Density Functional Theory Analysis of a Cuag Catalyst for Increasing Selectivity in Electrocatalytic Urea Synthesis
2025 AIChE Annual Meeting
Density Functional Theory Analysis of a Cuag Catalyst for Increasing Selectivity in Electrocatalytic Urea Synthesis
Despite their high energy demands, the Haber-Bosch and Bosch-Meiser processes dominate industrial urea (H2NCONH2) synthesis. The Haber-Bosch process alone accounts for roughly 2% of global energy expenditure and 1% of carbon dioxide (CO2) emissions. Approximately half of the ammonia produced by Haber-Bosch is used to synthesize urea in the Bosch-Meiser process. Prior work estimates the global warming potential of synthetic urea as roughly 0.7 tons of CO2-equivalent emissions per metric ton of urea. Electrochemical co-reduction of nitrate (NO3-) and CO2 offers a sustainable alternative, recycling major air and water pollutants and reducing fossil fuel consumption. However, current catalysts suffer from poor selectivity. Copper–silver thin films are being investigated in this work as a potential catalyst to promote efficient urea synthesis through early C-N coupling. Prior work indicates copper is an optimal catalyst for reducing nitrates towards ammonia. Silver has been shown to weakly coordinate with carbon dioxide, limiting reduction to carbon monoxide. Together, these two pathways motivate the hypothesis that a copper–silver alloy could promote early carbon–nitrogen bond formation and increase reaction efficiency.
We use density functional theory to compare free energy trends for theorized intermediates on copper-silver versus pure copper catalysts. Calculations employ the Grid-based Projector Augmented-Wave (GPAW) method using revised Perdew-Burke-Ernzerhof (RPBE) functionals. Applied potentials are modeled using the Solvated Jellium method (SJM). Geometry optimization and energy convergence are performed for CO2, NO3-, H2NCONH2, and proposed intermediates. Computational testing of free energy trends for intermediates adsorbed to a pure copper catalyst is ongoing. The results, to be presented, are expected to reveal energy barriers and preferred mechanisms for C-N bond formation on the reference catalyst. Future work will extend the computational methods to CuAg catalysts, comparing energy barriers and preferred mechanisms. These insights will inform ongoing efforts to design copper-silver-based catalysts in CO2 and NO3- co-reduction processes.
