Exploiting underpotential deposited hydrogen enables energy-efficient nitrate electroreduction to ammonia.
basic_science · Level V
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- Record sourced from PubMed, PMID 41917047.
- Also identified by DOI 10.1038/s41467-026-71299-x.
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Abstract
Electrochemical nitrate reduction in alkaline media offers a sustainable route for ammonia synthesis at rates rivaling those of the Haber-Bosch process. However, its energy efficiency is limited by sluggish nitrate deoxidation and hydrogenation, compounded by challenges in proton supply via H<sub>2</sub>O dissociation. Here, we develop an enzyme-like substrate transport channel through a hierarchical arrangement of metallic Ag and Ru nanophases, to enable cascade nitrate-to-ammonia conversion and optimize underpotential-deposited hydrogen utilization. Operando characterization and theoretical calculations reveal that Ag-Ru electronic synergy regulates underpotential-deposited hydrogen coverage at Ru-centered active sites by coupling facilitated H<sub>2</sub>O dissociation with *OH-mediated site regeneration, thereby promoting nitrite relay conversion. Our underpotential-deposited hydrogen-assisted nitrate electroreduction system delivers a half-cell ammonia energy efficiency of 53.7% at 0.2 V versus RHE with near-unity Faradaic efficiency across a wide nitrate concentration range, and an ammonia partial current density of 2.2 A cm<sup>-2</sup> at 0 V versus RHE. Pairing cathodic nitrate reduction with anodic H<sub>2</sub> oxidation enables ammonia production costs below $1.15 kg<sup>-1</sup> while maintaining sustained energy efficiency over 100 h at 200 mA cm<sup>-2</sup>.