Recently, the research team led by Professor Xiaoxiang Heng from Wuhan University published their latest research findings on electronic structure tuning for interface catalytic hydrogenation in both Nature Communications and Advanced Materials.
In recent years, significant progress has been made in the study of catalysts for electrocatalytic hydrogenation, leading to continuous improvement in efficiency. However, due to inherent physical barriers at the solid-liquid interface and limitations in research methods, there still lacks a systematic and clear understanding of the dynamic evolution of active surface electronic structures and micro-coordination of active sites.
In response, researchers focused on the strong proton-coupling phenomenon on metal catalytic surfaces during electroreduction. Utilizing various in-situ spectroscopic characterization techniques, they demonstrated the existence of strong proton-coupling effects. It was shown that active surfaces represented by Pd would in-situ form PdHx catalytic reaction centers.
Compared to other active metal surfaces, the relatively strong hybridization of d(Pd)-p(N) orbitals filled the electronic states of the N-based reaction group's antibonding orbitals, enhancing the ability of the initial hydrogenation step of the reaction group C≡N. Additionally, the presence of hydrogen atoms in the lattice reduced the d orbitals of Pd, weakening the desorption barrier of the target product (ethylamine), facilitating adsorption-desorption equilibrium during the catalytic reaction process. Due to the appropriate continuous band position of Pd-based catalysts, they exhibited excellent hydrogenation reaction activity and product selectivity among the screened series of metal catalysts. Furthermore, researchers expanded their studies to verify the feasibility of electrocatalytic hydrogenation of acetonitrile using proton exchange membrane electrolyzers. Test results showed that at a current density of 200 mA cm^2, Pd/C exhibited significantly higher ethylamine Faraday efficiency and turnover frequency compared to other screened metal catalysts, with an order of magnitude difference.
Additionally, the research team focused on the localized field regulation of non-polar N2 molecules and carried out a series of studies. Electrocatalytic nitrogen reduction reaction (NRR) for ammonia (NH3) synthesis is a green and sustainable reaction with the potential to supplement the industrial Haber process. However, N2, as an inert non-polar molecule, is difficult to adsorb on the electrode surface and further activate, greatly limiting the selectivity and activity of NH3 synthesis. Although various external stimuli (such as pressure, temperature, light) have been reported to regulate gas molecule adsorption, there is still a lack of systematic research on the localized regulation of molecule adsorption through surface electrostatic fields. When the surface electrostatic field of the electrode changes from uniform distribution to localized polarization, the charge on the high-curvature part of the electrode surface becomes more concentrated due to the existence of the tip effect, thereby attracting non-polar molecules. More importantly, such unevenly polarized electric fields can further stabilize charged groups and achieve rapid charge conduction and transport.
In this work, the authors propose enhancing the adsorption activation capability of N2 by surface localized polarization electric fields through atomic doping engineering. They detected the adsorption state of N2 (enhanced effect of polarized electric fields) through in-situ Fourier transform infrared spectroscopy based on a synchrotron light source, ultimately achieving efficient acidic NRR processes.
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