Fluorine Engineered Self‐Supported Ultrathin 2D Nickel Hydroxide Nanosheets as Highly Robust and Stable Bifunctional Electrocatalysts for Oxygen Evolution and Urea Oxidation Reactions

Abstract

Developing highly efficient noble‐metal‐free electrocatalysts with a scalable and environmentally friendly synthesis approach remains a challenge in the field of electrocatalytic water splitting. To overcome this problem, self‐supported fluorine‐modified 2D ultrathin nickel hydroxide (F‐Ni(OH)2) nanosheets (NSs) for the oxygen evolution reaction (OER) and urea oxidation reaction (UOR) are prepared with a scalable and ascendant one‐step synthesis route. The enhanced redox activity, electrical conductivity and a great number of exposed active sites of the heterogeneous catalysts improve charge migration for the electrocatalytic reactions. The density of states of the d orbitals of the Ni atoms significantly increases near the Fermi level, thereby indicating that the Ni atoms near the F‐dopants promote electrical conduction in the Ni(OH)2 monolayer. The F‐Ni(OH)2 electrocatalyst exhibits notable OER and UOR activity with onset potentials of 1.43 and 1.16 V versus RHE, respectively required to reach 10 mA cm−2, which are comparable to those of commercial noble‐metal‐based electrocatalysts. With RuCo‐OH nanospheres, the settled F‐Ni(OH)2||RuCo‐OH cell requires merely 1.55 and 1.37 V to reach 10 mA cm−2 with superb durability for 24 h in overall water and urea electrolysis, respectively. Overall, high‐quality, and efficient noble‐metal‐free electrocatalysts for overall water and urea electrolysis can be prepared with a simple, scalable, and reproducible preparation method.

In situ electrochemical activation of Co(OH)2@Ni(OH)2 heterostructures for efficient ethanol electrooxidation reforming and innovative zinc–ethanol–air batteries

“…S10 (ESI †), the introduction of fluorine also effectively improves the EOR performance of the catalyst, which can be attributed to the electron modulation by F À ions to facilitate the Ni(OH) 2 /NiOOH transformation. 39,40 In Fig. 2b, the electrochemical activation of F-doped Ni(OH) 2 was much weaker than Co(OH) 2 @Ni(OH) 2 .…”

Ni-based ultrathin nanostructures for overall electrochemical water splitting

“…Patil et al also utilized FESEM to study the morphology of F-Ni(OH) 2 NSs, finding that they form ultrathin, fine vertically oriented 2D NSs with a high density. 18 HRTEM was used to investigate the morphological and structural characteristics of the produced samples in more depth. In the HRTEM image of Ni/NiO/NC in Fig.…”

“…16 Furthermore, in terms of the electronic structure, the density of states of the d orbitals of the Ni atoms has been shown to significantly increase near the Fermi level, which increases the density of accessible active sites. 17,18 To support experimental prediction, many diverse nickel-based structures have been experimentally proven to be at the forefront of transition metal catalysts having the most promising constituents with variable oxidation states ranging from −1 to +4, which make it possible toward undergoing various electronic transitions. 19–24…”

“…16 Furthermore, in terms of the electronic structure, the density of states of the d orbitals of the Ni atoms has been shown to significantly increase near the Fermi level, which increases the density of accessible active sites. 17,18 To support experimental prediction, many diverse nickel-based structures have been experimentally proven to be at the forefront of transition metal catalysts having the most promising constituents with variable oxidation states ranging from À1 to +4, which make it possible toward undergoing various electronic transitions. [19][20][21][22][23][24] Nano-sized materials are well known for possessing interesting physical and chemical properties that arise from unique features such as high specific surface areas, the presence of abundant active sites, an enhanced rate of charge transfer and effective diffusion paths.…”

Circumventing Challenges: Design of Anodic Electrocatalysts for Hybrid Water Electrolysis Systems

“…Favorable adsorption and desorption energies of reactants and products were thus optimized for higher HER and UOR electrocatalytic activities (Figure 14m-o). Additionally, other works of Ru-doping in Ru-Co 2 P/N-C/NF [151] and NiFeRu-LDH, [152] V-doping in Fe, V-NiS/NF, [153] V-FeNi 3 N/Ni 3 N, [154] NiMoV LDH/NF [155] and V-Ni 3 N/NF, [156] Fe-doping in CoNiFeS-OH, [157] P doping in F-P-Co 3 O 4 , [158] F-doping in F-Ni(OH) 2 [159] were also recently reported, inducing electrocatalytic UOR activity enhancement in different catalyst systems.…”