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The increasing interest in utilizing methane, the primary component of natural gas, for chemical production has spurred research into methane partial oxidation (MPO) as an alternative to traditional steam methane reforming (SMR). MPO has lower energy requirements and potential for carbon capture, making it an attractive option for hydrogen production. Challenges remain, however, such as carbon deposition leading to degradation and achieving high hydrogen selectivity. Here, the impact of periodic reactor operation on MPO over a Pt/Al2O3 catalyst was studied, primarily via varying reactor inlet compositions. Experiments were conducted using periodic operation strategies to assess the influence of changing reactant inlet concentrations on hydrogen formation during MPO. The results suggest that cycling between mixtures with low and high oxygen content can lead to transient hydrogen formation rates that surpass those achieved at steady state. Control experiments and density functional theory (DFT) calculations show that enhanced hydrogen formation can be attributed to the reaction between CO with hydroxyl groups at the metal and alumina support interface. This work underscores the critical role of surface coverages at the metal support interface and suggests avenues for future exploration, including alternative support materials with higher OH mobility and changes in the cycling scheme to enhance catalyst performance under periodic conditions. 

Hydrogen gas is a promising renewable energy storage medium when produced via water electrolysis, but this process is limited by the sluggish kinetics of the anodic oxygen evolution reaction (OER). Herein, we used a microkinetic model to investigate promoting the OER using programmable oxide catalysts (i.e., forced catalyst dynamics). We found that programmable catalysts could increase current density at a fixed overpotential (100-600× over static rates) or reduce the overpotential required to reach a fixed current density of 10 mA cm-2 (45-140% reduction vs static). In our kinetic parametrization, the key parameters controlling the quality of the catalytic ratchet were the O*-to-OOH* and O*-to-OH* activation barriers. Our findings indicate that programmable catalysts may be a viable strategy for accelerating the OER or enabling lower-overpotential operation, but a more accurate kinetic parametrization is required for precise predictions of performance, ratchet quality, and resulting energy efficiency. 

Hydrogen spillover involves the migration of H atom equivalents from metal nanoparticles to a support. While well documented, H spillover is poorly understood and largely unquantified. Here we measure weak, reversible H2 adsorption on Au/TiO2 catalysts, and extract the surface concentration of spilled-over hydrogen. The spillover species (H*) is best described as a loosely coupled proton/electron pair distributed across the titania surface hydroxyls. In stark contrast to traditional gas adsorption systems, H* adsorption increases with temperature. This unexpected adsorption behaviour has two origins. First, entropically favourable adsorption results from high proton mobility and configurational surface entropy. Second, the number of spillover sites increases with temperature, due to increasing hydroxyl acid–base equilibrium constants. Increased H* adsorption correlates with the associated changes in titania surface zwitterion concentration. This study provides a quantitative assessment of how hydroxyl surface chemistry impacts spillover thermodynamics, and contributes to the general understanding of spillover phenomena.