🧾 Title:

Binder-Free Nickel Borate/Nickel Hydroxide Bifunctional Catalyst for Coupled Nitrate Reduction and Glycerol Oxidation Toward Sustainable Ammonia Production

Authors: Phiralang Marbaniang, Sagar Ingavale, Warunyoo Yoopensuk, Wanwisa Limphirat, Hao Wu, Weerachon Tolek, Wijak Yospanya, Joongjai Panpranot, Qian Wang, Soorathep Kheawhom, Chanon Pornrungroj*
Affiliations: Chulalongkorn University, Thailand; University of Science and Technology of China; National Taiwan University; University of Cambridge
Journal: ACS Applied Materials & Interfaces (2025), Vol. 17, pp. 52010–52023
DOI: 10.1021/acsami.5c09453

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🧠 TL;DR (English)

This study presents a binder-free nickel borate/nickel hydroxide (Ni₃(BO₃)₂/Ni(OH)₂) catalyst grown directly on Ni foam for efficient electrochemical nitrate reduction reaction (NO₃RR). By coupling NO₃RR with glycerol oxidation reaction (GOR) at the anode, the system reduces energy input while producing both ammonia (NH₃) and formate. The optimized Ni8:8@Ni electrode achieved an NH₃ yield rate of 1.49 ± 0.04 mmol h⁻¹ cm⁻² and 81 ± 4.8% Faradaic efficiency at −0.55 V vs RHE. The integrated NO₃RR||GOR cell operates at 1.47 V (10 mA cm⁻²) with ~13% energy savings compared to NO₃RR||OER. This bifunctional catalyst platform offers a scalable, energy-efficient route to green ammonia production and value-added co-products.

 

🪴 Plain Language Summary (TH)

งานวิจัยนี้พัฒนาตัวเร่งปฏิกิริยานิกเกิลบอเรต–นิกเกิลไฮดรอกไซด์แบบไม่ใช้สารยึดติด โดยปลูกบนโฟมนิกเกิลโดยตรง เพื่อเปลี่ยนน้ำเสียที่มีไนเตรตให้เป็นแอมโมเนียด้วยกระบวนการทางไฟฟ้าเคมี พร้อมกับออกซิเดชันของกลีเซอรอลซึ่งเป็นผลพลอยได้จากไบโอดีเซล เพื่อประหยัดพลังงานและสร้างผลิตภัณฑ์เคมีมูลค่าสูง ระบบนี้ช่วยลดพลังงานที่ใช้ในการผลิตแอมโมเนียได้ราว 13% และเป็นแนวทางที่มีศักยภาพสำหรับการผลิตแอมโมเนียสีเขียวอย่างยั่งยืน

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🧭 Key Contributions

• First demonstration of binder-free Ni₃(BO₃)₂/Ni(OH)₂ catalyst grown directly on Ni foam using a simple hydrothermal method.

• Achieves high NH₃ yield and Faradaic efficiency for NO₃RR.

• Integrates nitrate reduction with glycerol oxidation, lowering cell voltage.

• Demonstrates 13% energy savings vs conventional NO₃RR||OER systems.

• Provides a dual-function platform for green fertilizer and chemical production.

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• 🧪 Methods

• In situ etching–growth of mixed-phase Ni₃(BO₃)₂/Ni(OH)₂ on Ni foam (urea + boric acid precursors).

• Electrochemical testing in 1 M KOH with 0.1 M KNO₃ at the cathode and 0.1 M glycerol at the anode.

• XRD, SEM/TEM, XAS, XPS used to characterize catalyst structure.

• LSV and CPE used to evaluate catalytic activity and stability.

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• 📊 Key Results

• NH₃ yield: 1.49 ± 0.04 mmol h⁻¹ cm⁻² at −0.55 V vs RHE.

• FENH₃: 81 ± 4.8% (maximum 87%).

• Coupled NO₃RR||GOR voltage: 1.47 V (10 mA cm⁻²).

• Formate yield: 0.101 mmol h⁻¹ cm⁻², FEHCOO⁻ 73%.

• Energy saving: ~13% vs NO₃RR||OER.

• Glycerol conversion: 22.8%.

• Excellent stability over 18 cycles.

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• ⚡ Implications

• Enables decentralized, low-carbon NH₃ production.

• Provides valorization pathway for biodiesel glycerol waste.

• Reduces energy cost of fertilizer production.

• Demonstrates scalable co-electrolysis strategy for circular nitrogen and carbon utilization.

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• 💬 FAQ (Q&A)

• Q1: Why use nitrate instead of N₂ for ammonia synthesis?
  A: Nitrate has higher solubility and lower activation energy than N₂, enabling higher NH₃ yield and lower energy cost.

• Q2: What makes this catalyst binder-free?
  A: The active Ni₃(BO₃)₂/Ni(OH)₂ layer is grown directly from the Ni foam substrate, avoiding polymeric binders that impede charge transfer.

• Q3: What’s the advantage of coupling NO₃RR with GOR?
  A: Replacing OER with GOR lowers cell voltage and enables co-production of formate from glycerol waste.

• Q4: Is this scalable?
  A: A flow cell test at 4 cm² showed comparable performance, indicating good scalability potential.

• Q5: What’s the environmental impact?
  A: This approach addresses nitrate pollution and reduces greenhouse gas emissions associated with conventional Haber–Bosch NH₃ production.

• Q6: Can this be integrated with renewable energy?
  A: Yes. The low operating voltage makes it compatible with intermittent renewable power sources.

• Q7: What is the energy saving compared to conventional systems?
  A: Approximately 13% lower energy demand versus NO₃RR||OER systems.

• Q8: What are the main products of the anodic reaction?
  A: Formate (HCOO⁻) is selectively produced from glycerol.

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• “nitrate reduction catalyst for green ammonia”

• “binder-free nickel borate hydroxide electrolysis”

• “coupled NO3RR GOR low voltage”

• “ammonia synthesis with formate co-production”

• “Ni3(BO3)2 Ni(OH)2 electrocatalyst efficiency”

• “glycerol oxidation energy saving electrolyzer”

• “Chulalongkorn University ammonia research”

• “sustainable fertilizer production 2025”

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• Phiralang Marbaniang, Sagar Ingavale, Warunyoo Yoopensuk, Wanwisa Limphirat, Hao Wu, Weerachon Tolek, Wijak Yospanya, Joongjai Panpranot, Qian Wang, Soorathep Kheawhom, Chanon Pornrungroj. Binder-Free Nickel Borate/Nickel Hydroxide Bifunctional Catalyst for Coupled Nitrate Reduction and Glycerol Oxidation Toward Sustainable Ammonia Production. ACS Applied Materials & Interfaces (2025) 17, 52010–52023. DOI: 10.1021/acsami.5c09453