Electrochemical hydrogenation of NO and CO: Differences and similarities from a computational standpoint

Electrolyzers can help in restoring the balance to the biogeochemical cycles of carbon and nitrogen while producing valuable chemical compounds. Before that happens on a global scale, various hurdles need to be overcome, some of which are related to the activity and selectivity of the materials used to catalyze electrolysis reactions. For instance, CO and NO are important electrolysis feedstocks and/or reaction intermediates and their hydrogenation is often energetically demanding. Here it is shown how the most favorable hydrogenation product among ∗CHO or ∗COH, and ∗NHO or ∗NOH on late transition metals can be ascertained by classification methods based on adsorption-energy scaling relations and “catalytic matrices”. In particular, late transition metals can be split into weak-binding and strong-binding and there is a noble-nonnoble energy gap between them. Such a simple categorization helps outline the metals and facets that selectively favor the making of O–H, C–H and N–H bonds.This work received financial support from grants PID2021-127957NB-I00 and TED2021-132550B–C21, which are funded by MCIN/AEI/10.13039/501100011033 and by the European Union

Designing water splitting catalysts using rules of thumb: advantages, dangers and alternatives

Thermodynamic analysis of the oxygen evolution reaction (OER) hints toward an intrinsic overpotential caused by the nonoptimal adsorption-energy scaling relation between OH and OOH. Consequently, nowadays it is a widely accepted yet unverified rule of thumb that breaking such scaling relation results in enhanced catalytic activity. In this Perspective, we show that breaking the OH-OOH scaling relation does not per se lower the OER overpotential. Instead, electrocatalytic symmetry and ease of optimization are shown to be key factors when screening for enhanced OER catalysts. The essence of electrocatalytic symmetry is captured by a descriptor called electrochemical-step symmetry index (ESSI). In turn, the ease of optimization and whether it should be scaling-based or scaling-free is provided by a procedure called delta−epsilon optimization. Finally, taking the search for bifunctional catalysts for oxygen electrocatalysis as an example, we show that the alternative analysis can be straightforwardly extended to other electrocatalytic reactions.This work was supported by Spanish MICIUN's RTI2018-095460-B-I00 and María de Maeztu MDM-2017-0767 grants and, in part, by Generalitat de Catalunya 2017SGR13, XRQTC grants and by COST Action 18234, supported by COST (European Cooperation in Science and Technology). F. C. V. thanks the Spanish MICIUN for a Ramón y Cajal research contract (RYC-2015-18996) and F. I. acknowledges additional support from the 2015 ICREA Academia Award for Excellence in University Research. O. P. thanks the Spanish MICIUN for an FPI PhD grant (PRE2018-083811). We are thankful to Red Española de Supercomputación (RES) for super-computing time at SCAYLE (projects QS-2019-3-0018, QS-2019-2-0023, and QCM-2019-1-0034). The use of supercomputing facilities at SURFsara was sponsored by NWO Physical Sciences

Evaluating Adsorbate–Solvent Interactions: Are Dispersion Corrections Necessary?

Incorporating solvent–adsorbate interactions is paramount in models of aqueous (electro)catalytic reactions. Although a number of techniques exist, they are either highly demanding in computational terms or inaccurate. Microsolvation offers a trade-off between accuracy and computational expenses. Here, we dissect a method to swiftly outline the first solvation shell of species adsorbed on transition-metal surfaces and assess their corresponding solvation energy. Interestingly, dispersion corrections are generally not needed in the model, but caution is to be exercised when water–water and water–adsorbate interactions are of similar magnitude.This work was supported by Grants PID2021-127957NB-I00, TED2021-132550B-C21, PID2021-126076NB-I00, CEX2021-001202-M, and MDM-2017-0767-20-1 funded by the Spanish MCIN/AEI/10.13039/501100011033 and the European Union. The authors also thank the Spanish “RES” for computational resources through Grants QHS-2022-1-0002 and QHS-2022-2-0016

How covalence breaks adsorption-energy scaling relations and solvation restores them

Catalysis and Surface Chemistr

Computational-experimental study of the onset potentials for CO2 reduction on polycrystalline and oxide-derived copper electrodes

The electrocatalytic reduction of CO2 (CO2RR) is a promising yet intricate process to alleviate the alarming imbalance in the carbon cycle. One of the intricacies of CO2RR is its structural sensitivity, which is illustrated by the varying onset potentials and selectivities of the reaction products depending on the electrode morphology. Here, using electrochemical real-time mass spectrometry (EC-RTMS), we accurately determine the onset potentials for seven CO2RR products including C1, C2, and C3 species on polycrystalline and oxide-derived Cu electrodes. Density functional theory calculations affordably including solvent and cation effects produce onset potentials of C2 species matching those obtained with EC-RTMS. Our analysis leads us to conclude that the elusive active sites at oxide-derived Cu, known to enhance ethanol production, are undercoordinated square ensembles of Cu atoms