We report on our recent finding here that bimetallic nickel–cobalt sulfide nanosheet arrays on carbon cloth (NiCo2S4 NS/CC) by anion exchange from its NiCo-precursor could act as a flexible, versatile and fabulous electrocatalyst for both the overall water splitting and urea electrolysis in base. The overall water-splitting efficiency of this material is higher than that for reported NiCo2S4 nanowire array on CC with just needing a voltage of 1.66 V to afford 10 mA cm–2. Moreover, this material also shows fabulous catalytic activity and selectivity for urea oxidation reaction (UOR) with an ultralow potential of 0.249 V vs SCE to obtain 10 mA cm–2, surpassing all reported transition-metal based UOR catalysts. An urea-assisted energy-saving alkaline hydrogen-production system was further built here by replacing anodic oxygen evolution reaction with UOR. This whole urea-electrolysis cell driven by NiCo2S4 NS/CC (+,−) affords 10 mA cm–2 at a relative low voltage of 1.49 V, which is 210 mV less than that for u...