Limiting Slow Electron Transport in Carbon-Supported Mo-Doped SnO₂ Nanoparticles for Electrocatalytic Ammonia Synthesis

Electrocatalytic nitrogen reduction reaction (NRR) is widely considered a promising and environmentally sustainable ammonia synthesis strategy under ambient conditions, yet the competitive hydrogen evolution reaction (HER) impedes the N 2 to NH 3 conversion efficiency. In this work, carbon-supported Mo-doped SnO 2 nanoparticles (Mo-SnO 2 /C) with a unique tubular structure were designed to suppress free water adsorption, thereby reducing the competing HER and improving the NRR performance. The optimized Mo-SnO 2 /C-3 exhibits a high NH 3 yield of 24.03 μg·h –1 ·mg cat –1 and Faradaic efficiency of 7.11% at −0.8 V vs RHE in 0.1 M Na 2 SO 4 . The transient photovoltage further reveals that limiting the rapid transfer of slow electrons effectively suppresses the kinetically preferred HER process. In addition, in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy further elucidated that the formation of a tubular carbon layer structure improves the hydrophobicity of the catalyst, weakens the adsorption of the interfacial water molecules, and inhibits proton transport, which also realizes the inhibition of HER and improves the selectivity of NRR. This study highlights that limiting the slow electron transport strategy may inform the advancement of efficient and highly selective electrocatalysts.