Department of Chemistry, University of California, Davis, California, Davis, 95616, United States.
J Am Chem Soc. 2023 Feb 15;145(6):3419-3426. doi: 10.1021/jacs.2c10942. Epub 2023 Feb 3.
Pre-equilibrium reaction kinetics enable the overall rate of a catalytic reaction to be orders of magnitude faster than the rate-determining step. Herein, we demonstrate how pre-equilibrium kinetics can be applied to breaking the linear free-energy relationship (LFER) for electrocatalysis, leading to rate enhancement 5 orders of magnitude and lowering of overpotential to approximately thermoneutral. This approach is applied to pre-equilibrium formation of a metal-hydride intermediate to achieve fast formate formation rates from CO reduction without loss of selectivity (i.e., H evolution). Fast pre-equilibrium metal-hydride formation, at 10 M s, boosts the CO electroreduction to formate rate up to 296 s. Compared with molecular catalysts that have similar overpotential, this rate is enhanced by 5 orders of magnitude. As an alternative comparison, overpotential is lowered by ∼50 mV compared to catalysts with a similar rate. The principles elucidated here to obtain pre-equilibrium reaction kinetics via catalyst design are general. Design and development that builds on these principles should be possible in both molecular homogeneous and heterogeneous electrocatalysis.
预平衡反应动力学使催化反应的总速率比速率决定步骤快几个数量级。在此，我们展示了如何将预平衡动力学应用于打破电催化的线性自由能关系（LFER），从而将速率提高 5 个数量级，并将过电势降低到接近热中性。该方法应用于金属氢化物中间体的预平衡形成，以实现 CO 还原过程中快速形成甲酸盐，而不会损失选择性（即 H 析出）。快速的预平衡金属氢化物形成，在 10 M s 时，将 CO 电还原为甲酸盐的速率提高到 296 s。与具有相似过电势的分子催化剂相比，该速率提高了 5 个数量级。作为另一种比较，与具有相似速率的催化剂相比，过电势降低了约 50 mV。通过催化剂设计获得预平衡反应动力学的原理是通用的。基于这些原理的设计和开发应该可以在分子均相和异相电催化中实现。
