Evaluation of Pt–Rh Nanoparticle–Based Electrodes for the Electrochemical Reduction of Nitrogen to Ammonia

Ammonia (NH 3 ) is one of the most used chemicals. Industrially, ammonia is produced by hydrogenation of N 2 through the Haber–Bosch process, a process in which enormous amounts of CO 2 are released and requires a huge energy consumption (~ 2% of the total global energy). Therefore, it is of paramount importance to explore more sustainable and environmentally friendly routes to produce NH 3 . The electrochemical nitrogen reduction reaction (NRR) to ammonia represents a promising alternative that is receiving great attention but still needs to be significantly improved to be economically competitive. In this work, the NRR is studied on Pt–Rh nanoparticle–based electrodes. Carbon-supported Pt–Rh nanoparticles (2–4 nm) with different Pt:Rh atomic compositions were synthesized and subsequently airbrushed onto carbon Toray paper to fabricate electrodes. The electrochemical NRR experiments were performed in a H-cell in 0.1 M Na 2 SO 4 solution. The results obtained show interesting faradaic efficiencies ( FE ) towards NH 3 which range between 5 and 23% and reasonable and reliable NH 3 yield values of about 4.5 µg h −1 mg cat −1 , depending on the atomic composition of the electrocatalysts and the metal loading. The electrodes also showed good stability and recyclability (constant FE and NH 3 yield in five consecutive experiments). Graphical Abstract Pt–Rh nanoparticle–based electrodes were employed for the NRR to NH 3 in 0.1 M Na 2 SO 4 . Interesting FE towards NH 3 and reasonable and reliable NH 3 yield values were observed depending on atomic composition and metal loading. Good stability and recyclability (constant FE and NH 3 yield in five consecutive experiments) were also observed.