Open Access

Show Abstract ▼

Abstract: The transition to net-zero emissions hinges on circular economy strategies that valorize waste and enhance resource efficiency. Among X-to-liquid (XTL) technologies, the Fischer-Tropsch (FT) process stands out for converting biomass, waste, and CO2 into hydrocarbons and chemicals, especially when powered by renewable hydrogen. Cobalt-based catalysts are preferred in FT synthesis due to their efficiency and CO2 tolerance, yet their catalytic performance is closely tied to their polymorphic structures─face-centered cubic (FCC), hexagonal close-packed (HCP), and stacking-faulted intergrowths thereof. HCP cobalt has been shown to exhibit high activity and selectivity for higher hydrocarbons and oxygenates, particularly when transformed into cobalt carbide (Co2C), which forms more readily at low H2/CO ratios. This study presents a quantitative analysis of cobalt polymorphs and stacking faults in Mn-promoted Co/TiO2 FT catalysts from in situ powder X-ray diffraction (XRD) data and X-ray Diffraction Computed Tomography (XRD-CT) data from spent catalysts in order to obtain a more complete correlation of structural features with catalytic performance. By modeling stacking fault probabilities using supercell simulations, the proportion of faulted FCC and HCP domains was determined across varying Mn loadings (0–5%). Increased Mn loading was found to decrease stacking faults in the FCC phase while increasing them in HCP, promoting the formation of HCP domains and ultimately Co2C under reaction conditions. Notably, the 3% Mn-loaded sample showed a marked rise in HCP content and Co2C formation, correlating with the highest observed alcohol and olefin selectivity. These findings highlight a critical structure–function relationship: Mn facilitates a transformation from FCC to HCP and then to Co2C, this final transition driven by similar stacking sequences and metal–support interactions. The findings show that Mn promotion not only stabilizes smaller Co particles and enhances its dispersion, but also modulates the distribution of Co polymorphs and stacking faults, leading to altered catalytic behavior. This highlights the importance of stacking fault characterization for optimizing FT catalyst design and performance, and suggests pathways to more efficient and selective carbon-neutral fuel production through engineered polymorphic and interfacial structures.

Show Abstract ▼

Abstract: Understanding factors controlling product selectivity in CO2 hydrogenation remains a central research theme for catalytic CO2 utilization. Here, we report a composition-dependent selectivity anomaly in the In–Pd intermetallic series (viz., InPd2, InPd, In3Pd2), where In3Pd2 exhibits 100% CO selectivity via the reverse water–gas shift (RWGS) pathway, in sharp contrast to the high methanol selectivity achieved on other In-rich or Pd-rich metals or intermetallic compounds. Comprehensive characterization reveals that this anomaly arises from Pd enrichment on the surface of In3Pd2 IMC nanoparticles. The enriched Pd sites, modulated by In-to-Pd electron transfer, favor CO formation. In addition, the In-rich sites neighboring the Pd-rich islands facilitate rapid CO desorption. The resulting nanostructure on the surface of In3Pd2 IMCs renders an electronic interaction between In and Pd to promote CO formation and suppress C–H bond formation. This rationale is supported by both density functional theory (DFT) calculations and experimental evidence. These findings demonstrate that compositional control in intermetallic catalysts enables switchable CO2 hydrogenation selectivity and offers a rational approach to designing catalysts with tailored product distributions.

Show Abstract ▼

Abstract: This study addresses the longstanding challenge of optimizing platinum catalysts for industrial ammonia oxidation─a reaction central to nitrogen-based chemical synthesis─by uncovering the dynamic link between surface structure and selectivity under realistic conditions. Using a combination of operando surface X-ray diffraction, crystal truncation rod analysis, and near-ambient pressure X-ray photoelectron spectroscopy, we exposed Pt(100) to reaction conditions and observed the formation of an epitaxial Pt3O4(001) phase during initial oxidation, followed by distinct (10 × 10) and hexagonal surface reconstructions as active phases, dictated by the pO2/pNH3 pressure ratio. Critically, surface roughness emerged as a key descriptor: smooth surfaces under low oxygen conditions drive N2 selectivity, while roughened surfaces at high oxygen favored NO production, revealing how structural evolution governs catalytic behavior. These insights not only advance fundamental understanding of structure–function relationships in platinum catalysis but also provide a framework for designing industrially robust catalysts through precise surface engineering.

Open Access

Show Abstract ▼

Abstract: The distribution of elements within alloy nanoparticles is a critical parameter for their electrocatalytic performance. Here, we use the case of a Pt3Ni alloy to show that this elemental distribution can dynamically respond to the applied potential, leading to strongly potential-dependent catalytic properties. Starting from the Pt3Ni core and Pt shell structure that forms in acid electrolyte due to Ni leaching, our electrochemical X-ray photoelectron spectroscopy measurements show that the Ni atoms can be reversibly moved between the core of the particles and the near-surface region using the applied potential. Through potential jump measurements, we show that this Ni migration modulates the hydrogen evolution reaction activity of the particles by over 30%. These observations highlight the potential of incorporating in situ restructuring of alloys as the final step in electrocatalyst design.

Open Access

Show Abstract ▼

Abstract: Reducing CO2 to CO via the reverse water–gas shift (RWGS) reaction is a promising strategy for carbon capture and utilization (CCU). In this study, tailored magnetic catalysts were designed through the pyrolysis of a Co-based MOF to form well-defined nanoparticles. As a result, carbon-encapsulated cobalt nanoparticles (Co@C) and palladium-doped cobalt nanoparticles (CoPd/Co@C) were synthesized and thoroughly characterized using a variety of techniques, including in situ X-ray absorption and diffraction experiments. These carbon-based catalysts were simultaneously used as heating agents and catalysts for the magnetically induced RWGS reaction, exhibiting remarkable activity and selectivity for syngas production. CO2 conversions of 61.1% and 71.1% were obtained for Co@C and CoPd/Co@C (63 mT, 2 kW, 320 kHz), respectively. Using magnetic induction heating (MIH), these catalysts operate at lower local temperatures and with greater energy efficiency than conventional thermal heating, while achieving superior CO production efficiency. Notably, CoPd/Co@C achieved highly satisfactory CO production efficiency (478.5 mLCO/kW·h), demonstrating a significant improvement compared to the analogous process utilizing magnetically induced heating. Furthermore, CoPd/Co@C exhibited unwavering stability, maintaining its performance for more than 200 h without significant degradation or need for reactivation. This study highlights the potential of MIH for industrial applications in CO2 reduction, offering a more renewable and economically viable alternative to traditional methods.