Systematic study of electrochemical performance of nickel iron hydroxide (NiFe(OH)2) electrocatalyst at high current densities in alkaline seawater solutions

Abstract

Renewable energy for green hydrogen production presents a promising avenue for sustainable energy storage. However, the increasing demand for green hydrogen may strain freshwater resources. The direct electrolysis of seawater is considered an alternative, but high anion concentration in seawater poses challenges. This study focuses on testing cost-effective electrocatalysts for the oxygen evolution reaction (OER) to facilitate hydrogen generation from seawater electrolysis. The investigation of electrodeposited nickel-iron hydroxide (NiFe(OH)₂) on a microelectrode in alkaline seawater solutions shows promising results for achieving low overpotentials at high current densities. In alkaline simulated seawater (1 M KOH and 0.5 M NaCl), the electrode exhibited low overpotentials of 278 and 305 mV at 333 K, to reach current densities of 500 and 1000 mA cm⁻², respectively. Furthermore, in alkaline natural seawater, the electrode exhibited low overpotentials of 347 and 382 mV at 333 K, to reach 500 and 1000 mA cm⁻², respectively. To deliver a current density of 2000 mA cm⁻², the catalyst requires overpotentials of only 341 mV in 1 M KOH and 0.5 M NaCl solution and 409 mV in alkaline Absolute Ocean, a standardised seawater solution. Overall, the findings from this study provide a benchmark to contribute to the understanding of an effective, low-cost, easy-to-synthesize OER catalyst for seawater electrolysis, offering a practical solution for hydrogen generation.