Recent progress towards mild-condition ammonia synthesis

Ammonia is essential for food and energy. Industrial ammonia synthesis via Haber–Bosch process is energy-intensive and releases large amount of CO2. Increasing research efforts are devoted to “green” ammonia synthesis. The present article reviews the recent progress in the fields of thermocatalytic, electrocatalytic, photocatalytic and chemical looping processes for dinitrogen reduction towards ammonia formation and discusses the challenges borne for mild-condition synthesis.