Iron‐Incorporated α‐Ni(OH)<sub>2</sub> Hierarchical Nanosheet Arrays for Electrocatalytic Urea Oxidation

Xie, Junfeng; Liu, Weiwei; Lei, Fengcai; Zhang, Xiaodong; Qu, Haichao; Gao, Li; Hao, Pin; Tang, Bo; Xie, Yi

doi:10.1002/chem.201803718

Cited by 129 publications

(82 citation statements)

References 35 publications

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“…The contrastive performance of Ni(OH) 2 –NiMoO x /NF for OER and UOR are exhibited in Figure e. The oxidation peaks in the curve of OER belongs to the oxidation of Ni (0), while the phenomenon that no oxidation peak emerges in the polarization curve of UOR is consistent with literature reports . To attain the current density of 50 mA cm −2 , a greatly lowered potential of 143 mV is manifested for UOR compared with pure OER.…”

Section: Methodssupporting

confidence: 86%

Crystalline Ni(OH)₂/Amorphous NiMoO_x Mixed‐Catalyst with Pt‐Like Performance for Hydrogen Production

Dong

Lin

Yao

et al. 2019

Advanced Energy Materials

161

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electrocatalysts, NiMo-based carbides, [10,11] nitrides, [12,13] sulfides, [14] phosphides [15] as well as NiMo-alloy electrocatalysts [16][17][18][19][20][21] can possess remarkable HER capabilities. As the variety of NiMo-based catalysts being enriched, pure NiMo-based oxide or hydroxides have rarely been explored as HER catalysts, instead they usually are coupled with other active components for realizing efficient HER. [22,23] Meantime, it has been proved the effect of accelerating water dissociation of Ni(OH) 2 in alkali [24,25] and the superior catalytic performance of MoO 2 . [26] Herein, we speculate that the alkaline HER performance of NiMo-based (hydr) oxide is greatly underestimated.Inspired by above considerations, a novel 3D porous integrated electrocatalyst Ni(OH) 2 -NiMoO x /NF constituted of crystalline Ni(OH) 2 and amorphous NiMoO x was fabricated through ZnO templateassisted electrodeposition and subsequent KOH soaking operations. Interestingly to note, soaking alters the crystallinity of the amorphous precursor and triggers phase transformation, generating the crystalline/amorphous electrocatalyst. To deliver current densities of 10 and 200 mA cm −2 for alkaline HER, this catalyst requires overpotentials of 36 and 176 mV, respectively. It also displays a much decreased Tafel slope (38 mV dec −1 ) compared with the precursor (92 mV dec −1 ), illustrating an optimized reaction kinetics from Volmer-Heyrovsky step to Heyrovsky step. And the overpotential is only 13 mV increased after the multicurrent step stability test, manifesting its excellent durability. When composed into the two-electrode electrolyzer for ureaassisted electrolysis, a cell voltage of 1.42 V is barely demanded to achieve 10 mA cm −2 . Meanwhile, the catalytic activity can sustain for more than 40 h without declination, proving the feasibility of realizing high-efficient HER through urea-assisted electrolysis. Furthermore, the synergy effect between crystalline Ni(OH) 2 and amorphous NiMoO x are identified through contrastive experiments and the Fourier transform infrared spectroscopy (FTIR) results: Ni(OH) 2 serves for accelerating the dissociation of water (Volmer step) in alkali to generate H*, while amorphous areas are the active sites for H* adsorption and desorption through subsequent Heyrovsky and Tafel steps. This work not only fabricates the electrocatalyst of NiMo-based (hydr) oxides with brilliant HER and urea oxidation reaction (UOR) capabilities, but also discovers a new pathway for designing mixed-crystal materials for other catalysis systems.The Ni(OH) 2 -NiMoO x /NF electrocatalyst was prepared via electrodeposition and soaking operations exhibited in The achievement of effective alkaline hydrogen production from water electrolysis is an active field of research. Herein, an integrated electrode composed of crystalline Ni(OH) 2 and amorphous NiMoO x is fabricated onto nickel foam (denoted as Ni(OH) 2 -NiMoO x /NF). The hydrogen evolution reaction (HER) kinetics are optimized along with phase transformation process...

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Section: Methodssupporting

confidence: 86%

Crystalline Ni(OH)₂/Amorphous NiMoO_x Mixed‐Catalyst with Pt‐Like Performance for Hydrogen Production

Dong

Lin

Yao

et al. 2019

Advanced Energy Materials

161

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“…However, urea electrolysis suffers from intrinsically sluggish kinetics owing to its 6 e − transfer process, complicated intermediates transfer, and multiple gas‐desorption steps . Previous studies showed that nickel oxides exhibited higher catalytic activity for UOR than other metals and metal oxides in alkaline media, where Ni 3+ sites were identified as the catalytic active sites . The typical reaction pathway was proposed as: *CO(NH 2 ) 2 → *CO(NH.NH 2 )→ *CO(NH.NH)→ *CO(NH.N)→ *CO(N 2 )→ *CO(OH)→ *CO(OH.OH)→ *COO, with the desorption of *COO intermediate as the rate‐determining step (RDS) .…”

Section: Figurementioning

confidence: 99%

A Lattice‐Oxygen‐Involved Reaction Pathway to Boost Urea Oxidation

et al. 2019

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The electrocatalytic urea oxidation reaction (UOR) provides more economic electrons than water oxidation for various renewable energy‐related systems owing to its lower thermodynamic barriers. However, it is limited by sluggish reaction kinetics, especially by CO2 desorption steps, masking its energetic advantage compared with water oxidation. Now, a lattice‐oxygen‐involved UOR mechanism on Ni4+ active sites is reported that has significantly faster reaction kinetics than the conventional UOR mechanisms. Combined DFT, 18O isotope‐labeling mass spectrometry, and in situ IR spectroscopy show that lattice oxygen is directly involved in transforming *CO to CO2 and accelerating the UOR rate. The resultant Ni4+ catalyst on a glassy carbon electrode exhibits a high current density (264 mA cm−2 at 1.6 V versus RHE), outperforming the state‐of‐the‐art catalysts, and the turnover frequency of Ni4+ active sites towards UOR is 5 times higher than that of Ni3+ active sites.

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“…Detailed structural analyses indicate that the wire‐on‐sheet nanostructure is single‐crystalline with abundant surface nanowires on the ultrathin 2D layer. Besides, by modifying the metal precursors, controllable elemental doping can be readily achieved, and the as‐obtained Cu, Fe and Ce doped catalysts exhibit remarkable performance on electro‐oxidation reactions such as OER and the urea oxidation reaction . Similarly, 2D nanosheets grown on 1D nanoarrays were also reported, for which the 1D charge transport pathway and the highly exposed surface sites could effectively boost the OER process .…”

Section: Novel Strategies For Optimizing the 2d Oer Catalystsmentioning

confidence: 99%

Preferential Microstructure Design of Two‐Dimensional Electrocatalysts for Boosted Oxygen Evolution Reaction

2019

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evolution reaction (OER) has received substantial concerns owing to its crucial role in improving the overall efficiency of water electrolysis to generate clean hydrogen energy. Focused on the optimization of the earth-abundant OER catalysts, plenty of strategies have been developed aimed on enriching the exposed active sites and enhancing the overall charge transport behavior, thus improving the OER performance. In this Concept paper, the structural merits and limits of the two-dimensional (2D) OER catalysts are discussed in detail. Based on the understandings of the structural influences on the OER catalysis, recent progresses on preferential microstructure design of the 2D OER catalysts are summarized, including designing highly porous single-crystalline catalysts, amorphous/ partially amorphous catalysts, defective catalysts and hierarchical catalysts. This work may provide a useful guidance for future designing of the advanced catalysts for OER.

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Iron‐Incorporated α‐Ni(OH)₂ Hierarchical Nanosheet Arrays for Electrocatalytic Urea Oxidation

Cited by 129 publications

References 35 publications

Crystalline Ni(OH)₂/Amorphous NiMoO_x Mixed‐Catalyst with Pt‐Like Performance for Hydrogen Production

Crystalline Ni(OH)₂/Amorphous NiMoO_x Mixed‐Catalyst with Pt‐Like Performance for Hydrogen Production

A Lattice‐Oxygen‐Involved Reaction Pathway to Boost Urea Oxidation

Preferential Microstructure Design of Two‐Dimensional Electrocatalysts for Boosted Oxygen Evolution Reaction

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Iron‐Incorporated α‐Ni(OH)2 Hierarchical Nanosheet Arrays for Electrocatalytic Urea Oxidation

Cited by 129 publications

References 35 publications

Crystalline Ni(OH)2/Amorphous NiMoOx Mixed‐Catalyst with Pt‐Like Performance for Hydrogen Production

Crystalline Ni(OH)2/Amorphous NiMoOx Mixed‐Catalyst with Pt‐Like Performance for Hydrogen Production

A Lattice‐Oxygen‐Involved Reaction Pathway to Boost Urea Oxidation

Preferential Microstructure Design of Two‐Dimensional Electrocatalysts for Boosted Oxygen Evolution Reaction

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Iron‐Incorporated α‐Ni(OH)₂ Hierarchical Nanosheet Arrays for Electrocatalytic Urea Oxidation

Crystalline Ni(OH)₂/Amorphous NiMoO_x Mixed‐Catalyst with Pt‐Like Performance for Hydrogen Production

Crystalline Ni(OH)₂/Amorphous NiMoO_x Mixed‐Catalyst with Pt‐Like Performance for Hydrogen Production