Powered by DFT: Screening methods that accelerate materials development for hydrogen in metals applications

Mechanocatalytic Hydrogenolysis of the Lignin Model Dimer Benzyl Phenyl Ether over Supported Palladium Catalysts

This work demonstrates the mechanocatalytic hydrogenolysis of the ether bond in the lignin model compound benzyl phenyl ether (BPE) and hardwood lignin isolated by hydrolysis with supercritical water. Pd catalysts with 4 wt % loading on Al2O3 and SiO2 supports achieve 100% conversion of BPE with a toluene production rate of (2.6-2.9) × 10-5 mol·min-1. The formation of palladium hydrides under H2 gas flow contributes to an increase in the turnover frequency by a factor of up to 300 compared to Ni on silica-alumina. While a near-quantitative toluene yield is obtained, some of the phenolic products remain adsorbed on the catalyst.

Nanoporous Ni3P Evolutionarily Structured onto a Ni Foam for Highly Selective Hydrogenation of Dimethyl Oxalate to Methyl Glycolate

Methyl glycolate (MG) is a versatile platform molecule to produce numerous important chemicals and materials, especially new-generation biocompatible and biodegradable poly(glycolic acid). In principle, it can be massively produced from syngas (CO + H₂) via gas-phase hydrogenation of CO-derived dimethyl oxalate (DMO), but the groundbreaking catalyst represents a grand challenge. Here, we report the discovery of a Ni-foam-structured nanoporous Ni₃P catalyst, evolutionarily transformed from a Ni₂P/Ni-foam engineered from nano- to macro-scale, being capable of nearly fully converting DMO into MG at >95% selectivity and stable for at least 1000 h without any sign of deactivation. As revealed by kinetic experiments and theoretical calculations, in comparison with Ni₂P, Ni₃P achieves a higher surface electron density that is favorable for MG adsorption in a molecular manner rather than in a dissociative manner and has much higher activation energy for MG hydrogenation to ethylene glycol (EG), thereby markedly suppressing its overhydrogenation to EG.

Nano-Intermetallic InNi3C0.5 Compound Discovered as a Superior Catalyst for CO2 Reutilization

CO₂ circular economy is urgently calling for the effective large-scale CO₂ reutilization technologies. The reverse water-gas shift (RWGS) reaction is the most techno-economically viable candidate for dealing with massive-volume CO₂ via downstream mature Fischer-Tropsch and methanol syntheses, but the desired groundbreaking catalyst represents a grand challenge. Here, we report the discovery of a nano-intermetallic InNi₃C_0.5 catalyst, for example, being particularly active, selective, and stable for the RWGS reaction. The InNi₃C_0.5(111) surface is dominantly exposed and gifted with dual active sites (3Ni-In and 3Ni-C), which in synergy efficiently dissociate CO₂ into CO* (on 3Ni-C) and O* (on 3Ni-In). O* can facilely react with 3Ni-C-offered H* to form H₂O. Interestingly, CO* is mainly desorbed at and above 400°C, whereas alternatively hydrogenated to CH₃OH highly selectively below 300°C. Moreover, this nano-intermetallic can also fully hydrogenate CO-derived dimethyl oxalate to ethylene glycol (commodity chemical) with high selectivity (above 96%) and favorable stability.

Grain Boundary Segregation in Pd-Cu-Ag Alloys for High Permeability Hydrogen Separation Membranes

Dense metal membranes that are based on palladium (Pd) are promising for hydrogen separation and production due to their high selectivity and permeability. Optimization of alloy composition has normally focused on bulk properties, but there is growing evidence that grain boundaries (GBs) play a crucial role in the overall performance of membranes. The present study provides parameters and analyses of GBs in the ternary Pd-Ag-Cu system, based on first-principles electronic structure calculations. The segregation tendency of Cu, Ag, and vacancies towards 12 different coherent ∑ GBs in Pd was quantified using three different procedures for relaxation of supercell lattice constants, representing the outer bounds of infinitely elastic and stiff lattice around the GBs. This demonstrated a clear linear correlation between the excess volume and the GB energy when volume relaxation was allowed for. The point defects were attracted by most of the GBs that were investigated. Realistic atomic-scale models of binary Pd-Cu and ternary Pd-Cu-Ag alloys were created for the ∑5(210) boundary, in which the strong GB segregation tendency was affirmed. This is a starting point for more targeted engineering of alloys and grain structure in dense metal membranes and related systems.