Surface engineering of hierarchical Ni(OH)2 nanosheet@nanowire configuration toward superior urea electrolysis

Yue, Zhihao; Yao, Siyu; Li, Yuanzhen; Zhu, Wenxin; Zhang, Wentao; Wang, Rong; Wang, Jing; Huang, Lunjie; Zhao, Dongyang; Wang, Jianlong

doi:10.1016/j.electacta.2018.02.059

Cited by 68 publications

(37 citation statements)

References 51 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

153

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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

153

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“…Recent research on UOR catalysts has made a series of progress, among which transition metal oxides (TMO) such as two‐dimensional (2D) MnO 2 crystals, [ 16 ] Ni(OH) 2 nanosheets, [ 15,24 ] NiMo‐based nanostructures, [ 25,26 ] and other nickel composites [ 27–29 ] have been well developed with commendable performance. However, the UOR activity of these catalysts needs to be further improved and higher stability is still highly required.…”

Section: Introductionmentioning

confidence: 99%

Bimetal Schottky Heterojunction Boosting Energy‐Saving Hydrogen Production from Alkaline Water via Urea Electrocatalysis

Wang

Mao

et al. 2020

Adv Funct Materials

248

163

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Hydrogen production via water electrocatalysis is limited by the sluggish anodic oxygen evolution reaction (OER) that requires a high overpotential. In response, a urea-assisted energy-saving alkaline hydrogen-production system has been investigated by replacing OER with a more oxidizable urea oxidation reaction (UOR). A bimetal heterostructure CoMn/CoMn 2 O 4 as a bifunctional catalyst is constructed in an alkaline system for both urea oxidation and hydrogen evolution reaction (HER). Based on the Schottky heterojunction structure, CoMn/CoMn 2 O 4 induces self-driven charge transfer at the interface, which facilitates the absorption of reactant molecules and the fracture of chemical bonds, therefore triggering the decomposition of water and urea. As a result, the heterostructured electrode exhibits ultralow potentials of −0.069 and 1.32 V (vs reversible hydrogen electrode) to reach 10 mA cm −2 for HER and UOR, respectively, in alkaline solution, and the full urea electrolysis driven by CoMn/CoMn 2 O 4 delivers 10 mA cm −2 at a relatively low potential of 1.51 V and performs stably for more than 15 h. This represents a novel strategy of Mott-Schottky hybrids in electrocatalysts and should inspire the development of sustainable energy conversion by combining hydrogen production and sewage treatment.

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“…However, Ni(OH) 2 can further react with OH − from the electrolyte to regenerate NiOOH active sites. Apart from the formation of Ni(OH) 2 in alkaline media, the direct utilization and mechanistic studies on modified Ni(OH) 2 are also reported for urea electrolysis in earlier published works …”

Section: Urea Electrolysis For Hydrogen Productionmentioning

confidence: 99%

Designing Advanced Catalysts for Energy Conversion Based on Urea Oxidation Reaction

Zhu

Liang

Zou

2020

Small

372

270

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Urea oxidation reaction (UOR) is the underlying reaction that determines the performance of modern urea‐based energy conversion technologies. These technologies include electrocatalytic and photoelectrochemical urea splitting for hydrogen production and direct urea fuel cells as power engines. They have demonstrated great potentials as alternatives to current water splitting and hydrogen fuel cell systems with more favorable operating conditions and cost effectiveness. At the moment, UOR performance is mainly limited by the 6‐electron transfer process. In this case, various material design and synthesis strategies have recently been reported to produce highly efficient UOR catalysts. The performance of these advanced catalysts is optimized by the modification of their structural and chemical properties, including porosity development, heterostructure construction, defect engineering, surface functionalization, and electronic structure modulation. Considering the rich progress in this field, the recent advances in the design and synthesis of UOR catalysts for urea electrolysis, photoelectrochemical urea splitting, and direct urea fuel cells are reviewed here. Particular attention is paid to those design concepts, which specifically target the characteristics of urea molecules. Moreover, challenges and prospects for the future development of urea‐based energy conversion technologies and corresponding catalysts are also discussed.

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Surface engineering of hierarchical Ni(OH)2 nanosheet@nanowire configuration toward superior urea electrolysis

Cited by 68 publications

References 51 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

Bimetal Schottky Heterojunction Boosting Energy‐Saving Hydrogen Production from Alkaline Water via Urea Electrocatalysis

Designing Advanced Catalysts for Energy Conversion Based on Urea Oxidation Reaction

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Surface engineering of hierarchical Ni(OH)2 nanosheet@nanowire configuration toward superior urea electrolysis

Cited by 68 publications

References 51 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

Bimetal Schottky Heterojunction Boosting Energy‐Saving Hydrogen Production from Alkaline Water via Urea Electrocatalysis

Designing Advanced Catalysts for Energy Conversion Based on Urea Oxidation Reaction

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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