Photoelectrocatalytic Nitrogen Reduction to Ammonia: a Review of Advanced Materials and Interface Engineering

Abstract

Ammonia is essential for fertilizers, chemicals, and emerging carbon-free energy systems, yet its conventional production relies on an energy-intensive process with substantial carbon dioxide emissions. Photoelectrocatalytic nitrogen reduction has emerged as a promising route for sustainable ammonia synthesis under mild conditions, combining solar light absorption with an electrochemical bias to activate the inert nitrogen molecule. This review examines recent progress in this field, focusing on the design of stable titanium dioxide-based photoanodes and selective photocathodes incorporating copper oxide and two-dimensional transition metal dichalcogenides such as molybdenum disulfide and tungsten disulfide. Synthesis strategies, fabrication methods, cell configurations, reaction mechanisms, and performance parameters are discussed. Key challenges, including the high activation barrier of nitrogen, competing hydrogen evolution, and nitrogen mass-transfer limitations, are analyzed alongside verification protocols and future directions for efficient, carbon-free ammonia production.