The accurate and reliable microkinetic modeling of electrochemical CO 2 reduction requires a synergistic combination of experimental and computational approaches, alongside the use of operando spectroscopies as complementary techniques.
Abstract The advancement of ethane (C 2 H 6 )‐selective materials offers the potential for developing energy‐efficient adsorptive separation processes to obtain high‐purity ethylene (C 2 H 4 ) directly. However, these materials still suffer challenges of low selectivity, high cost, and poor stability. Herein, we presented a commercially scalable and stable MFI topology zeolite material (TS‐1) with excellent ideal adsorption solution theory (IAST) selectivity (2.07) and separation potential (0.64 mmol g −1 ). Polymer‐grade ethylene (99.9%) could be afforded with the productivity of 11.5 L kg −1 through the adsorption column packed with TS‐1 material. Additionally, pure silica zeolite with DOH topology with excellent IAST selectivity (2.93) and separation potential (1.64 mmol g −1 ) was discovered by high‐throughput screening via the combination of experiments and simulations. These findings highlight that pure silica zeolites hold promise as C 2 H 6 ‐selective adsorbents for large‐scale implementation for one‐step C 2 H 4 purification.
Aqueous formic acid dehydrogenation (FAD) is a crucial process for hydrogen production, as hydrogen is a clean energy carrier. During this process, formic acid converts into hydrogen and carbon dioxide over a catalyst. Pd-based catalysts have exhibited significant potential in FAD due to their high activity and selectivity. In this study, we investigated aqueous thermal FAD in a mixture of formic acid and sodium formate using electrochemical open-circuit potential (OCP) measurement by loading the catalysts onto a conductive substrate as a working electrode. By varying the reaction conditions such as the concentration of reactants and modifying Pd with Ag, different FAD rates were obtained. Consequently, we revealed the correlation between the catalyst OCP and FAD rate; superior FAD rates reflected a more negative catalyst OCP. Furthermore, deactivation was observed across all catalysts during FAD, with a concurrent increase in catalyst OCP. Interestingly, we found that the logarithm of the FAD rate showed a linear correlation with the OCP of the catalyst during the decay phase, which we quantitatively explained based on the reaction mechanism. This study presents a new discovery that bridges thermal and electrocatalysis.
Physisorption-driven removal of acetylene (C2H2) from ethylene (C2H4) is a promising pathway to produce polymer-grade C2H4. However, advances have been constrained by the compromise needed between selectivity and adsorption capacity. Herein, physisorption-mediated separation of trace C2H2 from C2H4 was carefully examined over pillared metal–organic frameworks (MOFs) through a combination of experiments and theoretical calculations, disclosing that concurrent enhancement of C2H2 uptake capacity and selectivity under low C2H2 pressure conditions was observed due to pore-environment engineering of MOFs. Compared to its counterparts including −H and −NH2, the −CH3-functionalized MOF, named ZU-901, could achieve the highest separation performance, delivering a C2H2 uptake capacity of 0.57 mmol·g–1 at 0.01 bar and an ideal adsorbed solution theory selectivity of ca. 83 for a mixture of C2H2 and C2H4 with a volumetric ratio of 1:99 (1% C2H2/99% C2H4 (V/V)) at 298 K. Their efficiency for C2H2/C2H4 separation, especially in the low-pressure range, was demonstrated by dynamical breakthrough experiments, where the breakthrough time reached 220 min·g–1 under a 1% C2H2/99% C2H4 (V/V) flow rate of 2 mL min–1. Theoretical calculations pointed out that ZU-901 with ligand functionalization has the optimized pore environment and aperture size, boosting the selectively accommodated C2H2 via the synergetic effect of O···H(HC≡) and H(H2pzdc, −CH3)···C(C≡) interactions between C2H2 molecules and frameworks. This work presents an example of pore-environment optimization to break the selectivity-capacity trade-off toward the purification of C2H4 by the removal of C2H2.
Iron porphyrin-based molecular catalysts can electrocatalyze CO2 reduction to CO at nearly 100% selectivity in water. Nevertheless, the associated active sites and reaction mechanisms remain debatable, impeding the establishment of design guidelines for effective catalysts. This study reports coupling in operando experiments and theoretical calculations for immobilized 5,10,15,20-tetrakis(pentafluorophenyl) porphyrin Fe(III) chloride (FeF20TPP) for electrocatalytic CO2 reduction in an aqueous phase. In operando UV–vis and X-ray absorption near-edge structure spectra indicated the persisting presence of Fe(II) species during the cathodic reaction, acting as catalytic sites that accommodate CO as Fe(II)–CO adducts. Consistently, the density functional calculations pointed out that the ligand-reduced state with oxidized Fe, namely, [Fe(II)F20(TPP•)]−, prevails in the catalytic cycle prior to the rate-controlling step. This work provides the conclusive representation related to the working states of Fe-based molecular catalysts under reaction conditions.
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