Metal-free boron carbonitride with tunable boron Lewis acid sites for enhanced nitrogen electroreduction to ammonia

From a thermodynamic point of view, electrocatalytic nitrogen reduction reaction (NRR) is possible for the carbon-based metal-free catalysts, which are gradually becoming a class of potential alternatives to metal-based catalysts. However, the clarification of true active sites and corresponding exact catalytic mechanism of metal free catalysts is urgently required. Taking full advantage of boron Lewis acid, a series of boron carbonitride (BCN) materials were designed and synthesized and the Lewis acid catalysis sites were tuned easily by adjusting the relative contents of boron and nitrogen atoms. Boron-enriched BCN exhibited outstanding NRR performance with an ammonia yield of -8.39 mu g h(-1).cm(cat)(-1) (-41.9 mu g h(-1).mg(cat)(-1)) and Faradaic efficiency of -9.87 %, together with excellent stability. Density functional theory calculations indicate that the boron sites of BCN enable the low energy barrier of the NRR rate-determining steps and the spontaneity of nitrogen adsorption. Our philosophy opens a new possible avenue to explore high-performance metal-free materials for nitrogen activation.

Automated summary

Research has shown that boron carbonitride (BCN) materials can easily tune Lewis acid catalysis sites by adjusting the relative contents of boron and nitrogen atoms, exhibiting excellent electrocatalytic nitrogen reduction reaction (NRR) performance. This study opens up a new avenue for exploring high-performance metal-free materials for nitrogen activation.