Plasma-Engineered 2D Ni Nanoplates as Advanced Oxygen Evolution Reaction Electrocatalysts for Direct Seawater Electrolysis

Abstract

Hydrogen is crucial for achieving carbon neutrality and sustainable energy. To commercialize water electrolysis technology, the development of high-performance OER catalysts is essential. This study utilizes seawater as an electrolyte to enhance economic viability and employs Ni-based materials instead of precious metals like RuO₂. Ni-based Hofmann-type coordination polymers were synthesized via plasma engineering and transformed into 2D Ni nanoplates through thermal treatment. These nanoplates demonstrated exceptional OER performance in both alkaline and alkaline seawater electrolytes, achieving lower overpotentials compared to that of RuO₂. In situ Raman spectroscopy revealed that seawater’s diverse cations and anions increased the disorder of the active phase (NiOOH) through intercalation, suppressing Ni oxidation and active oxygen formation, which reduced OER activity. In an anion exchange membrane water electrolyzer (AEMWE) under alkaline seawater, Ni nanoplates exhibited much lower cell voltages of 267 and 393 mV at current densities of 500 and 1000 mA cm^–2, respectively, compared to RuO₂. Notably, the cell voltage showed negligible changes over 90 h during a durability test at 100 mA cm^–2. This work highlights Ni-based Hofmann-type coordination polymers and their derivatives as efficient OER catalysts for hydrogen generation.