Autogenous Growth of Hierarchical NiFe(OH)_x/FeS Nanosheet‐On‐Microsheet Arrays for Synergistically Enhanced High‐Output Water Oxidation

Abstract

Practical electrochemical water splitting requires cost-effective electrodes capable of steadily working at high output, leading to the challenges for efficient and stable electrodes for the oxygen evolution reaction (OER). Herein, by simply using conductive FeS microsheet arrays vertically pre-grown on iron foam (FeS/IF) as both substrate and source to in situ form vertically aligned NiFe(OH) x nanosheets arrays, a hierarchical electrode with a nano/micro sheet-on-sheet structure (NiFe(OH) x /FeS/IF) can be readily achieved to meet the requirements. Such hierarchical electrode architecture with a superhydrophilic surface also allows for prompt gas release even at high output. As a result, NiFe(OH) x /FeS/IF exhibits superior OER activity with an overpotential of 245 mV at 50 mA cm −2 and can steadily output 1000 mA cm −2 at a low overpotential of 332 mV. The water-alkali electrolyzer using NiFe(OH) x /FeS/IF as the anode can deliver 10 mA cm −2 at 1.50 V and steadily operate at 300 mA cm −2 with a small cell voltage for 70 h. Furthermore, a solar-driven electrolyzer using the developed electrode demonstrates an exceptionally high solarto-hydrogen efficiency of 18.6%. Such performance together with low-cost Fe-based materials and facile mass production suggest the present strategy may open up opportunities for rationally designing hierarchical electrocatalysts for practical water splitting or diverse applications.

NiFeCo oxide as an efficient and sustainable catalyst for the oxygen evolution reaction

“…The overpotentials at various current densities are shown in Figure 5C for each catalyst. The lowest overpotential (248 mV at 1 mA cm −2 ) obtained from the ternary NiFeCo oxide electrode is comparable to the values reported for complex binary and ternary compound electrodes such as NiFe-LDH/rGO catalyst (296 mV), 38 NiFe (OH)x/FeS/IF (245 mV), 39 Fe 0.2 Ni 1.8 OOH/EGSI (237 mV), 40 Ni 2 Fe/ rGO is as low as 285 mV, 41 2D NiFe-based metal-organic framework (310 mV), 42 NiCoFe layered triple hydroxides (239 mV), 17 FeCoNi (288 mV), 14 and trimetallic NiFeMo (238 mV). 19 For fair comparison, we provided additional FeCo and NiCo metal oxide data as Supporting Information.…”

Engineering active sites on hierarchical transition bimetal oxides/sulfides heterostructure array enabling robust overall water splitting

“…Apart from morphology engineering, the hybrids can be extensively constructed by use of different transition-metal electrocatalysts through heterostructure engineering, regulating electron transfer and active site as well as the activity owe to the construction of coupling interfaces and the synergistic effect of the heterostructures. For instance, a large number of the heterostructures, such as NiMo/NiMoO x 8 , Co 3 O 4 /Fe 0.33 Co 0.66 P 16 , Ni 2 P/NiP 2 17 , NiFe(OH) x /FeS 18 , Pt 2 W/WO 3 19 , CuCo/CuCoO x 20 , Co(OH) 2 /PANI 21 , FeOOH/Co/FeOOH 22 , Co 0.85 Se/NiFe/graphene 23 , Ni 3 N/VN 24 , NiCu–NiCuN 25 , have been extensively synthesized for the enhanced electrochemical activities. Typically, sulfides-based heterostructures, such as CoS-doped β-Co(OH) 2 /MoS 2+ x 26 , MoS 2 /Fe 5 Ni 4 S 8 27 , MoS 2 /Ni 3 S 2 28 , NiS 2 /MoS 2 29 , MoS 2 /Co 9 S 8 /Ni 3 S 2 /Ni 30 , and MoS 2 /(Co,Fe,Ni) 9 S 8 coupled FeCoNi-based arrays 31 , have been systematically explored for the improved activities of electrochemical water splitting.…”

Ultrathinning Nickel Sulfide with Modulated Electron Density for Efficient Water Splitting

“…[15][16][17][18] At present, noble Pt metal and Ir/Ru-based oxides are the benchmark electrocatalysts to speed up the HER and the OER, respectively. [19][20][21][22][23] Unfortunately, the tremella-like Ni 3 S 2 /MnS-O with abundant oxygen vacancies, which was favorable for HER and OER. [37] An in situ formation of {111} faceted Ni 3 S 2 on the surface of nickel foam toward HER and OER via a one-step hydrothermal process in a Na 2 S aqueous solution was also demonstrated.…”