The origin of the large kinetic pH effect in hydrogen electrocatalysis, that is, the approximately two orders of magnitude decrease in reaction kinetics when moving from acid to alkaline, remains far from having a consensus. Here we show that it is the significantly different connectivity of hydrogen-bond networks in electric double layers that causes the large kinetic pH effect. This result has been obtained by meticulously comparing the electric double layers of acid and alkaline interfaces from ab initio molecular dynamics simulations, and the computed vibrational density of states of water molecules in the interfaces simulated with ab initio molecular dynamics, with the results of in situ surface-enhanced infrared absorption spectroscopy. Using a Pt–Ru alloy as a model catalyst, we further reveal an unanticipated role of OH adsorption in improving the kinetics of alkaline hydrogen electrocatalysis, namely, by increasing the connectivity of hydrogen-bond networks in electric double layers rather than by merely affecting the energetics of surface reaction steps. These findings highlight the key roles of electric double layer structures in electrocatalysis.
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Representative data and extended datasets that support the findings reported in this study are available in the manuscript and the Supplementary Information. The data in the figures shown in the main text and the atomic coordinates of the initial and final configurations of the trajectories in the AIMD simulations are provided as supplementary files. Additional data are available from the corresponding author upon reasonable request.
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We gratefully acknowledge the financial support from the National Natural Science Foundation of China (grant nos 21832004 and 21673163 to S.C.) and C.-L. Guo at Wuhan University for fruitful discussions and kindly sharing the infrared spectrometer. We also gratefully acknowledge generous grants of computational resources from the Supercomputing Center of Wuhan University.
The authors declare no competing interests.
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Supplementary Figs. 1–33 and Notes 1–3.
Supplementary Data 1
Atomic coordinates of the initial and final configurations of the trajectories in AIMD simulations for the systems shown in Fig. 1 and Fig. 5 (in Vienna Ab initio Simulation Package CONTCAR format).
Supplementary Data 2
Data shown in Figs. 1–5.
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Li, P., Jiang, Y., Hu, Y. et al. Hydrogen bond network connectivity in the electric double layer dominates the kinetic pH effect in hydrogen electrocatalysis on Pt. Nat Catal 5, 900–911 (2022). https://doi.org/10.1038/s41929-022-00846-8