Hypes and hopes on the materials development strategies to produce ammonia at mild conditions: International Journal of Hydrogen Energy

The conventional Haber-Bosch (HB) process is the mainstream route to manufacture ammonia (NH3); the latter being one of the most significant compounds and a carbon-free energy carrier; HB operates at high pressure and temperature, resulting in significant energy consumption and CO2 emissions. An alternative method that has lately received a lot of attention is the electrocatalytic nitrogen reduction reaction (NRR), which produces NH3 in ambient settings using renewable energy. The rate of NH3 synthesis and faradaic efficiency (FE) are both used as catalytic activity descriptors; their values decreased when the competing hydrogen evolution reaction (HER) is picking up. The design of high-performance NRR catalysts, operating under ambient settings, while suppressing HER, is a major research field in the energy sector. This review discusses recent progress on catalyst design, as well as challenges and opportunities on the catalytic NH3 synthesis pathways focusing on different classes of materials, such as Ru-based catalysts, inorganic metal oxides, organic covalent-organic frameworks (COFs), and metal-organic frameworks (MOFs). Experimental validation studies on the NRR, through isotopic studies, are presented as well as future directions for the most prominent catalytic substrates. © 2023 Hydrogen Energy Publications LLC