Efficacy of Methylammonium Iodobismuthate: A Green Catalyst for Reduction of Nitrate to Ammonia.

Ammonia (NH₃) is vital in agriculture and industry, yet its large-scale production remains energy-intensive and environmentally hostile. Herein, for the first time we report the development of lead-free nontoxic hexagonal methylammonium iodobismuthate metal halide perovskite (MABI) as a highly efficient and sustainable electrocatalyst for green ammonia production from nitrate reduction. The unique structure of MABI, featuring an isolated BiI₆ octahedron stabilized by a methylammonium cation, offers a highly tunable electronic environment required for nitrogen activation and hydrogenation. The experimental and computational studies categorically established the formation of an interconnected pure hexagonal structure with a band gap of ∼2.1 eV. Electrocatalytic nitrate reduction revealed that MABI displays a remarkable ammonia yield (27.53 μg mg^-1 h^-1) with excellent stability and a quite impressive Faradaic efficiency (40%). This work highlights the potential of halide bismuthate perovskites as an alternative to traditional catalysts to produce ammonia in ambient conditions that address the dual challenges of energy efficiency and environmental sustainability.