Comment by hnmullany
Here is an overview I wrote of next generation methods for ammonia synthesis:
https://www.linkedin.com/pulse/climatetech-134-de-carbonizin...
(FWIW - there are many many promising lab results that turn out to be false positives because the researchers did a bad job of controlling potential contamination in their ammonia measurements. Low concentrations of ammonia are everywhere, and you have to do a really good job making sure you're not measuring background levels vs. what you think you're producing)