Binder-free nickel borate/nickel hydroxide bifunctional catalyst for coupled nitrate reduction and glycerol oxidation towards sustainable ammonia production Phiralang Marbaniang 1 , Sagar Ingavale 1 , Warunyoo Yoopensuk 1 , Wanwisa Limphirat 2 , Hao Wu 3 , Weerachon Tolek 4 , Wijak Yospanya 5 , Joongjai Panpranot 6 , Qian Wang 7 , Soorathep Khaewhom 8 , Chanon Pornrungroj 9 1 Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand, 2 Synchrotron Light Research Institute, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand, 3 Graduate School of Engineering, Nagoya University, Furo- cho, Chikusa-ku, Nagoya, Japan; Institute for Advanced Research, Nagoya University, Nagoya, Japan, 4 Centre of Excellence on Catalysis and Catalytic Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand, 5 Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba- ku, Sendai, Miyagi 980-8577, Japan, 6 Centre of Excellence on Catalysis and Catalytic Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand, 7 Graduate School of Engineering, Nagoya University, Furo- cho, Chikusa-ku, Nagoya, Japan; Institute for Advanced Research, Nagoya University, Nagoya, Japan, 8 Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand; Bio-Circular-Green-economy Technology & Engineering Center (BCGeTEC), Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand; Center of Excellence on Advanced Materials for Energy Storage, Chulalongkorn University, Bangkok 10330, Thailand, 9 Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand; Bio-Circular-Green-economy Technology & Engineering Center (BCGeTEC), Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand E-mail: chanon.po@chula.ac.th 3 ) represents a promising strategy for sustainable chemical synthesis by utilizing waste-derived nitrogen sources and renewable electricity. 1 As part of the integrated power-to-X scheme, this approach generated ammonia production in ambient condition, lower impact as compared to the conventional Haber-Borch processes. Here, we report a binder-free mixed-phase of Nickel borate/Nickel hydroxide bifunctional electrocatalyst directly grown on Ni foam that enables efficient NO 3 RR without using an external Ni precursor. The optimized catalyst achieves a high NH 3 yield rate of ~53 mg h- 1 cm- 2 The electrochemical reduction of nitrate (NO 3 - ) to ammonia (NH and a Faradaic efficiency of ~81% at −0.55 V vs. RHE. To further reduce the energy input, we couple NO 3 RR with GOR at the anode, replacing the energy-intensive oxygen evolution reaction (OER). The integrated NO 3 RR||GOR system operates at a low cell voltage of 1.47 V (10 mA cm- 2 ), producing 510 μg h- 1 cm- 2 of NH 3 with ~63% Faradaic efficiency and a glycerol conversion rate of ~23%. The hybrid electrolyzer enabling a potential energy- saving of ~13% compared to NO 3 RR||OER. This work advances the development of electrochemical platforms for sustainable ammonia synthesis by highlighting cost-effective, energy-saving and environmental benefits of coupling reaction. References 1. Fan, Y., Yan, Y., Nwokonkwo, O. et al. Tuning nitrate reduction reaction selectivity via selective adsorption in electrified membranes. Nat Chem Eng 2 , 379–390 (2025). https://doi.org/10.1038/s44286-025-00237-3
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