Using first principles to predict bimetallic catalysts for the ammonia decomposition reaction

Abstract

The facile decomposition of ammonia to produce hydrogen is critical to its use as a hydrogen storage medium in a hydrogen economy, and although ruthenium shows good activity for catalysing this process, its expense and scarcity are prohibitive to large-scale commercialization. The need to develop alternative catalysts has been addressed here, using microkinetic modelling combined with density functional studies to identify suitable monolayer bimetallic (surface or subsurface) catalysts based on nitrogen binding energies. The Ni-Pt-Pt(111) surface, with one monolayer of Ni atoms residing on a Pt(111) substrate, was predicted to be a catalytically active surface. This was verified using temperature-programmed desorption and high-resolution electron energy loss spectroscopy experiments. The results reported here provide a framework for complex catalyst discovery. They also demonstrate the critical importance of combining theoretical and experimental approaches for identifying desirable monolayer bimetallic systems when the surface properties are not a linear function of the parent metals.

H2 Production via Ammonia Decomposition Using Non-Noble Metal Catalysts: A Review

“…The adsorbed ammonia molecule undergoes successive N-H bond cleavage, releasing hydrogen atoms than can combine to form molecular hydrogen. The final step involves the recombinative desorption of nitrogen adatoms to yield molecular nitrogen [22]. Interestingly, even though the decomposition of ammonia is the reverse of the synthesis, catalyst do not necessarily exhibit the same activity in both directions due to a difference in rate limiting step as discussed in the work by Boisen et al [23].…”

“…The use of first principle calculations and interpolation across the periodic table has identified CoMo as an attractive bimetallic candidate to substitute ruthenium based catalysts for the production of hydrogen from ammonia [22,89,98]. As shown in Fig.…”

“…A requirement for bimetallic systems is a high stability under reaction conditions versus segregation into monometallic particles which would alter the surface properties and thus catalytic activity [22]. Additionally, in some supported bimetallic systems, the conditions of thermal treatment or high reaction temperatures can promote the formation of less reducible oxides such as Fe-Al, Co-Al, Ni-Al and Co-Si when supported on alumina or silica, resulting in considerably lower activity [88].…”

Understanding the electrocatalysis of oxygen reduction on platinum and its alloys

“…77 The volcano plot is a quantitative manifestation of Sabatier's principle and is widely used in both gas-phase heterogeneous catalysis and electrocatalysis. 28,55,68,[78][79][80][81][82][83][84][85][86][87] It is important to stress that the dashed line on the volcano plot in Fig. 5 represents an upper limit to the activity that we would expect for a metal surface.…”

Catalytic Ammonia Decomposition over High-Performance Ru/Graphene Nanocomposites for Efficient COx-Free Hydrogen Production

“…In this regard, the development of high-performance ammonia decomposition catalysts would be of significant importance for an ammonia-mediated hydrogen economy. Although research effort focused on the catalysis of ammonia decomposition has increased rapidly in recent years [21][22][23][24][25][26][27][28][29][30], and the catalytic activity of current catalysts still requires significant improvement because the current level of ammonia conversion remains much lower than the equilibrium, particularly at reaction temperatures lower than 400 • C. Research progress has identified that Ru is currently the most active component for ammonia decomposition. The control of Ru particles with optimal size and morphology is very important in ammonia decomposition since ammonia decomposition with Ru is structure-sensitive due to the variation of highly active B 5 -type sites [31,32].…”