Ultrafast fabrication of nickel sulfide film on Ni foam for efficient overall water splitting

Abstract

Development of low-cost, high performance and stable non-noble electrocatalysts with both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities for overall water splitting is essential for future energy supply. Herein, for the first time, a facile and ultrafast synthetic method has been reported to fabricate nickel sulfide (Ni3S2) films on Ni foam (Ni3S2/NF) as efficient bifunctional electrodes for overall water splitting through direct dropping of mercaptoethanol solution followed by annealing at 300 °C for only 50 s. Thanks to the integrated three-dimensional (3D) configuration, the obtained Ni3S2/Ni foam exhibits excellent activity and stability for HER and OER with low overpotentials of 131 and 312 mV, respectively, to attain a current density of 10 mA cm-2 in alkaline media. Ni(OH)x species formed on the Ni3S2 surface serves as the actual catalytic site during OER reaction. Given the well-defined bifunctionality, an overall water-splitting device using two identical Ni3S2/NF electrodes delivers a current density of 10 mA cm-2 at a low cell voltage of 1.68 V in an alkaline water electrolyzer. This approach is promising as a simple method for depositing a wide range of useful transition metal sulfide electrocatalysts on corresponding metal substrate bifunctional electrodes for overall water splitting, shedding some light on the development of functional materials in energy chemistry.

Electrochemically Fabricated Ni−P, Ni−S and Ni−Se Materials for Overall Water Splitting: Investigating the Concept of Bifunctional Electrocatalysis

“…[1i,33] Interestingly, there is no evidence of oxidation into phosphate surface species upon exposure to atmosphere as there is no peak present at 134 eV. [33a] After the OER, there are some significant chemical changes whereby the peak at 852.5 eV disappears due to the conversion of metallic Ni to oxides or hydroxides (Figure 6b4), [12] with also evidence of NiOOH formation as indicated by a peak at 855.7 eV. [23] The P 2p doublet peak at 130 eV decreased dramatically in intensity (Figure 6b5) with the emergence of a peak at around 133 eV which is attributed to phosphate formation, [34] or oxidized species of P. [1p,15] This appears to be in slight contradiction to another study by Stern et al [35] who demonstrated the formation of a core-shell Ni 2 P/NiO x structure as the active form for the OER which is generated in-situ from Ni 2 P during the OER, but with no evidence of phosphate species retained on the surface.…”

“…Very recently Ren et al . reported the bifunctionality of Ni foam after converting the surface into Ni 3 S 2 . However after post OER analysis, they postulated that the amorphous Ni(OH) x formed on the surface was the active species for the OER.…”

“…[11] Very recently Ren et al reported the bifunctionality of Ni foam after converting the surface into Ni 3 S 2 . [12] However after post OER analysis, they postulated that the amorphous Ni(OH) x formed on the surface was the active species for the OER. In addition, there was a clear depletion of sulfur but not complete removal which may also impact on the electrocatalytic activity.…”

Rapid Fabrication of Ni/NiO@CoFe Layered Double Hydroxide Hierarchical Nanostructures by Femtosecond Laser Ablation and Electrodeposition for Efficient Overall Water Splitting

“…However, most of the preparation methods require high‐temperature annealing treatments and long hydrothermal reactions, which are complicated, time‐consuming, and energy‐intensive. Moreover, some of the preparation processes, such as sulfuration and phosphorization, often involve toxic sulfur‐ or phosphorus‐containing gases . In addition, traditional electrode preparation techniques require the powder catalysts to be adhered to conducting substrates by using a polymer binder, such as Nafion, which often affects the stability of the catalysts and leads to “dead volume” .…”

MoFe‐Codoped Ni3S2/Ni(OH)2 Nanosheets with Large Sample Size toward High‐Performance Oxygen Evolution

“…Therefore, efficient, stable, and large‐scaled OER electrocatalysts are highly essential for the overall water splitting. To replace the benchmark OER catalyst of IrO 2 or RuO 2 , the first‐row transition metals such as Ni‐based sulfides, hydroxides, oxy‐hydroxides, and nitrides have been extensively studied due to the low cost, earth abundance, and low‐temperature synthesis. However, the low overpotential and high stability still remain a great challenge toward OER.…”