits overpotentials of 124 mV and 200 mV at the current density of 10 mA cm⁻² in 1.0 M KOH and alkaline seawater, respectively. As quantitative comparison, the exchange current density (j°) based on Volmer–Heyrovsky–Tafel mechanism was calculated from various polarization curves, which indicated that the addition of NaCl in alkaline medium or using seawater alone reduced the reactivity of the catalyst. The activity of Ni–La–Ni₄N/CNT in alkaline seawater was equal to 91% of that in 1.0 M KOH. Furthermore, dynamic polarization resistance and corresponding current were obtained by the analysis of the equivalent circuit model with the extended Kalman filter algorithm. The analysis of the resistance power at 1 mW also shows that the current between the conditions in KOH and in seawater is 2.76 times. Adding alkaline substances to seawater can narrow it to 1.19 times. These strategies provide novel approaches for inspecting the activity changes of materials in different electrochemical environments.