Oxygen-bridged Ni-O-Co electronic conduits enable spatially partitioned dual active sites for ampere-scale hydrazine electrolysis

doi:10.1016/S1872-2067(26)65268-0

Abstract

Abstract:

Hydrazine electrolysis offers a sustainable route for energy-efficient hydrogen production, yet the development of electrocatalysts capable of ampere-scale performance remains challenging. Herein, we show a Janus tubular Co₃O₄/NiCu heterostructure supported on nickel foam (Co₃O₄/NiCu/NF) via a voltammetric-assisted alloying-selective dealloying process. The generated oxygen-bridged Ni-O-Co dual active sites at the heterointerface act as a bifunctional catalyst for the hydrazine oxidation reaction (HzOR) and hydrogen evolution reaction (HER) at ultralow overpotentials of 451 mV and 263 mV to attain 3 A cm^-2, respectively. Only 2.249 V cell voltage is required for overall hydrazine splitting (OHzS) to achieve the same industrial-scale current density alongside excellent stability. Synchrotron X-ray absorption spectroscopy and density functional theory calculations reveal that the Ni-O-Co bridges spatially anchor Ni and Co as adjacent dual sites and induce interfacial charge redistribution. Oxygen functions as an electronic conduit to synergistically modulate the catalytic functions: Co sites receive electrons via the unique Ni-O-Co sites to optimize H adsorption for HER, whilst Ni sites with higher oxidized states facilitate N₂H₄ dehydrogenation for HzOR. This work offers a robust strategy for designing dual-site heterostructured electrocatalysts for ampere-level hydrogen production.

Key words: Alloying-dealloying strategy, Janus tubular heterostructure, Electronic conduits, Dual active sites, Hydrazine electrolysis

Qiangqiang Sun, Zhao Li, Meina Jiang, Dan Wang, Baoyue Cao, Ning Nan, Chun Li, Chunsheng Zhou, Chuan Zhao, Yibing Li. Oxygen-bridged Ni-O-Co electronic conduits enable spatially partitioned dual active sites for ampere-scale hydrazine electrolysis[J]. Chinese Journal of Catalysis, 2027, 92: 192-205.

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URL: https://www.cjcatal.com/EN/10.1016/S1872-2067(26)65268-0

https://www.cjcatal.com/EN/Y2027/V92/I1/192

Figures/Tables 6

Fig. 1. (a) Schematic illustration showing the stepwise fabrication of Co3O4/NiCu/NF. (b,c) FESEM images of the tubular structure. (d) TEM image with the inserted SAED pattern. (e,f) HRTEM images for the enlarged view of the green and red regions in (d). (e1,e2) Inverse FFT filtered images obtained from (e). XRD pattern (g), HAADF-STEM image and corresponding mapping images (h) of Co3O4/NiCu/NF.

Fig. 2. (a,b) Ni K-edge XANES spectra and Ni R-space EXAFS spectra. (c,d) Co K-edge XANES spectra and Co R-space EXAFS spectra. (e) WT plots of Co3O4, CoO and Co3O4/NiCu at Co K-edge. (f) WT plots of Ni foil, NiO, NiCu, and Co3O4/NiCu at Ni K-edge.

Fig. 3. HER performance of Co3O4/NiCu/NF. (a) iR-corrected LSV curves. (b) Overpotential comparison with reported HER catalysts at 1000 mA cm-2. (c) Tafel plots. (d) CV curves (5-200 mV s-1, 0 to 0.10 V vs. RHE). (e) Cdl estimation from current density at 0.05 V. (f) Nyquist plots at -50 mV (inset: high-frequency region). (g) Multi-step chronopotentiometry. (h) LSV curves before/after 5000 CV cycles. (i) Long-term stability at -100/-1000 mA cm-2 for 120 h.

Fig. 4. Electrocatalytic HzOR performance of Co3O4/NiCu/NF. (a) iR-corrected LSV curves. (b) Activity comparison between Co3O4/NiCu/NF and reported HzOR catalysts. (c) Tafel plots from (a). (d) In-situ Bode phase plots under different potentials (-25 to 125 mV) for Co3O4/NiCu/NF. (e) Bode phase plots for Co3O4/NiCu/NF, Co3O4/NF, NiCu/NF and NF at 0 mV. (f) Comparison of peak phase degree and peak frequency for Co3O4/NF, NiCu/NF and Co3O4/NiCu/NF. (g) LSV before/after 5000-cycle CV tests. (h) Chronopotentiometry. (i) Double-step chronoamperometry.

Fig. 5. Hydrazine-assisted water electrolysis. Cell voltage comparison (a) and measured vs. calculated H2 production (inset: GC spectra) (b). (c) LSV curves of Co3O4/NiCu/NF in hydrazine electrolysis before/after 5000 CV cycles. (d) Chronopotentiometric test of Co3O4/NiCu/NF electrolyzer at different current densities. (e) Comparison of the Co3O4/NiCu/NF OHzS system with recently reported catalysts. (f) Long-term durability of the Co3O4/NiCu/NF hydrazine electrolyzer at 0.5 and 1.0 A cm-2 during successive 120 h tests without iR correction.

Fig. 6. (a) Charge density difference of Co3O4/NiCu. (b) Density of states plots of the d-band in NiCu, Co3O4 and Co3O4/NiCu as well as the d-band center. Free energies for H adsorption on the Ni site of Ni, NiCu and Co3O4/NiCu, Co site-Co3O4/NiCu (c) and the corresponding atomic structure model (d). (e) Free energy diagram of HzOR and the adsorption models of the intermediates on NiCu and Co3O4/NiCu surfaces, respectively. (f) In-situ Raman spectra of Co3O4/NiCu/NF in 1 mol L‒1 KOH + 0.5 mol L‒1 N2H4 from OCP to 0.25 V (vs. RHE). (g,h) Potential-dependent in situ FTIR spectra from OCP to 1.3 V (vs. RHE).

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