One-step controllable synthesis of amorphous (Ni-Fe)S /NiFe(OH) hollow microtube/sphere films as superior bifunctional electrocatalysts for quasi-industrial water splitting at large-current-density

Crystalline transition-metal chalcogenides with (oxy)-hydroxides hybrids multiple nanoarchitectures are a new type of promising bifunctional electrocatalysts for electrolysis of water, but their amorphous states are scarcely studied. Herein, a facile electrodeposited approach is presented to fabricate hierarchically amorphous (Ni-Fe)Sx/NiFe(OH)y films on Nickel foam. By accurately tuning multi-components and electrochemical-parameters resulting in abundant micro-tube/sphere morphologies and phase evolution to obtain unique amorphous nano-cluster architectures, the (Ni-Fe)Sx/NiFe(OH)y catalyst performs super electrocatalytic performance, driving the current density of 100 mA·cm−2 at ultralow overpotential of 124 mV and 290 mV for hydrogen and oxygen evolution reaction in 1 M KOH solution with first-class long-term stability for at least 50 h, respectively. In addition, the bimetallic Ni-Fe sulfides and NiFe hydroxides are confirmed to be highly-intrinsic active components for HER and OER. More importantly, the (Ni-Fe)Sx/NiFe(OH)y material directly as cathode and anode electrodes, achieves 10 mA·cm−2 at low electrolytic voltage of 1.46 V in 1 M KOH, even at large current density of 1200 mA·cm-2 only needing 2.2 V as well as super-durability at 1000 mA·cm-2 for 50 h in quasi-industrial conditions. Further experimental results reveal that both temperature and appropriate alkalinity are in favour of reducing the overall hydrolytic overpotential due to accelerating sluggish thermodynamics and dynamics. Parallelly, the bifunctional (Ni-Fe)Sx/NiFe(OH)y electrode is one of the best efficient electrocatalysts in alkaline electrolyte up to now and expected for large-scale industrial water-splitting at large-current-density.