Lattice strain engineering enabling nickel sulfide for seawater splitting at high current density

The instability of transition metal sulfides (TMSs) electrocatalysts poses challenges in seawater splitting, particularly in the oxygen evolution reaction (OER). Lattice strain is an effective strategy to enhance the performance of TMSs. In this work, a lattice-strained Ni₃S₂ (NiFeCoS-LS) was synthesized via a facile room-temperature strategy, where the effective incorporation of Fe and Co induces substantial lattice strain that significantly improves the resistance to Cl⁻-induced corrosion during alkaline seawater oxidation. As a result, the NiFeCoS-LS catalyst exhibits exceptional long-term stability, maintaining stable performance for over 300 h at a current density of 0.5 A cm⁻² in alkaline seawater electrolysis. In contrast, the hydrothermally synthesized NiFeCoS (NiFeCoS-HT), which lacks lattice strain, exhibits significantly reduced stability. The enhanced performance arises from the improved thermodynamic stability of Ni₃S₂ induced by lattice strain, which reinforces its structural robustness under operating conditions. Supported by theoretical calculations, the reconstruction and corrosion resistance behavior of NiFeCoS-LS were further elucidated. This work provides mechanistic insights into designing corrosion-resistant TMS-based electrocatalysts for effective seawater electrolysis.