Efficient Photoelectrocatalytic Synthesis of Ammonia by Superionic Conductor with Mixed Ion/Electron Conduction.

Wang, Xiaxin; Li, He; Zou, Yuxiu; Xiao, Hang; Teng, Wenkai; Chong, Ben; Xia, Mengyang; Li, Yang et al. · Adv Mater · 2025

basic_science · Level V

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Abstract

Photoelectrochemical (PEC) nitrate reduction shows substantial potential for solar-to-ammonia (NH<sub>3</sub>) conversion. However, low electron density and disordered electron conduction of conventional catalysts result in limited performance and low Faraday efficiency. Herein, a FePS<sub>2.66</sub>Li<sub>0.87</sub> superionic conductor (SIC) is developed by introducing lithium ions into van der Waals immobile layered of FePS<sub>3</sub> catalyst. This layered crystal framework facilitates high-concentration lithium ions confinement and long-range diffusion at room temperature, transitioning the conduction mechanism from electronic to mixed ionic/electronic. The typical nanofluidic ion transport leads to a high ionic conductivity of 16.4 mS cm<sup>-1</sup> at room temperature and enhanced electronic conductivity of 5 × 10<sup>-6</sup> S cm<sup>-1</sup>. Furthermore, mobile lithium ions within interlayers enhance the interaction between the low-lying 3d<sub>yz</sub> orbitals of Fe interacting with 2a<sub>2</sub> empty antibonding orbitals of NO<sub>3</sub> <sup>-</sup>. An excellent PEC ammonia production of 134.18 µmol cm<sup>-2</sup> h<sup>-1</sup> with 96.95% Faradaic efficiency is achieved, and the corresponding solar-to-NH<sub>3</sub> efficiency of 57.13% offers a promising pathway toward sustainable ammonia production.