Selective Electrocatalytic Reduction of 3-Nitrostyrene to 3-Vinylanaline over Pd- and Pt- based Nanoparticles

Selective catalytic hydrogenation of organic molecules is one of the most critical processes in the fine chemical and pharmaceutical industries. Electrocatalytic hydrogenation (ECH) enables the controlled reduction of organic compounds under mild conditions with improved sustainability. This process requires high-performance electrocatalysts with satisfactory activity and selectivity. This study explores the use of Pd- and Pt-based alloy or intermetallic nanoparticles as electrocatalysts to enhance the selectivity and efficiency of 3-nitrostyrene (3-NS) conversion to 3-vinyl aniline (3-VA), a model reaction for the green chemical synthesis of functional aromatic amines. A critical challenge of electrochemical 3-NS-to-3-VA conversion is the selectivity of the desired products. Our hypothesis is controlling electrochemical reaction conditions (pH and potentials) and catalyst binding energies with reactants and intermediates could lead to improved selectivity. In our study, the electrocatalytic performances of commercial Pd and Pt catalysts were first evaluated using different pH conditions and reduction potentials, and we found that the neutral condition could achieve a higher selectivity at the same potential comparing to acidic or alkaline conditions. Furthermore, to enhance the selectivity to 3-VA rather than other deeply reduced products (3-ethylaniline (3-EA) and 1-ethyl-3-nitrobenzene (3-EN)), nanoparticles including CuPd, CoPt, Co2P and Co2P/Pt were studied, demonstrating the potential of alloying and heterostructure effects in weakening the adsorption energy of reaction intermediates and minimizing the formation of deeply reduced products. These catalysts enhanced selectivity for 3-VA, achieving over 80% at -0.45 V (vs. RHE), which were significantly better than monometallic and commercial Pt and Pd catalysts (< 40%). The future work will focus on further improvement of catalytic activity, selectivity and detailed characterization, like in situ analysis, to understand structural and compositional changes of the catalysts during the reaction. Computational work (e.g., DFT) will also be pursued to understand how the catalysts’ atomic structures influence the reaction pathways and performances. The efficacy of this technology for other functional amine production will also be investigated. These insights will aid in designing more efficient and selective electrocatalysts for the industrial production of functionalized aromatic amines.