Producing fuels and chemicals using electricity has drawn considerable interest in recent decades. To date, research in electrocatalysis – the key tool which allows us to link electricity to chemical reactions – remains strongly focused on the transformation of small inorganic molecules such as CO2, H2O, N2, and oxygenated biomass derivatives. Yet, comprehensive industrial electrification will likely require electrocatalytic methods that can promote the reactions that make up the core of the chemicals and fuels industry: n-alkane transformations.
In this talk, I will demonstrate that electricity-driven alkane transformations not only are feasible but that they also unlock new avenues of reactivity, offering solutions to long-standing challenges in catalytic alkane chemistry. Specifically, I will show how our group combined a fundamental understanding of interfacial electrocatalytic processes1 with in-situ electrochemical mass spectrometry to gain independent, real-time control over the elementary steps of alkane transformations at room temperature. By modulating the potential applied to an electrocatalyst surface, we were able to independently control the adsorption of n-alkanes, initiate the transformation of adsorbates while they are bound to the surface, and selectively desorb desired products while keeping others anchored. These methods provide a powerful lever of control over catalytic surface chemistry, enabling us to demonstrate remarkable reactivity, including: (1) the room-temperature electrochemical fragmentation of ethane2 and butane3 into shorter chain fragments, and (2) the room-temperature dehydrogenation of n alkanes to alkenes.4 Beyond these transformations, I will show how leveraging independent control over elementary steps allowed us to deconstruct the continuous oxidation of n-alkanes in fuel cells into its fundamental steps—identifying bottlenecks and providing new design principles for improved catalysts.5
In the final part of my talk, I will discuss how, at a fundamental level, applied voltages control the rate of electrocatalytic reactions. Electron transfer reactions are typically thought to pass through a vibrationally activated transition state, making them temperature dependent. However, we discovered that some electrocatalytic reaction classes, for example CO₂ reduction, show little to no temperature dependence, regardless of the catalyst or electrolyte. Building on previous reports by Halpern and Conway, I will discuss how our mechanistic interpretation of this phenomenon points to the translational, rather than vibrational, reorganization of electrolyte components to form an interfacial electron transfer transition state.6 I will also discuss how this insight highlights the importance of considering more than enthalpic activation barriers in designing electrocatalytic systems.
By extending electrocatalysis to alkane transformations and uncovering new mechanistic insights into reaction rate control, we aim to enable more precise atomic-level manipulation in electrocatalytic processes, paving the way for a more selective, efficient, and electrified chemical industry of the future.