Role of CO* as a Spectator in CO₂ Electroreduction on RuO₂

RuO₂-based electrocatalysts are found to be active at low overpotential toward direct electrochemical reduction of CO₂ to formic acid and methanol. RuO₂ can circumvent the thermodynamic bottleneck resulting from the scaling relations observed on metallic electrocatalyst, by utilizing an alternate pathway through oxygen-coordinated intermediates. Employing density functional theory based computational electrocatalysis models we show adsorbate–adsorbate interaction effects for adsorbates and reaction intermediates on the RuO₂(110) surface are large and impactful to the reaction thermodynamics. We studied binding energy amendment due to adsorbate interaction (steric and electronic) with varying coverage of CO* spectators on the catalyst surface. Implications on the reaction pathways help us rationalize differences in experimentally observed carbonaceous product mix and suppression of the hydrogen evolution reaction (HER). We show that a moderate CO* coverage (∼50%) is necessary for obtaining methanol as a product and that higher CO* coverages leads to very low overpotential for formic acid evolution. Our analysis also clarifies the importance of the reaction condition for CO₂ reduction to liquid fuels utilizing RuO₂-based electrocatalysts

Unifying the 2e^– and 4e^– Reduction of Oxygen on Metal Surfaces

Understanding trends in selectivity is of paramount importance for multi-electron electrochemical reactions. The goal of this work is to address the issue of 2e^– versus 4e^– reduction of oxygen on metal surfaces. Using a detailed thermodynamic analysis based on density functional theory calculations, we show that to a first approximation an activity descriptor, Δ<i>G</i>_OH*, the free energy of adsorbed OH*, can be used to describe trends for the 2e^– and 4e^– reduction of oxygen. While the weak binding of OOH* on Au(111) makes it an unsuitable catalyst for the 4e^– reduction, this weak binding is optimal for the 2e^– reduction to H₂O₂. We find quite a remarkable agreement between the predictions of the model and experimental results spanning nearly 30 years

Graph Neural Network-Accelerated Multitasking Genetic Algorithm for Optimizing Pd_<i>x</i>Ti_1–<i>x</i>H_<i>y</i> Surfaces under Various CO₂ Reduction Reaction Conditions

Palladium (Pd) hydride-based catalysts have been reported to have excellent performance in the CO2 reduction reaction (CO2RR) and hydrogen evolution reaction (HER). Our previous work on doped PdH and Pd alloy hydrides showed that Ti-doped and Ti-alloyed Pd hydrides could improve the performance of the CO2 reduction reaction compared with pure Pd hydride. Compositions and chemical orderings of the surfaces with only one adsorbate under certain reaction conditions are linked to their stability, activity, and selectivity toward the CO2RR and HER, as shown in our previous work. In fact, various coverages, types, and mixtures of the adsorbates, as well as state variables such as temperature, pressure, applied potential, and chemical potential, could impact their stability, activity, and selectivity. However, these factors are usually fixed at common values to reduce the complexity of the structures and the complexity of the reaction conditions in most theoretical work. To address the complexities above and the huge search space, we apply a deep learning-assisted multitasking genetic algorithm to screen for PdxTi1–xHy surfaces containing multiple adsorbates for CO2RR under different reaction conditions. The ensemble deep learning model can greatly speed up the structure relaxations and retain a high accuracy and low uncertainty of the energy and forces. The multitasking genetic algorithm simultaneously finds globally stable surface structures under each reaction condition. Finally, 23 stable structures are screened out under different reaction conditions. Among these, Pd0.56Ti0.44H1.06 + 25%CO, Pd0.31Ti0.69H1.25 + 50%CO, Pd0.31Ti0.69H1.25 + 25%CO, and Pd0.88Ti0.12H1.06 + 25%CO are found to be very active for CO2RR and suitable to generate syngas consisting of CO and H2