In Situ Reconstructed Zn doped Fe_xNi_(1−x)OOH Catalyst for Efficient and Ultrastable Oxygen Evolution Reaction at High Current Densities

Abstract

the global energy and environmental issues. [1][2][3] Its half-reaction, oxygen evolution reaction (OER), is considered as the key bottleneck in water splitting owing to its multiple protons and electron transfer. [4,5] Through precious metal oxides such as IrO 2 and RuO 2 exhibit effective OER activity, the scarcity, high cost, and inferior stability hinder their widespread applications. [6] The development of highly active electrocatalysts based on earthabundant elements is a highly promising solution to above predicament. However, at present, few noble-metal-free electrocatalysts can meet the requirements of commercial alkaline water electrolysis: afford the current density of 1000 mA cm −2 with stable operation over 100 h. [7,8] Therefore, developing noble-metal-free electrocatalysts with high efficiency and outstanding durability at the large current densities is imperative yet challenging.Iron (Fe)-based materials, especially FeOOH, have recently drawn great attention as promising OER catalysts due to their abundance, cost-effectiveness, and environmental friendliness. [9][10][11] It is reported that the intrinsic activity of FeOOH for OER is higher than that of NiOOH and CoOOH. [12] Nevertheless, the OER performance of FeOOH is far from satisfactory DevelopingFeOOH as a robust electrocatalyst for high output oxygen evolution reaction (OER) remains challenging due to its low conductivity and dissolvability in alkaline conditions. Herein, it is demonstrated that the robust and high output Zn doped NiOOH-FeOOH (Zn-Fe x Ni (1−x) )OOH catalyst can be derived by electro-oxidation-induced reconstruction from the pre-electrocatalyst of Zn modified Ni metal/FeOOH film supported by nickel foam (NF). In situ Raman and ex situ characterizations elucidate that the pre-electrocatalyst undergoes dynamic reconstruction occurring on both the catalyst surface and underneath metal support during the OER process. That involves the Fe dissolution-redeposition and the merge of Zn doped FeOOH with in situ generated NiOOH from NF support and NiZn alloy nanoparticles. Benefiting from the Zn doping and the covalence interaction of FeOOH-NiOOH, the reconstructed electrode shows superior corrosion resistance, and enhanced catalytic activity as well as bonding force at the catalyst-support interface. Together with the feature of superaerophobic surface, the reconstructed electrode only requires an overpotential of 330 mV at a high-current-density of 1000 mA cm −2 and maintains 97% of its initial activity after 1000 h. This work provides an indepth understanding of electrocatalyst reconstruction during the OER process, which facilitates the design of high-performance OER catalysts.

Electrocatalytic Overall Water Splitting Induced by Surface Reconstruction of an Iron-Modified Ni2P/Ni5P4 Heterojunction Array Encapsulated into a N-Doped Carbon Layer

“…Furthermore, in situ Raman spectra were collected from 0 to 1.93 V vs RHE to probe the reconstruction phenomena of the Fe-Ni 2 P/Ni 5 P 4 @N-C during the OER process and determine the real active species. As illustrated in Figure a, no obvious peaks appear when the potential is below 1.23 V, whereas two peaks assigned to the Ni–O vibrations from NiOOH at 475 and 550 cm –1 appear and enhance as the potential increases. , When the voltage reaches 1.43 V and above, a new signal at 624 cm –1 appears, corresponding to the characteristic peak of FeOOH . In addition, the broadband in frequencies from 1000 to 1100 cm –1 related to the active oxygen (O–O – ) is also observed, further manifesting that the metal oxyhydroxide formed. , The structure and surface state of post-OER Fe-Ni 2 P/Ni 5 P 4 @N-C were investigated by XRD and XPS analyses.…”

“…As illustrated in Figure 5a, no obvious peaks appear when the potential is below 1.23 V, whereas two peaks assigned to the Ni−O vibrations from NiOOH at 475 and 550 cm −1 appear and enhance as the potential increases. 33,34 When the voltage reaches 1.43 V and above, a new signal at 624 cm −1 appears, corresponding to the characteristic peak of FeOOH. 35 In addition, the broadband in frequencies from 1000 to 1100 cm −1 related to the active oxygen (O−O − ) is also observed, further manifesting that the metal oxyhydroxide formed.…”

Hybrid Heterostructure Ni3N|NiFeP/FF Self‐Supporting Electrode for High‐Current‐Density Alkaline Water Electrolysis

“…The K 2 FeO 4 content probably originated form partially dissolved Fe‐based materials in 30 wt% KOH during the OER. [ 20 ] Besides, the diffraction peaks from Ni(OH) 2 (PDF‐14‐0117) at 38.5 o and 39.1 o are observed, which indicate that the surface of Ni 3 N|NiFeP/FF is gradually oxidized during the OER process to form Ni(OH) 2 , which are real active sites for OER. [ 21 ] The diffraction peaks of metallic nitrides and bimetallic phosphides decrease sharply, which is due to instability of metallic nitrides/phosphides‐based species under OER potential conditions in a high concentration alkaline solution.…”

In Situ Reconstruction NiO Octahedral Active Sites for Promoting Electrocatalytic Oxygen Evolution of Nickel Phosphate

“…The catalytic performance of Ni(OH) 2 –Ni 2 P 4 O 12 /Ti (314.5 mV @ 100 mA cm −2 , Figure 3a) is close to the previously reported Fe(PO 3 ) 2 /Ni 2 P (265.0 mV @ 100 mA cm −2 ), [ 23 ] NiMoN@NiFeN (277.0 mV @ 100 mA cm −2 ), [ 24 ] Zn‐Fe x Ni( 1− x ) OOH (269.0 mV @ 100 mA cm −2 ). [ 25 ] Tafel slope is further applied to evaluate the electrocatalytic kinetics. As illustrated in Figure 3b, the Tafel slopes of Ni(OH) 2 –Ni 2 P 4 O 12 /Ti is only 45.0 mV dec −1 , which is close to RuO 2 /C (39.4 mV dec −1 ) and obviously much smaller than those of the Ni 2 P 4 O 12 /Ti (154.0 mV dec −1 ), suggesting an enhanced OER kinetics.…”