There has been a significant growth, from 2001-2021, in the publication volume of research towards the electrocatalytic or photocatalytic reduction of dinitrogen (Fig. ). In 2001, of publications investigating catalytic NRR, less than 1% were discussing photocatalytic or electrocatalytic nitrogen reduction. In 2021, publications discussing photocatalytic or electrocatalytic NRR grew to more than 25% of all catalytic NRR publications. Green ammonia synthesis was discussed primarily in journal publications with the number of patent documents reaching 20% of the total publication volume in 2020. The increased availability of green electricity likely leads to a preference for electrochemical methods for ammonia production. To analyze which fields of catalytic research may have been contributors to the growth in publications we investigated the catalysts that were discussed within these manuscripts over time (Fig. ). The number of distinct substances with a role in catalytic green ammonia synthesis have grown continuously from 2001 to 2021, indicating that the research area of photocatalytic or electrocatalytic is continuing to expand. The most recent four or five years have shown dramatic growth in substances, with less than 100 distinct substances in 2017 to nearly 500 distinct substances in 2021. Specific subsets of substance classes, such as inorganic materials (e.g. metal oxides), organic/inorganic small molecules, elements, and coordination compounds make up many of the new catalysts used in green ammonia synthesis.