H2S-Treated Nickel Foam Electrocatalyst for Alkaline Water Electrolysis under Industrial Conditions

The development of facile synthesis methods for efficient electrocatalysts plays a crucial role in improving the overall efficiency of alkaline water electrolysis. Here we explore a synthesis route using chemical vapor deposition (CVD) with H₂S gas to enhance the efficiency of nickel foam electrocatalysts. A uniform film consisting of distinctive nanostructures was successfully grown on the surface of nickel foam by sulfiding at 95-145 °C in 3% H₂S/Ar for 1-17 h. Electrochemical performance tests under industrially relevant conditions with 30 wt % KOH at 85 °C tested at 200-500 mA cm^-2 for up to 2 weeks showed a reduction in cell voltage up to 0.4 V for modified electrodes, corresponding to 18% higher efficiency for overall water splitting, as compared to pristine nickel foam. Surface area analysis showed a 30-fold increase in the surface area following H₂S treatment. Structural and compositional analyses of the modified nickel foam electrodes were conducted using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), energy dispersive X-ray (EDX) analysis and synchrotron powder X-ray diffraction (XRD). The analysis revealed the presence of Ni₃S₂ with a film thickness of 1-4 μm after the H₂S treatment. Extended reaction times showed continuous reaction and the emergence of NiS. All analyses were performed before and after alkaline water electrolysis. Post-electrolysis characterizations indicated either the absence or minimal presence of sulfur. This suggests that the enhanced performance is likely not attributed to sulfur catalytic activity but rather to alterations in the surface morphology of the nickel foam.