Hydrogen as the cleanest energy carrier is a promising alternative renewable resource to fossil fuels. There is an ever-increasing interest in exploring efficient and cost-effective approaches of hydrogen production. Recent experiments have shown that single platinum atom immobilized on the metal vacancies of MXenes allows a high-efficient hydrogen evolution reaction (HER). Here using ab initio calculations, we design a series of substitutional Pt-doped Tin+1CnTx (Tin+1CnTx-PtSA) with different thicknesses and terminations (n = 1, 2 and 3, Tx = O, F and OH), and investigate the quantum-confinement effect on the HER catalytic performance. Surprisingly, we reveal a strong thickness effect of the MXene layer on the HER performance. Amongst the various surface-terminated derivatives, Ti2CF2-PtSA and Ti2CH2O2-PtSA are found to be the best HER catalysts with the change of Gibbs free energy ΔG*H ~ 0 eV, complying with the thermoneutral condition. The ab initio molecular dynamics simulations reveal that Ti2CF2-PtSA and Ti2CH2O2-PtSA possess a good thermodynamic stability. The present work shows that the HER catalytic activity of the MXene is not solely governed by the local environment of the surface such as Pt single atom. We point out the critical role of thickness control and surface decoration of substrate in achieving a high-performance HER catalytical activity.
MXenes are a class of 2D/layered materials which are highly conductive, hydrophilic, have a large electrochemical surface area and are easily processible into electrodes for energy applications. Since the discovery of MXenes over ten years ago, these materials have been mainly used in the preparation of electrodes for batteries and supercapacitors. However, due to their aforementioned properties, MXenes could potentially be utilised as a component in the catalyst layer for the Oxygen Evolution Reaction (OER). This opinion piece will discuss some of the recent literature in the area of hybrid c…
MXenes with versatile chemistry and superior electrical conductivity are prevalent candidate materials for energy storage and catalysts. Inspired by recent experiments of hybridizing MXenes with carbon materials, here we theoretically design a series of heterostructures of N-doped graphene supported by MXene monolayers as bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). Our first-principles calculations show that the graphitic sheet on V2C and Mo2C MXenes are highly active with an ORR overpotential down to 0.36 V and reaction free ene…
The functioning of 2D d2, d3, and d4 transition metal carbides as CO2 conversion catalysts has been proved by well resolved density functional theory (DFT) and DFT+U theoretical calculations. Whilst MXenes from the d2 series (M = Ti, Zr, and Hf) have demonstrated active behaviors for the capture of CO2, the V3C2, Nb3C2, Cr3C2, and Mo3C2 materials exhibit the most promising results for their application in the selective CO2 conversion into CH4, with limiting reaction energies of 1.55, 1.75, 0.69, and 1.24 eV, respectively, at DFT+U computational level plus explicit DFT-D3 dispersion corrections…
Combining first-principles modeling and symbolic regression for designing efficient single-atom catalysts in Oxygen Evolution Reaction on Mo$_2$CO$_2$ MXenes
该研究结合第一性原理建模、ESSI 分析与符号回归，筛选 Mo$_2$CO$_2$ MXenes 上的 OER 单原子催化剂，发现 Cu 过电位最低，并提取关键描述符与过电位公式。
We adapt the computational hydrogen electrode approach to explicitly account for photo-generated charges and use it to computationally screen for viable catalyst/co-catalyst combinations for photo-catalytic water splitting. The hole energy necessary to thermodynamically drive the reaction is employed as descriptor for the screening process. Using this protocol and hybrid-level density-functional theory we show that water oxidation on bare TiO2 surfaces is thermodynamically more complex than previously thought. This motivates a screening for suitable co-catalysts for this half-reaction, which w…
In recent years, single-atom catalysts attracted lots of attention because of their high catalytic activity, selectivity, stability, maximum atom utilization, exceptional performance, and low cost. Single-atom catalyst contains isolated individual atom which are coordinated with the surface atoms of support such as a metal oxide or 2d - materials. In this review article, we present the advancement in single-atom catalysis in recent years with a focus on the various synthesis methods and their application in catalytic reactions. We also demonstrate the reaction mechanism of a single-atom cataly…
The complexity of the topological and combinatorial configuration space of MXenes can give rise to gigantic design challenges that cannot be addressed through traditional experimental or routine theoretical approaches. To this end, we establish a robust and more broadly applicable multistep workflow from the toolbox of supervised machine learning (ML) algorithms for predicting the hydrogen evolution reaction (HER) activity over 4,500 MM$^{\prime}$XT$_2$-type MXenes, where 25\% of the material space (1125 systems) is randomly selected to evaluate the HER performance using density functional the…
Three different catalysts (Fe, Ni, Co nitrates dissolved in ethanol) were patterned on a SiO2/Si substrate and multi-wall carbon nanotubes were grown by catalytic decomposition of acetylene. We compare the growth of the carbon nanostructures in the temperature range between 580C and 1000C. With our experimental set-up the catalyst solutions of cobalt and nickel were found to be less efficient than the one of iron. An optimal production of multi-wall nanotubes was observed at temperatures between 650C and 720C with the iron solution as catalyst. We found a tendency towards thicker structures wi…
We have developed a thermodynamic model of the catalytic growth of multiwall carbon nanotubes from hydrocarbon precursors at elevated temperature. Using this model we have computed the heat distribution, and carbon concentration in the catalyst. Calculations delivered a analytical formula for the growth time and growth rate. We find that the growth is mainly driven by a concentration gradient within the catalyst, rather than a temperature gradient.
Catalysts for oxygen reduction and evolution reactions are at the heart of key renewable energy technologies including fuel cells and water splitting. Despite tremendous efforts, developing oxygen electrode catalysts with high activity at low costs remains a grand challenge. Here, we report a hybrid material of Co3O4 nanocrystals grown on reduced graphene oxide (GO) as a high-performance bi-functional catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). While Co3O4 or graphene oxide alone has little catalytic activity, their hybrid exhibits an unexpected, surprisin…
Addition of only 1% of acetylene into ethanol was found to enhance the growth rate of singlewalled carbon nanotubes (SWNTs) by up to ten times. Since acetylene is a byproduct of the thermal decomposition of ethanol, this suggests an alternative fast reaction pathway to the formation of SWNTs from ethanol via byproducts of decomposition. This accelerated growth, however, only occurred in the presence of ethanol, whereas pure acetylene at the same partial pressure resulted in negligible growth and quickly deactivated the catalyst. The dormant catalyst could be revived by reintroduction of ethano…
The family of MAX phases and their derivative MXenes are continuously growing in terms of both crystalline and composition varieties. In the last couple of years, several breakthroughs have been achieved that boosted the synthesis of novel MAX phases with ordered double transition metals and, consequently, the synthesis of novel MXenes with a higher chemical diversity and structural complexity, rarely seen in other families of two-dimensional (2D) materials. Considering the various elemental composition possibilities, surface functional tunability, various magnetic orders, and large spin$-$orb…
The search for highly efficient and low-cost catalysts is one of the main driving forces in catalytic chemistry. Current strategies for the catalyst design focus on increasing the number and activity of local catalytic sites, such as the edge-sites of molybdenum disulfides in the hydrogen evolution reaction (HER). Here, we propose and demonstrate a different principle that goes beyond local site optimization by utilizing topological electronic states, a global property of the material, to spur catalytic activity. For HER, we have found excellent catalysts among the transition-metal monopnictid…
Topological quantum catalysts (TQCs), where metallic surface states from nontrivial band topology serve as the mechanism to favor heterogeneous catalysis processes, have been well demonstrated in three dimensional (3D) examples but have been rarely discussed in 2D scale. Here, we develop a design scheme to realize 2D TQCs with showing traversing nodal line at the Brillouin zone boundary, large Fermi arc on the edge, and nearly zero Gibbs free energy (ΔGH*) for hydrogen evolution reaction (HER). We demonstrate the 2D Cu2C2N4 sheet is a such example. The material manifests an open nodal line tra…
Recently, two kinds of mesoporous catalysts with high propylene selectivity in propane dehydrogenation (PDH) process has been successfully synthesized. The first proposed catalyst is SAPO-34 molecular sieve with hierarchical tuned nanostructure. The second catalyst is a novel bi-phase SAPO-34/ZSM-5 zeolite hierarchical composite utilized with TPA-SAPO-34 exchanged core cystals being wrapped by ZSM-5 zeolite particles. In this contribution, the physico-chemical properties of the catalysts were analyzed by XRD, FESEM and N2 adsorption-desorption techniques and their catalytic activity and life t…
Topological states of matter and their corresponding properties are classical research topics in condensed matter physics. Quite recently, the application of materials that feature these states has been extended to the field of electrochemical catalysis and become an emerging research topic that is receiving increasing interest. In particular, several recent experimental studies performed on topological semimetals have already revealed high catalytic performance towards hydrogen evolution reaction (HER), strongly promoting acceptance of the fresh concept of the topological catalyst. This emerg…
Heterogeneous catalysts consisting of supported metallic nanoparticles typically derive exceptional catalytic activity from their large proportion of under-coordinated surface sites which promote adsorption of reactant molecules. Simultaneously, these high energy surface configurations are unstable, leading to nanoparticle growth or degradation, and eventually a loss of catalytic activity. Surface morphology of catalytic nanoparticles is paramount to catalytic activity, selectivity, as well as degradation rates, however, it is well-known that harsh reaction conditions can cause the surface str…
Among transition metal dichalcogenides (TMdCs) as alternatives for Pt-based catalysts, metallic-TMdCs catalysts have highly reactive basal-plane but are unstable. Meanwhile, chemically stable semiconducting-TMdCs show limiting catalytic activity due to their inactive basal-plane. Here, we propose metallic vanadium sulfide (VSn) nanodispersed in a semiconducting MoS2 film (V-MoS2) as an efficient catalyst. During synthesis, vanadium atoms are substituted into hexagonal monolayer MoS2 to form randomly distributed VSn units. The V-MoS2 film on a Cu electrode exhibits Pt-scalable catalytic perform…
The discovery of metals as catalytic centers for nitrogen reduction reactions has stimulated great enthusiasm for single-atom catalysts. However, the poor activity and low selectivity of available SACs are far away from the industrial requirement. Through the high throughout first principles calculations, the doping engineering can effectively regulate the NRR performance of b-Sb monolayer. Especially, the origin of activated N2 is revealed from the perspective of the electronic structure of the active center. Among the 24 transition metal dopants, Re@Sb and Tc@Sb showed the best NRR catalytic…
The phase diagram of surface structures for the model catalyst RuO2(110) in contact with a gas environment of O2 and CO is calculated by density-functional theory and atomistic thermodynamics. Adsorption of the reactants is found to depend crucially on temperature and partial pressures in the gas phase. Assuming that a catalyst surface under steady-state operation conditions is close to a constrained thermodynamic equilibrium, we are able to rationalize a number of experimental findings on the CO oxidation over RuO2(110). We also calculated reaction pathways and energy barriers. Based on the v…
The discovery of new catalysts that are efficient, sustainable, and low-cost is a major research endeavor for many industrial chemical processes. This requires an understanding and determination of the catalytic origins for the given catalysts, which still remains a challenge. Here we describe a novel method to identify new catalysts based on searching for crystalline symmetry-protected obstructed atomic insulators (OAIs) that have metallic surface states on otherwise semiconducting or insulating compounds. The Wannier charge centers in OAIs are pinned by symmetries at some empty Wyckoff posit…
For decades of catalysis research, the d-band center theory that correlates the d-band center and the adsorbate binding energy has successfully enabled the accelerated discovery of novel catalyst materials. Recent studies indicate that, on top of the d-band center value, the full consideration of the d-band shapes describing higher moments of the d-band as well as sp-band properties can help better capturing surface reactivity. However, the density-of-states (DOS) patterns themselves have never been used as a descriptor in combined computational-experimental studies. Here, we propose the full …
Computer Vision and Learning Systems, Department of Electrical Engineering (ISY) & AI4X（计算机视觉与学习系统，电气工程系（ISY）及AI4X）；Materials Design Division, Department of Physics, Chemistry and Biology (IFM)（材料设计分校，物理、化学与生物系（IFM））；Wallingenberg Initiative Materials Science for Sustainability (WISE)（瓦伦贝格可持续材料科学倡议（WISE））
As emerging atomically ultrathin metal compounds, MXenes show great promise for catalysts and nanoelectronics applications due to the abundant surface terminations and high metallic conductivity. However, the tendency of the interlayer adhesion and suffering from environmental disturbances significantly limit their endurance and efficiency. Herein via conducting first-principles calculations, we explore surface passivation and exfoliation of MXene via polymers which have been experimentally proven to promote the performance. Nine kinds of monomers together with the typical MXene Ti3C2T2 (T= No…
Pristine graphene is thought lack of catalytic activity up to date, although using graphene-plus-heteroatom materials as catalysts has become a subject of intensive research because it can be metal saving, eco-friendly and ultimately sustainable. Here we report observations of catalytic reactions of high-quality, clean, pristine graphene when immersed into organics containing C=O bonds, like acetone, acetic acid and acetaldehyde. The C=O bonds were found to break and form polymers including polyethers. The reaction rate is highly temperature dependent. The reaction products mainly physically a…
$\textit{In situ}$ environmental transmission electron microscopy (ETEM) is a powerful tool for observing structural modifications taking place in heterogeneous catalysts under reaction conditions. However, to strengthen the link between catalyst structure and functionality, an $\textit{operando}$ measurement must be performed in which reaction kinetics and catalyst structure are simultaneously determined. To determine chemical kinetics for gas-phase catalysis, it is necessary to develop a reliable chemical engineering model to describe catalysis as well as heat and mass transport processes wi…
The practical use of nanoparticle superlattices (NPSLs) which are of great interest as materials with designed functionalities is often limited by their lack of structural stability under various utilization conditions. Here, we report a new method for directly synthesizing NPSL fully embedded in hierarchically porous silica which provides exceptional stability and efficient pathways for reactant molecules, making the NPSL highly efficient catalyst. The superlattices made of 12 nm gold nanoparticles exhibit exceptionally high catalytic activity for CO oxidation at low temperature, showing high…
The ability to efficiently evolve hydrogen via electrocatalysis at low overpotentials holds tremendous promise for clean energy. Hydrogen evolution reaction (HER) can be easily achieved from water if a voltage above the thermodynamic potential of the HER is applied. Large overpotentials are energetically inefficient but can be lowered with expensive platinum based catalysts. Replacement of Pt with inexpensive, earth abundant electrocatalysts would be significantly beneficial for clean and efficient hydrogen evolution. Towards this end, promising HER characteristics have been reported using 2H …
Machine learning is ideally suited for the pattern detection in large uniform datasets, but consistent experimental datasets on catalyst studies are often small. Here we demonstrate how a combination of machine learning and first-principles calculations can be used to extract knowledge from a relatively small set of experimental data. The approach is based on combining a complex machine-learning model trained on a computational library of transition-state energies with simple linear regression models of experimental catalytic activities and selectivities from the literature. Using the combined…
Reducible oxides are widely used catalyst supports that can increase oxidation reaction rates by transferring their lattice oxygen at the metal-support interface. The interfacial oxidation process is typically described in terms of a Mars-van Krevelen mechanism. However, many outstanding questions remain unanswered regarding the atomic-scale structure and dynamic meta-stability (i.e., fluxional behavior) of the interface $\textit{during catalysis}$. Here, we employ aberration-corrected $\textit{operando}$ electron microscopy to visualize the structural dynamics occurring at and near Pt/CeO$_{2…
The conversion of natural gas (methane) to ethane and ethylene (OCM: oxidative coupling of methane) facilitates its transportation and provides a way to synthesize higher value chemicals. The search for high-performance catalysts to achieve this conversion is the main scope of most corresponding studies in the field of OCM. Here, we present a general data-driven strategy for the search of novel catalytic materials, focusing particularly on materials useful for the OCM reaction. Our strategy is based on consistent experimental measurements and includes ab initio thermodynamics calculations and …
A new dual plasma coating process to produce platinum-free catalysts for the oxygen reduction reaction in a fuel cell is introduced. The catalysts thus produced were analysed with various methods. Electrochemical characterisation was carried out by cyclic voltammetry, rotating ring- and rotating ring-disk electrode. The surface porosity of the different catalysts thus obtained was characterised with the nitrogen gas adsorption technique and scanning electron microscopy was used to determine the growth mechanisms of the films. It is shown that catalytically active compounds can be produced with…
In an attempt to understand why catalytic methods for the growth of boron nitride nanotubes work much worse than for their carbon counterparts, we use first-principles calculations to study the energetics of elemental reactions forming N2, B2 and BN molecules on an iron catalyst. We observe that in the case of these small molecules, the catalytic activity is hindered by the formation of B2 on the iron surface. We also observe that the local morphology of a step edge present in our nanoparticle model stabilizes the boron nitride molecule with respect to B2 due to the ability of the step edge to…
Unraveling a descriptor that is correlated with catalytic reactivity is essential for fast screening for the optimal catalysts for a given catalytic reaction. Herein, we propose bond-derived orbitalwise coordination number ($\overline{CN}^α$, $α$= $s$ or $d$) as a simple and accurate descriptor used for transition metal (TM) oxides that takes into account both geometrical and electronic structures around active sites, and avoids excessive computation burden. This descriptor has a strong scaling relation with the activity in oxygen electrochemistry, enabling us to readily screen for the optimal…
Fuel cells in vehicles are the leading cause of carbon monoxide emissions. CO is one of the most dangerous gases in the atmosphere, as it binds to the hemoglobin in blood cells 200 times easier than O2. As the amount of CO in the blood stream increases, the level of oxygen decreases, which can lead to many neurological problems. To reduce the amount of CO in the atmosphere, scientists have focused on the adsorption of oxygen. The best substrates used today are platinum and palladium monolayers, which are very expensive. Because of this, researchers have searched for cheap materials, such as Mo…
Metal heteroatoms dispersed in nitrogen-doped graphene display promising catalytic activity for fuel cell reactions such as the hydrogen evolution reaction (HER). Here we explore the effects of dopant concentration on the synergistic catalytic behaviour of a paired metal atom active site comprised of Co and Pt atoms. The metals are coordinated to six atoms in a vacancy of N-doped graphene. We find that HER activity is enhanced with increasing N concentration, where the free energy of hydrogen atom adsorption ranges from 0.23 to -0.42 eV as the doping changes from a single N atom doped in the p…
For electrochemical hydrogen evolution reaction (HER), developing high-performance catalysts without containing precious metals has been a major research focus in the current. Herein, we show the feasibility of HER catalytic enhancement in Ni-based materials based on topological engineering from hybrid Weyl states. Via a high-throughput computational screening from 140 000 materials, we identify a chiral compound NiSi is a hybrid Weyl semimetal (WSM) with showing bulk type-I and type-II Weyl nodes and long surface Fermi arcs near the Fermi level. Sufficient evidences verify that topological ch…
MoS2 nanoparticles are proven catalysts for processes such as hydrodesulphurization and hydrogen evolution, but unravelling their atomic-scale structure under catalytic working conditions has remained significantly challenging. Ambient pressure X-ray Photoelectron Spectroscopy (AP-XPS) allows us to follow in-situ the formation of the catalytically relevant MoS2 edge sites in their active state. The XPS fingerprint is described by independent contributions to the Mo3d core level spectrum whose relative intensity is sensitive to the thermodynamic conditions. Density Functional Theory (DFT) is us…
The surface reconstruction of the Fe catalyst films due to high temperature processing in hydrogen prior to nanotube nucleation and its effect on the growth morphologies of partially filled carbon nanotubes (CNTs) synthesized using atmospheric pressure chemical vapor deposition (APCVD) of propane was investigated. Results show that pre-heating of the catalyst film deeply influences the particle size distribution, which governs the growth morphologies of the corresponding CNTs. The distribution of the catalyst particles over the Si substrate was analyzed before and after the heat treatment by a…
Molybdenum Disulfide (MoS$_2$) has been recognized as a potential substitution of Platinum (Pt) for electrochemical hydrogen evolution reaction (HER). However, the broad adoption of MoS$_2$ is hindered by its limited number of active sites and relatively low inherent electrical conductivity. In this work, we demonstrated a synergistic enhancement of both active site exposure and electrical conductivity by a one-step solvothermal synthesis technique. The 1T-phase enriched MoS$_2$ was directly formed on the titanium carbide (Ti$_3$C$_2$Tx, MXene) with carbon nanotubes (CNTs) acting as crosslinks…
Nominally undoped silicon nanowires (NW) were grown by catalytic chemical vapor deposition. The growth process was optimized to control the NWs diameters by using different Au catalyst thicknesses on amorphous SiO2, Si3N4, or crystalline-Si substrates. For SiO2 substrates an Ar plasma treatment was used to homogenize the catalyst coalescence, and thus the NWs diameter. Furthermore, planar field effect transistors (FETs) were fabricated by implementing 10 to 30 nm thin nominally undoped Si-NWs as the active region. Various silicides were investigated as Schottky-barrier source and drain contact…
The present study reports the catalytic action of two-dimensional (2D) layered materials (MoS2 and WS2) for improving the de/re-hydrogenation kinetics of MgH2. The MgH2 start desorbing at 277 C with a hydrogen storage capacity of 5.95 wt% in the presence of WS2 catalyst whereas onset desorption temperature of MgH2 catalyzed by MoS2 is 330 C. The MgH2-WS2 absorbed hydrogen ~ 3.72 wt% within 1.3 minutes at 300 C under 13 atm hydrogen pressure and it desorbed ~5.57 wt% within 20 minutes at 300 C under 1 atm hydrogen pressure. We have performed 25 cycles of dehydrogenation (under 1 atm hydrogen pr…
Topological materials are recently regarded as the idea catalysts due to the protected surface metallic states and high carrier mobility, however the fundamental mechanism and the underlying relationship between the catalytic performance and topological states are in debate. Here, by means of symmetry analysis and first-principles calculations, we discover that the electride material of C12A7 hosts the multiple-fold fermions due to the interstitial-electrons, with the sixfold- and fourfold- degenerate points locating at high symmetric points near the Fermi energy, which are identified as the u…
