Renewable electron-driven bioinorganic nitrogen fixation: a superior route toward green ammonia?

Ammonia is crucial for the fertilizer industry and the global chemical economy. However, the conventional Haber-Bosch process for NH3 synthesis is energy and capital-intensive and associated with high greenhouse gas emissions (1.44% of global CO2 emissions). Thus, green ammonia synthesis that supports the green energy transition and sustainable development has become a research hotspot. Among others, nature-inspired bioelectrocatalytic nitrogen fixation (e-BNF), which combines the advantages of electrocatalysis, enzymes/microbes, and renewable energy, is emerging as one of the cutting-edge carbon-neutral, energy-efficient, and potentially sustainable strategies for ammonia synthesis. Nevertheless, the development of e-BNF is still in its infancy. Herein, we present a systematic assessment of the historical development and current state of e-BNF for ammonia synthesis. First, we revisit the conventional Haber-Bosch process and abiotic electrocatalysis approaches and access the fundamentals, merits, and challenges of bioinorganic e-BNF in the context of electrochemistry and bioelectrochemistry. Second, the electron transfer mechanisms, and enzyme- and microbial cell-based e-BNF are thoroughly discussed. At the end, we discuss future developments and perspectives on bioelectrocatalytic ammonia synthesis.