Porous and Partially Dehydrogenated Fe2+-Containing Iron Oxyhydroxide Nanosheets for Efficient Electrochemical Nitrogen Reduction Reaction (ENRR)

The design and development of efficient catalysts for electrochemical nitrogen reduction reaction (ENRR) under ambient conditions are critical for the alternative ammonia (NH3) synthesis from N-2 and H2O, wherein iron-based electrocatalysts exhibit outstanding NH3 formation rate and Faradaic efficiency (FE). Here, the synthesis of porous and positively charged iron oxyhydroxide nanosheets by using layered ferrous hydroxide as a starting precursor, which undergoes topochemical oxidation, partial dehydrogenated reaction, and final delamination, is reported. As the electrocatalyst of ENRR, the obtained nanosheets with a monolayer thickness and 10-nm mesopores display exceptional NH3 yield rate (28.5 mu g h(-1) mg(cat.)(-1)) and FE (13.2%) at a potential of -0.4 V versus RHE in a phosphate buffered saline (PBS) electrolyte. The values are much higher than those of the undelaminated bulk iron oxyhydroxide. The larger specific surface area and positive charge of the nanosheets are beneficial for providing more exposed reactive sites as well as retarding hydrogen evolution reaction. This study highlights the rational control on the electronic structure and morphology of porous iron oxyhydroxide nanosheets, expanding the scope of developing non-precious iron-based highly efficient ENRR electrocatalysts.

Automated summary

A method for the synthesis of porous and positively charged iron oxyhydroxide nanosheets is reported, which involves the use of layered ferrous hydroxide as a starting precursor and undergoing topochemical oxidation, partial dehydrogenated reaction, and final delamination. As an electrocatalyst for electrochemical nitrogen reduction reaction (ENRR), the obtained nanosheets exhibit exceptional NH3 yield rate and Faradaic efficiency in a phosphate buffered saline (PBS) electrolyte. The study demonstrates the rational control on the electronic structure and morphology of porous iron oxyhydroxide nanosheets, expanding the development of efficient non-precious iron-based ENRR electrocatalysts.