Single‐Step Solid‐State Scalable Transformation of Ni‐Based Substrates to High‐Oxidation State Nickel Sulfide Nanoplate Arrays as Exceptional Bifunctional Electrocatalyst for Overall Water Splitting

Abstract

Hydrogen, undoubtedly the next‐generation fuel for supplying the world's energy demands, needs economically scalable bifunctional electrocatalysts for its sustainable production. Non‐noble transition metal‐based electrocatalysts are considered an economic solution for water splitting applications. A single‐step solid‐state approach for the economically scalable transformation of Ni‐based substrates into single‐crystalline nickel sulfide nanoplate arrays is developed. X‐ray diffraction and transmission electron microscopy measurements reveal the influence of the transformation temperature on the crystal growth direction, which in turn can manipulate the chemical state at the catalyst surface. Ni‐based sulfide formed at 450 °C exhibits an enhanced concentration of electrocatalytically‐active Ni3+ at their surface and a reduced electron density around sulfur atoms, optimal for efficient H2 production. The Ni‐based sulfide electrocatalysts display exceptional electrocatalytic performance for both oxygen and hydrogen evolution, with overpotentials of 170 and 90 mV respectively. Remarkably, the two‐electrode cell for overall electrolysis of alkaline water demonstrates an ultra‐low cell potential of 1.46 V at 10 mA cm−2 and 1.69 V at 100 mA cm−2. In addition to the exceptionally low water‐splitting cell voltage, this self‐standing electrocatalyst is of binderfree nature, with the electrode preparation being a low‐cost and single‐step process, easily scalable to industrial scales.

Enabling Unprecedented Ultra‐Efficient Practical Direct Seawater Splitting by Finely‐Tuned Catalyst Environment via Thermo‐Hydrodynamic Modulation

“…The choice of the electrocatalyst was based on previous literature reports, where earth-abundant nickel-based materials were successfully demonstrated as effective bifunctional catalysts for overall water splitting. [21,41] Thus, Ni foil substrates were transformed into electrocatalytic, binder-free electrodes via a welloptimized single-step transformation process, as detailed in the experimental section. The NiS 2 pS x surface catalyst is prepared by the direct in situ transformation of Ni foil under elemental sulfur environments in the ratio (2:1).…”

MnOx-decorated MOF-derived nickel–cobalt bimetallic phosphide nanosheet arrays for overall water splitting

“…Although their HER and OER performances are excellent, their large-scale industrial application is greatly limited by their inherent scarcity and high costs. 6,7 To address these challenges, a variety of cost-effective transition metal-based electrocatalysts with favourable activity for the OER or HER, such as metal oxides, 8,9 sulfides, 10,11 selenides, 12,13 nitrides 14,15 and phosphides, 16,17 have been developed. Dual-functional catalysts capable of catalyzing both the HER and the OER simultaneously are being explored to simplify the water splitting systems.…”

Magnetic Field-Assisted Electrodeposition of Fe3O4 Nanoparticles on Ni as Bifunctional Electrocatalyst for Overall Water Splitting

“…Transition metal chemicals (TMCs) have been widely used in research as catalysts targeting HER/OER due to their abundant resource storage, low cost, and environmental friendliness, especially nickel-based materials. − However, it was found that their low intrinsic conductivity is a huge obstacle to overcome to replace the precious metal HER/OER catalysts, . Nowadays, the main methods for the preparation of Ni-based catalysts are the hydrothermal method, the sol–gel method, the vapor-phase deposition method, the chemical method, and the electrodeposition method. , The hydrothermal method requires more stringent preparation conditions.…”