Dual-phase Cu-Co/CoO heterojunctions for efficient tandem nitrate electroreduction via smooth intermediate handover

doi:10.1016/S1872-2067(25)64840-6

Abstract

Abstract:

Tandem electrocatalysis offers considerable potential for selectively converting nitrate ions (NO₃^-) to ammonia (NH₃) via electrochemical reduction, yet its practical application is often hampered by sluggish nitrite ions (NO₂^-) intermediate transfer between spatially separated active sites and mismatched reaction potentials, which together constrain conversion efficiency and limit high Faradaic efficiency (FE) to a narrow operating window. Herein, we report a rationally designed dual-phase Cu-doped Co/CoO (Cu-Co/CoO) heterojunction, featuring spatially distinct yet synergistic active sites and abundant atomic-scale heterointerfaces that enable accelerated tandem catalysis. Mechanistic investigations reveal that the Cu-doped CoO domain predominantly catalyzes the reduction of NO₃^- to NO₂^-, which is rapidly transferred across the heterointerface to the Cu-doped Co domain for further hydrogenation to NH₃. As a result, the Cu-Co/CoO catalyst achieves a high FE exceeding 85% and sustains high NH₃ yields across a broad potential range. Notably, the catalyst achieves a remarkable NH₃ yield of 27.3 mmol h^-1 mg_cat^-1 and an NH₃ partial current density of 0.58 A cm^-2 at -0.8 V (vs. RHE). Integration into a Zn-NO₃^- battery system further enables simultaneous high-rate NH₃ production and power output. This work establishes a viable methodology for engineering high-performance tandem electrocatalysts and offers new insights into interfacial engineering for renewable NH₃ synthesis.

Key words: Interfacial engineering, Dual-phase heterojunction, Nitrate reduction, Tandem electrocatalysis, Wide potential window

Binjie Du, Yuhang Xiao, Xiaohong Tan, Weidong He, Yingying Guo, Hao Cui, Chengxin Wang. Dual-phase Cu-Co/CoO heterojunctions for efficient tandem nitrate electroreduction via smooth intermediate handover[J]. Chinese Journal of Catalysis, 2026, 80: 270-281.

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URL: https://www.cjcatal.com/EN/10.1016/S1872-2067(25)64840-6

https://www.cjcatal.com/EN/Y2026/V80/I1/270

Figures/Tables 5

Fig. 1. (a) Schematic diagram of synthesized biphasic heterostructure Cu-Co/CoO. TEM images (b) and High-magnification images (c-f) of Cu-Co/CoO. The corresponding SAED image of Cu-Co/CoO illustrated in (b). (g) Elemental mapping image (O = red, Cu = green, Co = yellow). (h-j) XRD patterns.

Fig. 2. XPS spectra of Cu 2p (a), Co 2p (b), and O 1s (c) for catalysts. (d) XPS valence band spectra measured for Cu-Co/CoO and Co/CoO. (e) Normalized Co K-edge XANES spectra of Cu-Co/CoO, Co foil and Com-CoO. (f) Corresponding k2-weighted FT-EXAFS spectra.

Fig. 3. (a) LSV curves in 1 mol L-1 KOH with and without 0.1 mol L-1 NO3-. Different potential of NH3 FEs (b) and NH3 production rates and mass activities (c). Comparison of the mass activity (d) and specific activity (e) between Cu-Co/CoO and literature-reported NO3RR catalysts. (f) 1H NMR spectra of Cu-Co/CoO after electrocatalysis using 15NO3- or 14NO3- as the N-source. (g) NH3 yield and FE retention during 12-cycle durability testing (-0.6 V vs. RHE).

Fig. 4. (a) LSV curves of Cu-Co/CoO and Co/CoO recorded in 1 mol L-1 KOH with 0.1 mol L-1 KNO2. (b) Comparisons of FENH3 at -0.6 V (vs. RHE) in 1 mol L-1 KOH + 0.1 mol L-1 KNO3 vs. 1 mol L-1 KOH + 0.1 mol L-1 KNO2. (c,d) The potential resolved in-situ Raman spectra of Cu-Co/CoO and Cu-Co for NO3RR. In-situ ATR-FTIR spectra under 1 mol L-1 KOH with 0.1 mol L-1 KNO3 solution: Cu-Co/CoO (e) vs. Co/CoO (f).

Fig. 5. (a) Schematic diagram of the developed ZNB based on Cu-Co/CoO cathode for both nitrate conversion and electricity supply. (b) The performance of open-circuit voltage. (c) The discharge curve of Cu-Co/CoO ZNB and the resultant power density. (d) Discharge current density-dependent NH3 production rates and FE within the Zn-NO3- electrochemical system. (e) Ladder-shaped discharge measurement derived from the Cu-Co/CoO ZNB system. (f) Comparison of power density and NH3 yield rate between Cu-Co/CoO and recently reported cathodes in Zn-NO3- battery. (g) The long-term discharge-charge test of Zn-NO3- cell.

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