Dynamic Stress Enhances Electrocatalytic Hydrogen Evolution Reaction on Metals

Catalysts are a key enabling technology in the energy transition but are inherently limited in static operation. Strain is known to enhance catalytic performance by changing the electronic and geometric structure of active sites. Dynamically straining a catalyst can theoretically boost catalytic performance above the inherent limits of static catalysis. However, current approaches are not able to induce strain at the intermediate frequencies (10-1000 Hz) required to achieve this. In this study, we present a method to dynamically stress catalyst bodies at frequencies up to 1000 Hz using piezoelectric actuators. We demonstrate enhanced catalytic performance using dynamic stress in the hydrogen evolution reaction (HER) over metal foil electrodes, such as Cu, Pt, and Ni. We show that the HER current depends on the applied vibration frequency, intensity and duty cycle, and we introduce Mechano-Electrochemical Spectroscopy (MES) as a method to study the effect of dynamic stress on electrocatalytic performance. The current obtained under dynamic stress peaked at specific applied vibrational frequencies, reaching values up to 30 times the current under static operation on anodized Cu electrodes. Such peaks cannot be understood according to current resonant catalysis theory. Our results demonstrate that the phenomenon is due to faster electron transfer kinetics, and to strain amplification at certain frequencies for which the vertical vibration velocity in the catalyst is maximized, as shown by operando Laser Doppler Vibrometry (LDV). Being able to modulate surface strain over time holds the promise to form catalytic ratchets, which can in principle promote chemical reactions beyond static thermodynamic equilibrium, and steer catalytic selectivity to a desired product. We believe that this method has potential impact on developing better catalytic technologies in a number of (electro)chemical reactions for more sustainable chemical production.