Ammonia is a widely produced chemical that is the basis of most fertilisers. However, it is currently derived from fossil fuels and there is an urgent need to develop sustainable approaches to its production. Ammonia is also being considered as a renewable energy carrier, allowing efficient storage and transportation of renewables. For these reasons, the electrochemical nitrogen reduction reaction (NRR) is currently being intensely investigated as the basis for future mass production of ammonia from renewables. This Perspective critiques current steps and miss-steps towards this important goal in terms of experimental methodology and catalyst selection, proposing a protocol for rigorous experimentation. We discuss the issue of catalyst selectivity and the approaches to promoting the NRR over H 2 production. Finally, we translate these mechanistic discussions, and the key metrics being pursued in the field, into the bigger picture of ammonia production by other sustainable processes, discussing benchmarks by which NRR progress can be assessed.

Ammonia is of emerging interest as a liquefied, renewable-energy-sourced energy carrier for global use in the future. Electrochemical reduction of N2 (NRR) is widely recognised as an alternative to the traditional Haber–Bosch production process for ammonia. However, though the challenges of NRR experiments have become better understood, the reported rates are often too low to be convincing that reduction of the highly unreactive N2 molecule has actually been achieved. This perspective critically reassesses a wide range of the NRR reports, describes experimental case studies of potential origins of false-positives, and presents an updated, simplified experimental protocol dealing with the recently emerging issues.

Ammonia (NH3) is a globally important commodity for fertilizer production, but its synthesis by the Haber-Bosch process causes substantial emissions of carbon dioxide. Alternative, zero-carbon emission NH3 synthesis methods being explored include the promising electrochemical lithium-mediated nitrogen reduction reaction, which has nonetheless required sacrificial sources of protons. In this study, a phosphonium salt is introduced as a proton shuttle to help resolve this limitation. The salt also provides additional ionic conductivity, enabling high NH3 production rates of 53 ± 1 nanomoles per second per square centimeter at 69 ± 1% faradaic efficiency in 20-hour experiments under 0.5-bar hydrogen and 19.5-bar nitrogen. Continuous operation for more than 3 days is demonstrated.