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Searching for efficient, stable and low-cost nonprecious catalysts for oxygen and hydrogen evolution reactions (OER and HER) is highly desired in overall water splitting (OWS). Herein, presented is a nickel foam (NF)-supported MoS 2 /NiFeS 2 heterostructure, as an efficient electrocatalyst for OER, HER and OWS. The MoS 2 /NiFeS 2 /NF catalyst achieves a 500 mA cm−2 current density at a small overpotential of 303 mV for OER, and 228 mV for HER. Assembled as an electrolyzer for OWS, such a MoS 2 /NiFeS 2 /NF heterostructure catalyst shows a quite low cell voltage (≈1.79 V) at 500 mA cm−2, which is among the best values of current non-noble metal electrocatalysts. Even at the extremely large current density of 1000 mA cm−2, the MoS 2 /NiFeS 2 /NF catalyst presents low overpotentials of 314 and 253 mV for OER and HER, respectively. Furthermore, MoS 2 /NiFeS 2 /NF shows a ceaseless durability over 25 h with almost no change in the cell voltage. The superior catalytic activity and stability at large current densities (>500 mA cm−2) far exceed the benchmark RuO 2 and Pt/C catalysts. This work sheds a new light on the development of highly active and stable nonprecious electrocatalysts for industrial water electrolysis. [Display omitted] • MoS 2 /NiFeS 2 /NF shows ultrahigh activity for OER and HER at large current density. • Ultralow overpotentials (η 1000, OER = 314 mV, η 1000, HER = 254 mV) are needed. • MoS 2 /NiFeS 2 /NF exhibits ultralow cell voltage of 1.79 V@500 mA/cm2 for OWS. • The catalyst shows high stability with no decay in the CP test for OWS over 25 h. [ABSTRACT FROM AUTHOR]

Hydrogen, carrying a high energy density and emitting zero greenhouse gases when in use, is particularly promising as an alternative for traditional fossil fuels. Electrochemical water splitting is an economical technology for producing sustainable and high-purity hydrogen gas. However, the intrinsically sluggish kinetics of the anode oxygen evolution reaction (OER) always decreases the efficiency of hydrogen production; the development of highly active and durable electrocatalysts with improved OER kinetics is thus desirable and crucial. Herein, Fe-based metal–organic framework (MOF)-Ni3S2 heterostructure nanocomposites are synthesized on a nickel foam (NF) substrate. The self-supporting Fe MOF-Ni3S2/NF catalyst shows excellent catalytic activities for OER. In alkaline media (1.0 M KOH), only 243 mV of overpotential is needed to reach the current density of 100 mA·cm–2. Even at the commercially viable high current densities of 500 and 1000 mA·cm–2, ultralow overpotentials of 283 and 309 mV are required, respectively. The catalytic activity of Fe MOF-Ni3S2/NF far exceeds that of the noble metal catalysts (e.g., RuO2) and most non-noble metal OER catalysts reported in the literature. In addition, the Fe MOF-Ni3S2/NF nanocomposite exhibits ultrahigh long-term stability at high current densities, with almost no activity attenuation in the chronopotentiometry test conducted at 100 mA·cm–2 and a negligible attenuation (23 mV) at 500 mA·cm–2 for 20 h. Our findings provide insights into designing and preparing cost-effective, highly active, and durable electrocatalysts for OER at high current densities. [ABSTRACT FROM AUTHOR]

Summary: Ultrathin FeNiOxHy nanoflake arrays with the thickness of only ~4.5 nm were prepared on Ni foam (NF) via a facile hydrothermal reaction. The oxygen evolution reaction (OER) properties of the obtained sample (FeNiOxHy/NF) were investigated under alkaline conditions (1.0 M KOH). The optimized FeNiOxHy/NF displays extremely small overpotentials of only 195 and 306 mV to achieve the current densities of 10 and 1000 mA cm−2, respectively, and shows almost no potential attenuation during the 160 hours of stability test even the current density is up to 1000 mA cm−2, demonstrating brilliant OER catalytic activity and durability. FeOOH and the NiOOH produced from the in situ oxidation of the surface Ni atoms of the NF substrate are the active sites. The synergistic effect between FeOOH and NiOOH is responsible for the high performances. To our knowledge, the high activity and stability of FeNiOxHy/NF catalyst outperform almost all of the OER catalysts reported to date. These informative findings are valuable not only for understanding the mechanism of OER but also for the design of cheap transition metal catalysts for industrial water electrolysis at high current densities. [ABSTRACT FROM AUTHOR]

Water electrolysis is an efficient approach for high-purity hydrogen production. However, the anodic sluggish oxygen evolution reaction (OER) always needs high overpotential and thus brings about superfluous electricity cost of water electrolysis. Therefore, exploiting highly efficient OER electrocatalysts with small overpotential especially at high current density will undoubtedly boost the development of industrial water electrolysis. Herein, we used a simple hydrothermal method to prepare a novel FeOOH–CoS nanocomposite on nickel foam (NF). The as-prepared FeOOH–CoS/NF catalyst displays an excellent OER performance with extremely low overpotentials of 306 and 329 mV at 500 and 1000 mA cm−2 in 1.0 M KOH, respectively. In addition, the FeOOH–CoS/NF catalyst can maintain excellent catalytic stability for more than 50 h, and the OER catalytic activity shows almost no attenuation no matter after 1000 repeated CV cycles or 50 h of stability test. The high catalytic activity and stability have exceeded most non-noble metal electrocatalysts reported in literature, which makes the FeOOH–CoS/NF composite catalyst have promising applications in the industrial water electrolysis. • Nickel foam (NF) supported FeOOH–CoS composite electrocatalyst is synthesized. • FeOOH–CoS/NF shows extremely low overpotential of OER at high current density. • FeOOH–CoS/NF can maintain excellent catalytic stability for more than 50 h. • Our work provides new insights in preparing non-noble metal OER catalysts. [ABSTRACT FROM AUTHOR]

The main energy consumption of industrial water electrolysis is electric energy, which accounts for ca. 80% of the total cost of water electrolysis. Developing highly efficient bifunctional electrocatalyst for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is essential to reduce the energy consumption. Herein, nickel foam (NF)-supported NiCoP nanorod array catalyst is prepared and used for HER and OER. Not only at a small current density (10 mA/cm2), but also at the commercially required high current density (≥500 mA/cm2), NiCoP/NF catalyst shows excellent bifunctional properties with extremely low overpotential and high stability. Small overpotentials of 60 and 253 mV are needed to drive the current density of 10 mA/cm2 for HER and OER, respectively, and the cell voltage of overall water splitting is only 1.55 V. At the high current density of 500 mA/cm2, the overpotentials are 180 and 365 mV, and the corresponding cell voltage is only 1.83 V. Furthermore, the cell voltage hardly changes within 24 h of overall water splitting test, which makes the catalyst have promising applications in the industrial water electrolysis. The high performance of NiCoP/NF outperforms the commercial RuO 2 -Pt/C couple and most of the bifunctional Ni/Co-based catalysts reported so far. Image 1 • Ni foam-supported NiCoP nanorod array catalyst is prepared and used for HER and OER. • Not only at low but also at high current densities, NiCoP/NF shows high activity. • NiCoP/NF requires only 1.83 V to drive 500 mA/cm2 for overall water splitting. • Hydroxides in-situ formed in the catalytic process contribute to the high activity. [ABSTRACT FROM AUTHOR]