Rational Catalyst Design Research Articles

Chip−like high−entropy oxide catalysts enhance fast sulfur evolution reaction for long−life lithium−sulfur batteries

Many catalysts have shown excellent activity for the sulfur reduction reaction (SRR), but sluggish electrochemistry kinetics have hindered the development of lithium–sulfur batteries. It has been found that the activity of catalysts for the sulfur evolution reaction (SER) plays a crucial role in determining the overall reaction kinetics. To address this issue, the rational design of catalysts is crucial. Here, we proposed a popular rule to accelerate SER by using chip–like high–entropy perovskite oxide La0.7Sr0.3(Fe0.2Co0.2Ni0.2Zn0.2Mn0.2)O3-δ (LMO–HEO) as advanced electrocatalysts. The strong interaction between the adjacent metal atoms in different metals of LMO–HEO electrocatalysts could lead to a "cocktail effect", which not only greatly improved the catalytic capacity toward sulfur species, but also accelerated the oxidation reaction kinetics of Li2S. As a result, the S/La0.7Sr0.3(Fe0.2Co0.2Ni0.2Zn0.2Mn0.2)O3-δ cathodes delivered excellent cyclic stability with a capacity decay of only 0.025% after 1200 cycles at 2 C. This work has provided a rational design idea for new multifunctional electrocatalysts with high catalytic capacity.

Acidity and stability of Nb(V) active sites doped in SBA-15 and ZrSBA-15: A DFT study

Mesoporous silicas are of great interest in heterogeneous catalysis due to the structural characteristics of their pores and the adjustable catalytic properties that arise from incorporating heteroatoms. The substitution of Zr and Nb into SBA-15 introduces active sites into the material, rendering it a potential catalyst for acid catalysis reactions. However, discussions regarding the acid properties and metal-support interactions in amorphous silicas functionalized with metals are limited in computational chemistry. This study aims to determine the acid strength and charge transfer effects between Zr(IV) and Nb(V) species in mesoporous silica by proposing a representative SBA-15 cluster of type 5–6. Density Functional Theory (DFT) simulations were conducted using the B3LYP/6-31G(d,p)/def2TZVP levels. The model successfully replicated trends from larger clusters, demonstrating that the more grafted onto the silica structure (i.e. have more Si-O-M bonds), the greater the acid strength of the active site. Additionally, it was found that ZrSBA-15 structures are more stable than NbSBA-15 and possess higher acid strength, a trend supported by experimental observations. The results also suggest that Nb(V) species are more effectively stabilized in ZrSBA-15 than SBA-15, likely due to the presence of Zr(IV) centers in ZrSBA-15. This research contribute to a better understanding of how the support affects the stabilization of active phases, paving the way for the rational design of silica-based heterogeneous catalysts.

Theoretical design and synthesis of Co30Ni60/CC for high selective methanol oxidation assisted energy-saving hydrogen production

The integration of methanol oxidation reaction (MOR) with hydrogen evolution reaction (HER) represents an advanced approach to hydrogen production technology. Nonetheless, the rational design and synthesis of bifunctional catalysts for both MOR and HER with exceptional activity, stability and selectivity present formidable challenges. In this work, firstly, density functional theory (DFT) was utilized to design and evaluate material models with high performance for both MOR and HER. Secondly, guided by DFT, Co30Ni60/CC (CC, carbon cloth) composites with a leaf-like nanosheet structure were successfully fabricated via electrodeposition. In the MOR process, Ni acts as the predominant active center, while Co amplifies the electrochemically active surface area (ECSA) and enhances the selectivity of methanol oxidation. Conversely, in the HER process, Co serves as the primary active center, with Ni augmenting the charge transfer rate. The electrochemical results demonstrate that Co30Ni60/CC exhibits exceptional performance in both MOR and HER at a current density (j) of 10 mA cm−2, with peak potentials of 1.323 V and −95 mV, respectively. Additionally, it shows remarkable selectivity for the oxidiation of methanol to high value-added formic acid. Thirdly, following a 100 h chronopotentiometry (CP) test, the required potential demonstrates an increase of 4.9 % (MOR) and 8.1 % (HER), signifying the superior stability of Co30Ni60/CC compared to those reported in the literature. The exceptional performance of Co30Ni60/CC can be primarily attributed to that the leaf-like nanosheets structure not only exposes a plethora of active sites but also facilitates electrolyte diffusion, the monolithic structure prepared by electrodeposition enhances its stability, and the transfer of electrons from Co to Ni regulates its electronic structure, as corroborated by X-ray photoelectron spectroscopy (XPS) and density of states (DOS) analyses. Finally, at the same j, the voltage required by the Co30Ni60/CC||Co30Ni60/CC electrolytic cell, powered by an electrochemical workstation, is 198 mV lower than that required for alkaline water-splitting. Meanwhile, at higher j (100 mA cm−2), the electrolytic cell exhibits sustained and stable operation for 150 h, enabling high-efficiency hydrogen production and the synthesis of high value-added formic acid.

Petroleum Pitch-Derived Porous Carbon Materials as Metal-Free Catalyst for Dry Reforming of Methane.

Porous carbon materials have gained increasing attention in catalysis applications due to their tailorable surface properties, large specific surface area, excellent thermal stability, and low cost. Even though porous carbon materials have been employed for thermal-catalytic dry reforming of methane (DRM), the structure-function relationship, especially the critical factor affecting catalytic performance, is still under debate. Herein, various porous carbon-based samples with disparate pore structures and surface properties are prepared by alkali (K2CO3) etching and the following CO2 activation of low-cost petroleum pitch. Detailed characterization clarifies that the quinone/ketone carbonyl functional groups on the carbon surface are the key active sites for DRM. Density functional theory (DFT) calculations also show that the C=O group have the lowest transition state energy barrier for CH4* cleavage to CH3* (2.15 eV). Furthermore, the cooperative interplay between the specific surface area and quinone/ketone carbonyl is essential to boost the cleavage of C-H and C-O bonds, guaranteeing enhanced DRM catalytic performance. The MC-600-800 catalyst exhibited an initial CH4 conversion of 51% and a reaction rate of 12.6 mmolCH4 gcat.-1 h-1 at 800 °C, CH4:CO2:N2= 1:1:8, and GHSV = 6000 mL gcat.-1 h-1. Our work could pave the way for the rational design of metal-free carbon-based DRM catalysts and shed new light on the high value-added utilization of heavy oils.

Activity of CeO2(111) supported Mnx(x = 1–6) for electrochemical N2 reduction reaction: Insights from density functional theory

It is challenging to realize an efficient nitrogen reduction reaction (NRR) under mild conditions, which suffers from low ammonia yield and low Faraday efficiency due to the extremely stable NN triple bond of N2 as well as competitive hydrogen evolution reaction. In this work, the NRR reactivity of Mnx(x= 1–6) clusters supported on CeO2(111) (Mnx(x = 1–6)/CeO2(111)) was systematically investigated using density functional theory. A volcanic relationship between the limiting potential of NRR on Mnx(x = 1–6)/CeO2(111) and the atom number of Mnx was found. Mn3/CeO2(111) shows the highest activity for NRR with a limiting potential of -0.36, -0.55 and -0.53 V along distal, alternating and enzymatic reaction pathway, respectively. Its high activity is attributed to the triangular geometry and optimal average number of electrons every Mn transferred from Mn3 to CeO2(111), which leads to the strong N2 activation and the stabilization of nitrogen-containing intermediates. Also, Mn3/CeO2(111) exhibits a high NRR selectivity by hindering H adsorption and a high thermal stability at both 298 and 773 K, suggesting its promising potential as effective NRR catalyst. This work provides new insights into the rational design of single cluster catalysts.

Designing water resistant high entropy oxide materials

The ubiquitous presence of moisture usually shows adverse effects on industrial catalysis. Herein, a concept of engineering entropy to design water-resistant oxide catalysts is proposed. The C3H6 oxidation by spinel ACr2O4 (A=Ni, Mg, Cu, Zn, Co) catalysts is selected as a model. Through DFT calculation, the adsorption energy of C3H6, the dissociation energy of molecular H2O on the oxide surface, and the formation energy of oxygen vacancy all suggest better performance induced by higher configurational entropy. Indeed, (Ni0.2Mg0.2Cu0.2Zn0.2Co0.2)Cr2O4 experimentally show excellent water resistance (>100 h) in C3H6 oxidation, while in sharp contrast binary oxides (e.g., NiCr2O4, CoCr2O4) are deactivated in 20 h. H2O-TPD, in-situ Raman, and in-situ FTIR all confirm the low H2O adsorption energy and strong hydrothermal stability of high entropy oxide, which is attributed to their lower Gibbs free energy. This work may inspire the rational design of water-resistant catalysts.

Study on the synthesis of CoFe/CoFe2O4@NCNTs derived from ZnFeCo-ZIF with abundant heterostructures and oxygen vacancies as bifunctional catalyst for ORR/OER in zinc-air batteries

The rational design of bifunctional catalysts for oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) in alkaline electrolyte is of great significance for zinc-air batteries (ZABs). In this study, different types of Fe/Co compounds and nitrogen-doped carbon-based composite catalysts from trimetallic zeolitic-imidazole-framework-derived (ZnFeCo-ZIF) were synthesized by adjusting the ratio of Zn/Fe/Co. Among them, the synthesized CoFe/CoFe2O4-N-doped carbon nanotubes (CoFe/CoFe2O4@NCNTs) have abundant Fe-Nx and Co-Nx activity sites, heterostructures and oxygen vacancies. The experimental results reveal that the electrons of CoFe are transferred to CoFe2O4 at the interface of CoFe/CoFe2O4, which not only enhances the electron transfer ability, but also induces oxygen vacancies to improve the adsorption/desorption capacity of O2 and intermediates. Meanwhile, metal atoms are uniformly dispersed in the N-doped carbon nanotubes to form metal–N sites with high catalytic activity. Therefore, the CoFe/CoFe2O4@NCNTs exhibit excellent electrocatalytic performance, possessing a half-wave potential (E1/2) of 0.878 V and a prominent limiting-current densities (JL) of 6.281 mA cm−2 for ORR, and a low overpotential of 344 mV at 10 mA cm−2 for OER. In particular, the CoFe/CoFe2O4@NCNTs-equiped ZAB possesses a higher open-circuit voltage (1.50 V), a greater maximum power density (193.42 mW cm−2) and a longer cycling performance (160 h). The density functional theory (DFT) calculations show that the CoFe/CoFe2O4 heterostructure can induce the rapid transfer of electrons at the CoFe/CoFe2O4 interface, which promotes the change of the surface electronic structure of the catalyst, and thus helps to enhance the ability of the catalyst to transfer electrons.

Visualization of Electrooxidation on Palladium Single Crystal Surfaces via In Situ Raman Spectroscopy.

The electrooxidation of catalyst surfaces is across various electrocatalytic reactions, directly impacting their activity, stability and selectivity. Precisely characterizing the electrooxidation on well-defined surfaces is essential to understanding electrocatalytic reactions comprehensively. Herein, we employed in situ Raman spectroscopy to monitor the electrooxidation process of palladium single crystal. Our findings reveal that the Pd surface's initial electrooxidation process involves forming *OH intermediate and ClO4 - ions facilitate the deprotonation process, leading to the formation of PdOx. Subsequently, under deep electrooxidation potential range, the oxygen atoms within PdOx contribute to creating surface-bound peroxide species, ultimately resulting in oxygen generation. The adsorption strength of *OH and the coverage of ClO4 - can be adjusted by the controllable electronic effect, resulting in different oxidation rates. This study offers valuable insights into elucidating the electrooxidation mechanisms underlying a range of electrocatalytic reactions, thereby contributing to the rational design of catalysts.

Visualization of Electrooxidation on Palladium Single Crystal Surfaces via In Situ Raman Spectroscopy

AbstractThe electrooxidation of catalyst surfaces is across various electrocatalytic reactions, directly impacting their activity, stability and selectivity. Precisely characterizing the electrooxidation on well‐defined surfaces is essential to understanding electrocatalytic reactions comprehensively. Herein, we employed in situ Raman spectroscopy to monitor the electrooxidation process of palladium single crystal. Our findings reveal that the Pd surface's initial electrooxidation process involves forming *OH intermediate and ClO4− ions facilitate the deprotonation process, leading to the formation of PdOx. Subsequently, under deep electrooxidation potential range, the oxygen atoms within PdOx contribute to creating surface‐bound peroxide species, ultimately resulting in oxygen generation. The adsorption strength of *OH and the coverage of ClO4− can be adjusted by the controllable electronic effect, resulting in different oxidation rates. This study offers valuable insights into elucidating the electrooxidation mechanisms underlying a range of electrocatalytic reactions, thereby contributing to the rational design of catalysts.

Boosting Electroreduction of Nitrate and CO2 to Urea on a Tandem Fe1/MoS2 Catalyst.

Urea electrosynthesis by coelectrolysis of NO3- and CO2 (UENC) holds enormous promise for sustainable urea production, while the efficient UENC process relies on the rational design of high-performance catalysts to facilitate the electrocatalytic C-N coupling efficiency and the hydrogenation reaction process. Herein, Fe single atoms supported on MoS2 (Fe1/MoS2) are developed as a highly effective and robust catalyst for UENC. Theoretical calculations and operando spectroscopic measurements reveal a tandem catalysis mechanism of the Fe1-S3 motif and MoS2-edge to jointly promote the UENC process, where the Fe1-S3 motif drives the early C-N coupling and subsequent *CO2NO2-to-*CO2NH2 step. The generated *CO2NH2 is then migrated from the Fe1-S3 motif to the nearby MoS2-edge, which facilitates the *CO2NH2 → *COOHNH2 step for urea formation. Noticeably, Fe1/MoS2 assembled in a flow cell reaches a maximum urea Faraday efficiency of 54.98% with a corresponding urea yield rate of 18.98 mmol h-1 g-1, performing at the top level among all of the UENC catalysts reported to date.

Transition metal atoms embedded into B/N co-doped graphene as electrocatalysts toward nitrogen reduction reaction: Search for the optimal combination

The catalytic performance of a series of single transition metal (TM = 3d, 4d, and 5d series) atoms anchored on B/N co-doped graphene (BxNy@Gra) toward electrocatalytic nitrogen reduction reaction (eNRR) was systematically investigated by first-principles calculations. Among 180 possible materials, four catalysts (Tc-B1N3@Gra, Os-B2N2α@Gra, Re-B2N2γ@Gra, Nb-B3N1@Gra) feature the highest activity with UL no higher than 0.31 V. Interestingly, a volcano curve between UL and ΔEads(*NNH) can be established, so ΔEads(*NNH) can be applied as a descriptor to unveil the structure-activity relationship and characterize the activity of catalysts. The properties, thermal stability, and selectivity for the four catalysts were analyzed. Os-B2N2α@Gra is identified as a promising catalyst in this work for catalyzing N2 electroreduction to NH3 owing to its potent catalytic activity (UL = −0.28 V), high stability and distinct selectivity. This work can give some meaningful guidance for rapid screening and the rational design of efficient single-atom catalysts for electrocatalytic ammonia synthesis and other related electrochemical reaction. We expect that the present study will inspire and promote the efforts from both experimental and theoretical in this direction.

Crystal-dependent doping effects over MnO2 for Fenton-like catalysis optimization

Heteroatom doping is one of the most important strategies to improve the Fenton-like activity of heterogenous catalysts by optimizing the coordination environment and electronic structure of active sites. However, the doping effect on the crystal structure that governs the atom orientation and chemical stability of catalysts remains largely elusive. Here, we report the rational design and synthesis of a series of fluorine-doped MnO2 catalysts with different crystal phases (denoted as F-α-, F-β-, F-γ-, and F-δ-MnO2), aiming to reveal the crystal-dependent disparity of doping effects in PMS activation. Results demonstrate that fluorine doping exhibits selectivity towards specific crystal structures of MnO2 catalyst. The γ-MnO2 with a lowest Mn average oxidation state (AOS) significantly enhances the adsorption and activation of PMS upon fluorine doping, outperforming other MnO2 counterparts (i.e., α, β, and δ-type). Interestingly, we identify a strong linear correlation (R2 = 0.99) between the degradation rate constant variation (Δk) and ΔAOS divergence of MnO2 catalysts before and after fluorine doping, revealing a novel structure–activity relationship for Fenton-like catalysis optimization. In addition, a nonradical pathway with synergism of 1O2 and active surface-complex contributes greatly to pollutant removal in the developed F-γ-MnO2/PMS system, thereby demonstrating outstanding degradation performance towards electron-rich organics. This work provides fundamental insights into the crystal structure–activity relationship in the disparity of doping effect, which may inspire the rational design of efficient Fenton-like catalysts for wastewater treatment.

Polymorph interface strategy presents avenues for kinetics-enhanced and dendrite-free lithium sulfur batteries

Shuttle effect and slow kinetic property are the challenges for the practical application of lithium-sulfur (Li-S) batteries. As an effective strategy, the polymorph effect is applied to rationally design multifunctional catalysts. Herein, the unique polymorph interface was constructed by different CoSe2 crystalline phases, and the systematic investigation on the sulfur cathodes and lithium anode is reported. Carbon nanofiber (CNF) derived from bacterial cellulose (BC) is used as a scaffold for disperse CoSe2 catalysts to construct electrically conductive highways. According to the experimental and calculation results, orthorhombic CoSe2 exhibits superior adsorption capacity and catalytic activity towards LiPSs, while cubic CoSe2 shows better electronic conductivity. Mixed phase CoSe2 not only balances the advantages of both, but also showcases impressive performance due to its unique polymorph interface structure. Besides, uniform lithium deposition can be also achieved. Consequently, the modified separators endow Li-S batteries with a high reversible discharge capacity (700 cycles at 1 C with only 0.063 % capacity decay per cycle) and excellent rate performance (702 mAh g−1 is maintained at 5 C). The pouch cell with separator modifications on both sides was assembled and exhibits a high discharge capacity. This work provides a polymorph interface strategy for the rational design of catalysts.

Rational Linker Design for Enhanced Performance of MOF-Derived Catalysts in Electrochemical Urea Synthesis.

2D metal-organic frameworks (2D MOFs) offer promising electrocatalytic potential for urea synthesis, yet the underlying reaction mechanisms and structure-activity relationships remain unclear. Using Cu-BDC as a model, density functional theory (DFT) calculations to elucidate these aspects are conducted. The results reveal a novel coupling mechanism involving *NO─CO and *NO─*ONCO, emphasizing the impact of linker modifications on Cu spin states and charge distribution. Notably, Cu-BDC-NH2 and Cu─BDC─OH emerge as promising catalysts. Additionally, structure-activity relationships through descriptors like d-band center, IE ratio, and L(Cu─O), providing insights for rational catalyst design is established. These findings pave the way for optimized catalysts and sustainable urea production, opening avenues for future research and technological advancements.

Light-Driven Reverse Water Gas Shift Reaction with 1000-H Stability on High-Entropy Alloy Catalysts.

Highly stable and active catalysts are of significant importance and a longstanding challenge for a number of industrial chemical transformations. Here, motivated by the principle of the high entropy-stabilized structure, high-entropy alloy-loaded porous TiO2 as an efficient and sintering-resistant catalyst for the light-driven reverse water gas‒shift reaction without external heating is synthesized. The optimized CoNiCuPdRu/TiO2 catalyst exhibits a long-term stability of 1000h (1.23molgmetal -1h-1 CO production rate, >99% high selectivity). In situ characterizations confirm that the slow diffusion effect of high-entropy alloys endows the catalyst with excellent structural stability. The CO adsorption measurements and theoretical calculations consolidate that the hydrogen surface coverage weakens CO adsorption on the catalyst surface. Two major problems of catalyst deactivation - sintering and poisoning, are handled in one case, which synergistically enable unparalleled stability. This work provides new guidance for the rational design of ultradurable harsh-condition operation catalysts for industrial catalysis.

Controlled formation of CoOOH/Co(III)-MOF active phase for boosting electrocatalytic alkaline water oxidation

Surface reconstituted metal-organic frameworks (MOFs) offer appealing properties for electrocatalysis due to their unique structural and compositional advantages. In this work, a controlled potential-induced reconstruction of a two-dimensional cobalt metal-organic framework for boosting oxygen evolution reaction in alkaline media is reported. The current MOF is shown to undergo a partial structural transformation that generates a heterogeneous system, where the original MOF coexists with an oxyhydroxide phase. In fact, the potential-induced stabilization of Co(III) metal centers in the MOF is crucial for delaying its full degradation in alkaline media. This partial retention of the Co(III)MOF phase in the so-derived heterogeneous catalyst has been demonstrated to be decisive for boosting the alkaline electrocatalytic oxygen evolution reaction (OER), displaying superior OER activity in terms of both thermodynamic and kinetic merits compared to the benchmark IrO2 and RuO2 electrocatalysts and the prototypical cobalt (oxy)hydroxides, with a Tafel slope of 52 mV dec−1 and a turnover frequency (TOF) of 6.8 s−1 at 450 mV. Remarkably, the generated final product is stable, exhibiting high robustness and long durability for long-term OER electrolysis. This work provides new insight into the impact of the reconstruction of a MOF for alkaline OER under typical electrochemical conditions, which ultimately benefits the rational design of MOF-based catalysts with high electrocatalytic activity for oxidation reactions.

Diverse effects of ferromagnetic-paramagnetic phase transition on the activity and selectivity of ferromagnetic catalysts

Tuning the catalyst’s activity and selectivity is usually achieved by modifying the electronic structure through strategies such as alloying, doping, strain, and ligand modification, but inevitably accompanied by geometric structure changes of catalysts. It is challenging to modify a catalyst’s electronic structure without changing its geometric structure. Recent studies found that the second-order ferromagnetic to paramagnetic (FM-PM) phase transition could promote catalytic performance without altering the geometric structures of active sites, which was also known as the magneto-catalytic effect (MCE). However, the understanding of the MCE is still incomplete. Herein, we conducted systematic density functional theory (DFT) calculations to clarify the complex reaction mechanisms for conversions of nitrogen-containing small molecules on both FM and PM Ni (111) surfaces. Our microkinetic modeling (MKM) results demonstrate that FM-PM phase transition promotes the N2O decomposition activity of FM Ni catalyst but decreases its activity for NO decomposition while showing a negligible influence on the activity of ammonia decomposition. These results indicate the promotion, inhibition, and disappearance mechanisms of MCE on the catalytic activity, which further changes the selectivity of different products. We anticipate the MCE will work as an effective strategy for fine-tuning the activity and selectivity of ferromagnetic catalysts in heterogeneous catalysis, providing an extra basis for rational catalyst design.

Unraveling Lewis acid-base sites in defected MOFs for catalyzing dicyclopentadiene hydrogenation via a DFT study and descriptor exploration

The 12-connected UiO-66 MOFs with great defect regulation ability have attracted significant attention due to the easily tunable electronic structure and surface electrostatic potential distribution of metal nodes. In this density functional theory (DFT) study, we systematically explored the effect of bi-active site types as the frustrated Lewis pair (FLP) and classical Lewis pair (LP) as well as metal elements of secondary building units (SBUs) on the catalytic hydrogenation of dicyclopentadiene (DCPD) to tetrahydrodicyclopentadiene (THDCPD). These design strategies effectively modulate the frontier molecular orbital energy level that determines the binding strength between MOFs and adsorbed species *Hδ+-Hδ- and charges transfer before and after H2 chemisorption. We also found that the heterolytic H2 adsorption energy and charges transfer linearly correlate with the energy barrier. In order to unravel the clear-cut designing strategies and further simplify computational complexity, we firstly proposed the ADCH charges difference between the Lewis acid and the Lewis base centers (ΔQM-O) as an intrinsic descriptor for catalytic activity of DCPD into THDCPD, which can effectively describe the reactivity and electrostatic effects of oppositely charged bi-active sites in the system. Furthermore, the defective UiO-66(Ce) MOF with moderate ΔQM-O effectively balance the contradiction between the barriers of two primitive reaction: the heterolytically H2 dissociation to *Hδ+-*Hδ- and the desorption of the active hydrogen species to hydrogenate 8,9-dihydrodicyclopentadiene (8,9-DHDCPD), resulting in the optimal catalytic performance. This work provides a deep understanding of the catalytic mechanism of MOFs with multiple active sites and might open up avenues for the rational design of novel hydrogenation catalysts.

Hydrogen adsorption on fcc metal surfaces towards the rational design of electrode materials

The successful large-scale implementation of hydrogen as an energy vector requires high performance electrodes and catalysts made of abundant materials. Rational materials design strategies are the most efficient means of reaching this goal. Here we present a study on the adsorption of H-atoms onto fcc transition metal surfaces and propose descriptors for the rational design of electrodes and catalysts by means of correlations between fundamental properties of the materials and among other properties, their experimentally measured performance as hydrogen evolution electrodes (HEE). A large set of quantum mechanical modelling data at the DFT level was produced, covering the adsorption of H-atoms onto the most stable surfaces (100), (110) and (111) of: Ag, Au, Co, Cu, Ir, Ni, Pd, Pt and Rh. For each material and surface, a coverage dependent set of minimum energy structures was produced and chemical potentials for adsorption of H-atoms were obtained. Averaging procedures are here proposed to approach modelling to the experiments. Several correlations between the computed data and experimentally measured quantities are done to validate our methodology: surface plane dependent adsorption energies, chemical potentials and experimentally determined surface energies and work functions. We search for descriptors of catalytic activity by testing correlations between the DFT data obtained from our averaging procedures and experimental data on HEE performance. Our methodology allows us to obtain linear correlations between the adsorption energy of H-atoms and the exchange current density (i0) in a HEE, avoiding the volcano-like plots. We show that the chemical potential has limitations as a descriptor of i0 because it reaches an early plateau in terms of i0. Simple quantities obtained from database data such as the first stage electronegativity (χ) as devised by Mulliken has a strong linear correlation i0. With a quantity we denominate modified second-stage electronegativity (χ2m) we can reproduce the typical volcano plot in a correlation with i0. A theoretical and conceptual framework is presented. It shows that both χ and χ2m, that depend on the first ionization potential, second ionization potential and electron affinity of the elements can be used as descriptors in rational design of electrodes or of catalysts for hydrogen systems.

Post-Synthetic Modification of a 1D Mixed-Linker Zn(II) Coordination Polymer for Acid-Catalyzed Alcoholysis of Epoxides.

Rational design of heterogeneous acid catalysts possessing uniform dispersion of active sites plays a significant role in the catalytic performance. In the present work, a coordination polymer, [Zn(4,4'-bpy)(μ-Hbtc)(H2O)] ⋅ 2H2O (Zn-CP), was solvothermally synthesized using 4,4'-bpy (=4,4'-bipyridine) and H3btc (=1,3,5-benzenetricarboxylic acid) mixed linkers. Single crystal X-ray analysis of the polymer displayed that Zn-CP chains were decorated with 4,4'-bpy having unidentate coordination fashion. Then, the free N atom of the linker in Zn-CP was functionalized by -SO3H groups to afford Zn-CP-SO3H with enhanced acidity. The structures were characterized by FT-IR, thermogravimetric analysis, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature programmed desorption of NH3 (NH3-TPD), and field emission scanning electron microscopy (FE-SEM) analyses. The coordination polymer was employed as a heterogeneous catalyst for the alcoholysis of epoxides under room conditions. Zn-CP-SO3H exhibited excellent catalytic activity and regioselectivity in the methanolysis of styrene oxide within short reaction time.