Multistrategy Optimization for Mo-Doped Ni3S2 as an Efficient Catalyst in Selective Amine-to-Nitrile Conversion Coupled with Hydrogen Generation

Abstract

The electrooxidation of amines to nitriles (AOR) offers a promising alternative to the oxygen evolution reaction (OER) for energy-saving hydrogen production coupled with value-added synthesis. However, simultaneously achieving high activity, selectivity, and OER suppression remains a key challenge. Herein, we demonstrate a multistrategy optimization approach for efficient propylamine electrooxidation reaction by synergistically tailoring catalyst properties and electrolyte composition. We first develop a Mo-doped Ni3S2 electrocatalyst (Mo-Ni3S2), where Mo doping performs dual functions: electronically modulating Ni sites to generate high-valence active centers for dehydrogenation and inducing the generation of surface SO42− groups. These groups create a negatively charged interface that enriches amine reactants while repelling hydroxyl species, thereby suppressing OER. As a second important strategy, the electrolyte (0.4 M KOH + 0.1 M Na2SO4) was engineered to effectively suppress product hydrolysis. This integrated approach enables the optimized system to deliver exceptional performance: ultrahigh activity (Tafel slope of 20.9 mV dec−1), ≥97% Faradaic efficiency for propionitrile at 90 mA cm−2, and high reaction selectivity. When coupled with the hydrogen evolution reaction (HER) in a two-electrode system, the AOR||HER electrolyzer requires only 1.42 V to reach 10 mA·cm−2 (vs 1.63 V for OER||HER); in an H-cell at 90 mA·cm−2, the H2 Faradaic efficiency remains 98−99%, while the propionitrile FE decreases from 95% at 1.45 V to 80% at 1.65 V, establishing a viable paradigm for coproducing hydrogen and valuable nitriles.