α‐Ni(OH)₂ Originated from Electro‐Oxidation of NiSe₂ Supported by Carbon Nanoarray on Carbon Cloth for Efficient Water Oxidation

Abstract

wide applications are highly restricted by their low abundance and high cost. [7][8][9] In recent years, tremendous research efforts have been devoted to developing earthabundant, low-cost, and highly-efficient OER electrocatalysts, among which transition metal based compounds including transition metal oxides, [10][11][12] hydroxides, [13][14][15][16][17][18] phosphides, [19,20] sulfides, [21,22] and selenides [23][24][25] have been demonstrated to have favorable electrocatalytic property and durability. Meanwhile, to further enhance the activity of these electrocatalysts, two common approaches including morphology control and composition modification have been adopted to either increase the number of active sites or optimize their intrinsic activities. [26][27][28] Through these efforts, a large number of transition metal-based OER electrocatalysts with improved activity have been explored. However, to the best of our knowledge, most of the reported nonprecious electrocatalysts still need overpotentials larger than 200 mV to reach 10 mA cm −2 , [29][30][31] leaving substantial room for improvement.In addition, it is noteworthy that the actual "active phase" of transition metal oxides/hydroxides for OER is oxyhydroxide, and this has been verified by many researchers. For example, Boettcher and coworkers reported a series of metal oxides thin films for OER, and revealed the in situ formation of layered hydroxides/oxyhydroxides were the active catalysts. [32] Bell and coworkers discovered that Ni-Fe layered double (oxy)hydroxide was the critical phase for OER when introducing Fe impurities into Ni(OH) 2 . [33,34] Unlike the comprehensive investigation over transition metal oxides/hydroxides, the studies on transition metal chalcogenides (sulphides/selenides) for OER have not been thoroughly investigated. The conclusions on these OER electrocatalysts are even contradictory. For example, Xu et al. reported that FeNi diselenides would transform entirely into metal oxides and serve as active phase for OER purely measuring post-OER samples. [24] Some works reported the good stability of transition metal selenide under OER. [35,36] There is hardly any uniform conclusion regarding these transition metal chalcogenide electrocatalysts.In this work, supersmall α-Ni(OH) 2 was synthesized via the electro-oxidation of NiSe 2 and served as efficient OER electrocatalyst. Specifically, NiSe 2 was fabricated onto carbon nanoarray on carbon cloth (NiSe 2 @CNA@CC) through Development of effective oxygen evolution reaction (OER) electrocatalysts has been intensively studied to improve water splitting efficiency and cost effectiveness in the last ten years. However, it is a big challenge to obtain highly efficient and durable OER electrocatalysts with overpotentials below 200 mV at 10 mA cm −2 despite the efforts made to date. In this work, the successful synthesis of supersmall α-Ni(OH) 2 is reported through electrooxidation of NiSe 2 loaded onto carbon nanoarrays. The obtained α-Ni(OH) 2 shows excellent activity and long-term stabil...

Optimization of oxygen evolution activity by tuning e*g band broadening in nickel oxyhydroxide

“…The structural reconstruction of the pre-catalyst is a slow process that has been verified using operando XAFS in our previous studies that involved NiS 2 and NiSe 2 . 11,15 According to the chronopotentiometry results, the measured potential increased gradually during the initial stage (0 to 1–2 hours), which could be ascribed to the phase transition from NiS 2 /NiSe 2 /Ni 5 P 4 to Ni(OH) 2 (Fig. S7, ESI†).…”

“…The full transformations of anion-regulated pre-catalysts into NiOOH were proven in our previous work. 11,15 Yan et al also reported that Co 9 S 8 would be fully reconstructed into CoOOH during the OER process. 22 Here, it should be noted that our findings were different from the previous partially reconstructed NiOOH systems, such as the formation of the coreshell structure, 12,13 the residual anion atoms residing on the surface lattice oxygen sites, 14 etc.…”

Atomic Heterointerface Engineering of Ni2P‐NiSe2 Nanosheets Coupled ZnP‐Based Arrays for High‐Efficiency Solar‐Assisted Water Splitting

“…In addition to specific peaks of the ZnP NRs, some peaks locate at 40.7°, 47.3°, 54.2°, and 66.5° are attributed to the (111), (210), (300), and (310) crystal planes of Ni 2 P phase (JCPDS #65-9706). [31] Meanwhile, other peaks appear at 30.0°, 33.7°, 36.9°, 42.9°, 45.3°, 50.7°, 55.6°, 57.9°, and 62.2° are associated with the (200), (210), (211), (220), ( 221), (311), (230), (321), and (400) crystal planes of NiSe 2 phase (JCPDS#11-0552), [32] validating the formation of Ni 2 P-NiSe 2 shell, fully consistent with the TEM observations. Crystalline features of the ZnP@Ni 2 P and ZnP@NiSe 2 materials are confirmed by their XRD patterns in Figure S6a,b, Supporting Information, respectively.…”

NiSe2 Nanoparticles Decorated on Carbon Nanosheet Arrays as Anodes for Sodium Storage

“…Figures A and S6 display the representative TEM images of an individual NiSe 2 /C hybrid nanosheet from which one can see that the thin and continuous carbon nanosheets are decorated with numerous NiSe 2 nanoparticles (average size of 45 nm) and part of the neighboring NiSe 2 nanoparticles have emerged into big ones. Moreover, the abundant mesopores possessing a size of about 25 nm measured by BET (Figure S7) as distributed in the carbon nanosheet are able to facilitate the infiltration of electrolytes, shorten the ion diffusion distance, and improve the rate performance of the active materials. − The corresponding selected area electron diffraction (SAED) pattern (Figure A inset) indicates that the observed spots are assigned to the crystal planes of (200), (210), and (220) of cubic phase NiSe 2 . , The HRTEM measurement (Figures C and S8) clearly shows the distinct interfaces between the formed NiSe 2 nanoparticles and amorphous carbon nanosheets inherited from the introduced glucose during the carbonization process. It is revealed that the NiSe 2 nanoparticles are closely integrated on the supporting carbon nanosheet with intimate contact, which can ensure the much enhanced structural integrity and elevated electrical conductivity of the NiSe 2 nanoparticles.…”