Copper-based catalyst is uniquely positioned to catalyze the hydrocarbon formations through electrochemical CO₂ reduction. The catalyst design freedom is limited for alloying copper with H-affinitive elements represented by platinum group metals because the latter would easily drive the hydrogen evolution reaction to override CO₂ reduction. We report an adept design of anchoring atomically dispersed platinum group metal species on both polycrystalline and shape-controlled Cu catalysts, which now promote targeted CO₂ reduction reaction while frustrating the undesired hydrogen evolution reaction. Notably, alloys with similar metal formulations but comprising small platinum or palladium clusters would fail this objective. With an appreciable amount of CO-Pd₁ moieties on copper surfaces, facile CO^* hydrogenation to CHO^* or CO-CHO^* coupling is now viable as one of the main pathways on Cu(111) or Cu(100) to selectively produce CH₄ or C₂H₄ through Pd-Cu dual-site pathways. The work broadens copper alloying choices for CO₂ reduction in aqueous phases.

Aqueous phase reforming (APR) of sugar alcohol molecules derived from biomass, e.g., C_xH_(2x+2)O_x (aq) + xH₂O → xCO₂ (g) + (2x + 1)H₂ (g), creates hydrogen gas sustainably, making it an important component of future bio-refineries; however, problems with the cost, activity, and selectivity of present precious metal based catalysts impede its broader adoption. Ideally, new catalysts would be designed to optimize activity and selectivity; however, a comprehensive understanding of the APR mechanism is lacking. This is complicated by the fact that the primary biomass-derived sugar alcohols are large molecules (meaning that their reaction networks are large) and because of the presence of liquid water. Water influences catalytic phenomena in multiple ways, including altering the thermodynamics of catalytic surface species and participating in catalytic reactions. Understanding the mechanism of APR requires understanding these various effects; however, computational strategies based solely on density functional theory (DFT) are computationally prohibitive for such large and complicated reaction networks. In this work, we investigate the mechanism of APR reactions in the context of glycerol reforming. To calculate the reaction network, we combine DFT calculations, force-field molecular dynamics (MD) simulations, linear scaling relations (LSRs), transition state scaling (TSS) relationships, and data from the literature into a microkinetic model. The microkinetic model is run under vacuum and aqueous phases in order to learn about the roles of water molecules on the mechanism of glycerol APR. We identify four such roles: providing surface hydroxyl groups, which promote oxidation of surface CO formed in glycerol decomposition; promoting C–H scissions; promoting O–H scissions; and inhibiting the thermodynamics of decarbonylation of C3 intermediates.

Water influences catalytic reactions in multiple ways, including energetic and mechanistic effects. While simulations have provided significant insight into the roles that H₂O molecules play in aqueous-phase heterogeneous catalysis, questions still remain as to the extent to which H₂O structures influence catalytic mechanisms. Specifically, influences of the configurational variability in the water structures at the catalyst interface are yet to be understood. Configurational variability is challenging to capture, as it requires multiscale approaches. Herein, we apply a multiscale sampling approach to calculate reaction thermodynamics and kinetics for COH* dehydrogenation to CO* and CH₃OH* dehydrogenation to CH₂OH* on Pt(111) catalysts under liquid H₂O. We explore various pathways for these dehydrogenation reactions that could influence the overall mechanism of methanol decomposition by including participation of H₂O structures both energetically and mechanistically. We find that the liquid H₂O environment significantly influences the mechanism of COH* dehydrogenation to CO* but leaves the mechanism of CH₃OH* dehydrogenation to CH₂OH* largely unaltered.