Researchers from the Chinese Academy of Sciences propose a new strategy to develop high-performance electrocatalysts for ammonia synthesis.
Highly efficient synthesis of ammonia under ambient temperatures and pressures has been drawing increasing attention for wide applications of scientists and industries around the world. Developing highly active and selective materials with transformative catalytic performance for ammonia synthesis is still a giant challenge.
Atomic catalysts have long been the research frontier in the field of catalysis because of their unique structures and properties, such as the high atom utilization efficiency, high reaction selectivity and activity. Compared to the traditional single-atom catalysts, graphdiyne-based metal atomic catalysts feature unique and well-defined chemical and electronic structures, highly catalytic activity and selectivity, which is expected to achieve high selectivity and high yield of ammonia under ambient temperatures and pressures.
Recently, by utilizing the unique properties of graphdiyne, Professor Li Yuliang and a team from the Chinese Academy of Sciences published a research paper in National Science Review, proposing a new metal ion anchoring-electron transfer-self-reduction strategy for anchoring zero-valent palladium atoms. A free-standing 3D zero-valent atomic catalyst electrode was fabricated and showed high performance in electrocatalysis conversion of nitrogen to ammonia reaction at ambient conditions.
The scanning electron microscopy (SEM), high resolution transmission electron microscopy (TEM), aberration corrected high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM), X-ray near-edge absorption structure (XANES) and extended X-ray absorption fine structure spectrum (EXAFS) results solidly demonstrated that the palladium atoms individually anchored on graphdiyne and exhibited zero-valence state.
This catalyst shows unique advantages such as determined electronic and chemical structure, determined active sites, clear reaction mechanism and process, excellent properties and performance. For example, in neutral conditions, the palladium-graphdiyne catalyst has the highest ammonia yield nearly ten times higher than the reported materials. Under acidic conditions, its catalytic activity can also reach much higher levels. The 15N isotope labelling experiments confirmed that the ammonia was formed from the reduction of nitrogen, revealing that the palladium-graphdiyne catalyst is highly selective and active toward ammonia synthesis. Moreover, both the ammonia production rate and Faradaic efficiency of the catalyst can be maintained for several cycles without decay, confirming its robust stability. [APBN]