The unprecedented ability of computations to probe atomic-level details of catalytic systems holds immense promise for the fundamentals-based bottom-up design of novel heterogeneous catalysts, which are at the heart of the chemical and energy sectors of industry. Here, we critically analyze recent advances in computational heterogeneous catalysis. First, we will survey the progress in electronic structure methods and atomistic catalyst models employed, which have enabled the catalysis community to build increasingly intricate, realistic, and accurate models of the active sites of supported transition-metal catalysts. We then review developments in microkinetic modeling, specifically mean-field microkinetic models and kinetic Monte Carlo simulations, which bridge the gap between nanoscale computational insights and macroscale experimental kinetics data with increasing fidelity. We finally review the advancements in theoretical methods for accelerating catalyst design and discovery. Throughout the review, we provide ample examples of applications, discuss remaining challenges, and provide our outlook for the near future.

The adsorption of atomic (H, C, N, O, S) and molecular (OH, CH x , NH x , CO, NO, CN, N2, HNO, NOH, HCN, x = 1–3) species at 1/4 monolayer coverage on an extended Ag(111) surface was studied using periodic density functional theory. Geometries and energies were calculated self-consistently using the PW91 functional; nonself-consistent energies using the RPBE functional are also provided. We analyze the binding energies, binding geometries, estimated diffusion barriers, harmonic vibrational frequencies, and energetic and geometric deformation parameters of these adsorbates, comparing them to experimental and theoretical results whenever possible. PW91 gives binding energies that match experimental binding energies more closely than RPBE, which consistently predicts weaker binding than PW91. The data were then used to construct and analyze thermochemistry-only potential energy pathways for the hydrocarbon-assisted and hydrogen-assisted selective catalytic reduction (SCR) of nitric oxide (NO). These analyses provide preliminary insights into the possible mechanistic paths of the SCR of NO on Ag(111). Specifically, we show that deep dehydrogenation leading to the formation of atomic intermediates is not favored on Ag(111).

Hydrogen bonding accelerates many catalytic reactions by orienting intermediates, stabilizing transition states, and even opening reaction pathways. However, most mechanistic studies regarding the decomposition of formic acid (FA), a promising hydrogen storage material, neglect hydrogen-bonding interactions even though FA is a strong hydrogen-bond donor and acceptor. Here, we probe the formation of bimolecular hydrogen-bonded complexes between FA and formate (FA–HCOO complexes) adsorbed on metal surfaces and how these complexes affect HCOO* decomposition. Using first-principles density functional theory (DFT) calculations on 12 close-packed (111)/(0001) and 8 open (100) surfaces of 12 transition metalsAg, Au, Co, Cu, Ir, Ni, Os, Re, Pd, Pt, Rh, and Ru, weshow that FA–HCOO complexes are generally thermodynamically stable, even at elevated temperatures and pressures. We then illustrate that these complexes produce infrared spectroscopic signatures consistent with as yet unassigned experimental peaks. We last demonstrate that by stabilizing the dangling bond of monodentate HCOO*, these complexes significantly lower the barriers for rotation of HCOO* from a bidentate to a monodentate configuration, the rate-limiting step for HCOO* decomposition on many surfaces. FA thus acts as a cocatalyst for HCOO* decomposition. Our results may guide the community toward improved catalysts for reactions involving HCOO* such as FA decomposition, methanol steam reforming, and the water gas shift reaction. More broadly, our work highlights the ability of hydrogen bonding to modify the adsorbed structures of intermediates and lower the barriers for their reaction on heterogeneous catalysts. This phenomenon can be relevant for other reactions involving ammonia, alcohols, and carboxylic acids.

Formic acid (HCOOH or FA) is a clean, safe, and renewable hydrogen storage material. Although Au catalysts decompose vapor-phase FA with high activity and selectivity towards hydrogen, the active site and reaction mechanism remain unclear. Here, we show that the subnanometric Au18 cluster (0.8 nm in diameter) is likely the active species for FA decomposition. We performed coverage self-consistent, density functional theory-based kinetic Monte Carlo simulations of FA decomposition on gas-phase Au18 clusters, predicting 100% selectivity towards hydrogen and turnover frequencies close to experimentally determined values. The active site is made up of a triangular ensemble of three atoms each possessing a coordination number of 5. Although there are two active site ensembles on the Au18 cluster, their occupations are strongly correlated due to strong, stabilizing, interactions between pairs of open-shell adsorbates mediated by the superatomic nature of the cluster. Because the occupation of the active sites blocks the dissociation of additional HCOOH molecules, there is kinetic isolation between turnovers: only one HCOOH molecule can dissociate on the cluster at a time. This explains the extraordinary, experimentally-2 observed selectivity of Au catalysts towards HD during decomposition of HCOOD and DCOOH. Our work offers nanoscale insights into the reaction mechanisms of FA decomposition over Au. To our knowledge, this represents the first example of heterogeneous catalysis by a cluster that catalyzes reactants one molecule at a time. Our work on Au18 thus sheds light on how the unique electronic properties of subnanometric clusters can be used to design quasi-molecular catalysts with high activity and selectivity.

AC O 2-mediated hydrogen storage energy cycle is ap romising wayt oi mplement ah ydrogen economy,b ut the exploration of efficient catalysts to achieve this process remains challenging.H erein, sub-nanometer Pd-Mn clusters were encaged within silicalite-1 (S-1) zeolites by al igand-protected method under direct hydrothermal conditions.T he obtained zeolite-encaged metallic nanocatalysts exhibited extraordinary catalytic activity and durability in both CO 2 hydrogenation into formate and formic acid (FA) dehydrogenation backt oC O 2 and hydrogen. Thanks to the formation of ultrasmall metal clusters and the synergic effect of bimetallic components,t he PdMn 0.6 @S-1 catalyst afforded af ormate generation rate of 2151 mol formate mol Pd À1 h À1 at 353 K, and an initial turnover frequency of 6860 mol H 2 mol Pd À1 h À1 for CO-free FA decomposition at 333 Kw ithout any additive.B oth values represent the top levels among state-of-the-art heterogeneous catalysts under similar conditions.This work demonstrates that zeoliteencaged metallic catalysts hold great promise to realizeC O 2mediated hydrogen energy cycles in the future that feature fast charge and release kinetics.