Combinatorial Screening of Bimetallic Electrocatalysts for Nitrogen Reduction to Ammonia Using a High-Throughput Gas Diffusion Electrode Cell Design

Abstract

The electrochemical nitrogen reduction reaction (NRR) is a promising alternative to the current greenhouse-gas-emission intensive process to produce ammonia (NH3) from nitrogen (N2). However, finding an electrocatalyst that promotes NRR over the competing hydrogen evolution reaction (HER) has proven to be difficult. This difficulty could potentially be addressed by accelerating the electrocatalyst development for NRR by orders of magnitude using high-throughput (HTP) workflows. In this work, we developed a HTP gas diffusion electrode (GDE) cell to screen up to 16 electrocatalysts in parallel. The key innovation of the cell is the use of expanded Polytetrafluoroethylene (ePTFE) gas diffusion layers (GDL) which simplifies the handling of catalyst arrays compared to carbon fabrics and enables sufficient N2 mass transport. We demonstrate the robustness of the HTP workflow by screening 528 bimetallic catalysts of composition AB (A,B = Ag, Al, Au, Co, Cu, Fe, Mn , Mo, Ni, Pd, Re, Ru, W) for NRR activity. None of the materials produced ammonia significantly over background level which emphasizes the difficulty of finding active electrocatalysts for NRR and narrows down the search space for future studies.

Accelerated screening of gas diffusion electrodes for carbon dioxide reduction

“…15,16 Building upon these concepts, high throughput screening of GDEs for the electroreduction of dinitrogen was demonstrated with a 16-channel parallel testing system. 17 In the present work, we demonstrate an instrument that automates GDE cell assembly and screening in a manner suitable for future incorporation in a MAP via integration with robotic synthesis and GDE sample exchange. We are not aware of comparable hardware for automating the operation of a GDE electrochemical cell for incorporation into a MAP.…”

“…15,16 Building upon these concepts, high throughput screening of GDEs for the electroreduction of dinitrogen was demonstrated with a 16-channel parallel testing system. 17…”

Effect of Temperature and H Flux on the NH3 Synthesis via Electrochemical Hydrogen Permeation

“…Electrocatalytic ammonia synthesis from dinitrogen (N 2 ) reduction is currently regarded as a potential alternative to the current energy intensive and environmentally impactful, fossil fuel powered, Haber‐Bosch process [1–4] . Conventional aqueous electrochemical NH 3 synthesis appears extremely challenging, and the field is plagued with unreproducible results, due to mainly ammonia and nitrate impurity traces that obscure the dinitrogen reduction [5–11] …”

“…[1][2][3][4] Conventional aqueous electrochemical NH 3 synthesis appears extremely challenging, and the field is plagued with unreproducible results, due to mainly ammonia and nitrate impurity traces that obscure the dinitrogen reduction. [5][6][7][8][9][10][11] Alternatively, an unconventional approach, based on hydrogen permeable electrodes, has been proven to be an attractive solution for the production of NH 3 from dinitrogen and water at ambient conditions [12] (D. Ripepi, PhD thesis, Delft University of Technology (NL), 2023; DOI: 10.4233/uuid:e75408f4-b1f3-446a-bfd5-19d9465f7038. This method uses a solid, non-porous, metal electrode to physically separate the electrochemical hydrogen generation from the catalytic dinitrogen activation and hydrogenation to ammonia.…”

Non-idealities in CO2 electroreduction mechanisms revealed by automation-assisted kinetic analysis

“…Parallelization is another strategy, where arrays of different metal compositions or electrolyte conditions are tested simultaneously. [23][24][25] Parallel setups often do allow for product quantification, but quantification is typically performed either by aggregating effluents from multiple reactors or by manual work-up after electrolysis. An automated kinetic analysis workflow would ideally involve online product quantification of individual electrochemical cells, which is possible but likely to be expensive in a parallel configuration.…”