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Selective partial oxidation of hydrocarbons to oxygenates plays a large role in the chemical industry, while falling prices for electricity from renewable sources make electrification of such industrial chemical processes relevant. The oxidation of propene is an interesting model system as propene can be oxidized in two different positions, allowing for insights into the reaction mechanism. On Pd, a layer of adsorbates formed in situ governs the reaction by steering reactant adsorption to achieve high selectivity for allyl oxidation, albeit largely inhibiting the reaction rate. Through rational catalyst design, we demonstrate that alloying reactive Pd with inert Au influences the adsorbate layer formation, enhancing activity while maintaining high selectivity toward allyl oxidation. We obtain mechanistic insights with a combination of ab initio computational modeling and electrochemical measurements with ex situ product quantification and online mass spectrometry. Using a statistical approach, we explore the correlation of the Au:Pd ratio with Pd surface cluster size and density, which determine the properties of the adsorbate layer and thus the reaction outcome. We report an activity enhancement by a factor 2.4 with 10% Au in Pd and propose that (i) activity is maximized at potentials just before Pd cluster oxidation and (ii) the optimal catalyst surface contains approximately one Au every six Pd atoms, statistically most frequent at the nominal alloy composition Au14Pd86.

This contribution reports the discovery and analysis of a p-block Sn-based catalyst for the electroreduction of molecular oxygen in acidic conditions at fuel cell cathodes; the catalyst is free of platinum-group metals and contains single-metal-atom actives sites coordinated by nitrogen. The prepared SnNC catalysts meet and exceed state-of-the-art FeNC catalysts in terms of intrinsic catalytic turn-over frequency and hydrogen–air fuel cell power density. The SnNC-NH3 catalysts displayed a 40–50% higher current density than FeNC-NH3 at cell voltages below 0.7 V. Additional benefits include a highly favourable selectivity for the four-electron reduction pathway and a Fenton-inactive character of Sn. A range of analytical techniques combined with density functional theory calculations indicate that stannic Sn(iv)Nx single-metal sites with moderate oxygen chemisorption properties and low pyridinic N coordination numbers act as catalytically active moieties. The superior proton-exchange membrane fuel cell performance of SnNC cathode catalysts under realistic, hydrogen–air fuel cell conditions, particularly after NH3 activation treatment, makes them a promising alternative to today’s state-of-the-art Fe-based catalysts.

As the world reluctantly acknowledges the environmental drawbacks of a fossil fuelled economic growth, a rigorous scientic approach shall lead the transition of modern society towards a sustainable model of growth. The electrication of processes at dierent levels stands out as a promising solution to couple the everyday actions with the deployment of renewable energy generation and consumption. Electrocatalytic reactions lie at the core of many technologies that are essential for the transition, from energy storage and conversion to electrochemical production of commodity chemicals. This thesis investigates reactions in the panorama of electrocatalysis by coupling the computational framework of Density Functional Theory with state-of-the-art characterization techniques and electrochemical methods, capitalizing on the positive synergies between different research methodologies to attain fundamental atomistic insights on the interplay between catalyst surface and reactivity pathways. The work presented in this thesis is divided in two macro areas. The rst deals with the electrochemical upgrade of hydrocarbon feedstock to valuable partial oxidation products, focusing on the reaction of propene electro oxidation, an important transformation for the industrial chemical sector. Herein is reported a systematic, multi-angle study on propene selective electrochemical transformation to valuable allylic products (acrolein and acrylic acid) on a palladium electrode in acidic media. Through this study, specic reaction drivers are isolated and surface phenomena occurring under operative conditions are successfully correlated to the reaction observed outcome. Based on the insights achieved on palladium electrode, a catalyst design strategy is proposed where palladium is alloyed with inert gold to enhance the catalytic activity, maintaining selectivity to allylic oxidation products altogether. The catalytic performance is then rationalized through the developed theoretical model, a

The efficient partial oxidation of hydrocarbons to valuable chemicals without formation of CO2 is one of the great challenges in heterogeneous catalysis. The ever-decreasing cost of renewable electricity and the superior control over reactivity qualify electrochemistry as a particularly attractive means of addressing this challenge. Yet, to date, little is known about the factors regulating hydrocarbon oxidation at the atomic level. A relevant showcase reaction is propene electro-oxidation to key industrial commodity chemicals, such as acrolein, acrylic acid and propylene oxide. In this study, we investigate the partial electrochemical oxidation of propene on high-surface area Pd electrodes using a combination of electrochemical measurements, advanced product characterization and theoretical modeling. We report a new reaction product, propylene glycol, and high selectivity towards acrolein. We further identify key reaction intermediates and propose a mechanism dictated by the surface coverage of organic species formed in situ, where stable reactant adsorption at low coverage determines the selectivity towards allylic oxidation at high coverage. Our fundamental findings enable advances in partial hydrocarbon oxidation reactions by highlighting atomic surface structuring as the key to selective and versatile electrochemical catalyst design.

H2O2 is a valuable, environmentally friendly oxidizing agent, with a wide range of uses, from the provision of clean water to the synthesis of valuable chemicals. The on-site electrolytic production of H2O2 would bring the chemical to applications beyond its present reach. The successful commercialization of electrochemical H2O2 production requires cathode catalysts with high activity, selectivity and stability. In this Perspective, we highlight our current understanding of the factors that control the cathode performance. We review the influence of catalyst material, electrolyte and the structure of the interface at the mesoscopic scale. We provide original theoretical data on the role of the geometry of the active site and its influence on activity and selectivity. We have also conducted a series of original experiments on (i) the effect of pH on H2O2 production on glassy carbon, pure metals, and metal-mercury alloys, and (ii) the influence of cell geometry and mass transport in liquid half-cells in comparison to membrane electrode assemblies.