Research

●    Industrial Catalysis

●    Photocatalysis

●    Electrocatalysis

●    Interfacial & Surface Catalysis

●    Batteries

Industrial Catalysis

Industrial catalysis has been applied to the production of more than 90% of chemicals. The subject of industrial catalysis has been systematically studied in aspects of catalyst design, transport/reaction analysis and process optimization. At nanoscale, high-performance catalysts are constructed based on first-principle calculations and catalytic experiments, and microscopic reaction kinetic mechanism and models are established in combination with in-situ characterizations. At meso-scale, multiphase models are developed to analyze transport and reaction processes within reactors. At macro-scale, big data modelling methods and in-line measurement techniques are employed to enable the design and optimization of complex reactors and processes. We expect to provide a research paradigm via integrating the research from "nanoscale catalysis" to "reactor/process optimization" for the industrial catalysis.

1. Alkane dehydrogenation

Light alkenes, such as ethylene, propylene, and butylene, are extensively used as chemical building blocks in the chemical industry. The catalytic dehydrogenation of light alkanes into the corresponding alkenes is of great interest due to the limited petroleum reserves and development of the exploitation technology for shale gas. The current commercial processes are still restricted by the catalyst performance and cost. We aim to develop eco-friendly and cost-efficient catalysts to boost the alkene production industry. Current projects include:
●Rational design and fabrication of efficient Pt-based catalysts and alternative catalysts
●Determination of structure-performance relationship for designed catalysts using density functional theory (DFT) calculations and operando/in situ characterization techniques
●Scale-up production of dehydrogenation catalysts with well-defined structures

2. COx and Alkyne hydrogenation

CO2 hydrogenation is an approach to produce clean fuels and valuable chemicals from a gas mixture of CO2 and H2, which can reduce the use of fossil fuels and control greenhouse gas emissions. However, the reaction route of CO2 hydrogenation is rather complex due to the requirement of the activation of both CO2 and H2. We aim to understand the influence of geometric and electronic structures on the reaction pathway and develop efficient catalysts with desired selectivity. Current projects include:
●Rational design of interfacial and synergistic structures for catalysts
●Electronic interaction between oxide and support
●Identification of the reaction pathway and active sites in CO2 hydrogenation

Polyethylene accounts for nearly 30% of the total production of plastics worldwide, which reaches more than 300 million tons every year. Prior to polymerization, the selective hydrogenation of the remnant acetylene (ca. 1%) in the raw ethylene stream is necessary. Traditionally, the hydrogenation of acetylene has been mostly catalyzed by noble metals supported on metal oxides or zeolites. We aim to reveal the influence of activation and transport of hydrogen species on this selective hydrogenation process. Current projects include:
●Encapsulation structure of catalysts for the activation and spillover of hydrogen
●Influence of electronic structures on the hydrogen activation process with higher catalytic performance

3. Chemical looping process

It is desirable to perform energy or materials conversions through clean, safe and energy-efficient process technologies. Chemical looping processes can achieve the selective activation of C-H bonds, avoid the safety problems caused by co-feeding of oxygen with alkane and eliminate/alleviate the needs for separation, which leads to lower costs, emissions and energy penalties. Redox catalysts (usually metal oxides) that can selectively oxidize fuels using lattice oxygen play a central role in this technology. We aim to develop efficient redox catalysts with proper oxygen species for chemical looping alkane (e.g., methane, propane) conversion for the efficient production of propylene, syngas and hydrogen. Current projects include:
●Design of redox catalysts via structure engineering to upgrade light alkane for the production of value-added chemicals
●Determination of the active site for alkane activation and identification of active oxygen species for selective conversion or complete oxidation of alkanes by in situ techniques
●Kinetics of lattice oxygen for surface reaction and bulk oxygen migration

4. Reactor design and process optimization

The multi-scale nature of reaction and transport in multiphase renders the difficulty in the design and optimization of chemical processes. The rapid development of multiphase modelling methods and in-line measurement technologies provides feasible approaches to bridge the micro-scale multiphase behaviours and structures to the macro-scale processes performance. In addition, the chemical processes can be intensified by external fields, such as light, electricity and plasma, to promote the performance and energy efficiency. We aim to combine the multiphase modelling, in-line measurement and intensification methods to design and optimize chemical reactors and processes. Current projects include:
●Development of multiphase modelling methods
●Construction of in-line measurement for multiphase reactors
●Process intensification via external fields

Photocatalysis

1. Hydrogen production via photoelectrochemical water splitting

Hydrogen generation from photoelectrochemical (PEC) water splitting represents a holy grail in chemistry and energy science. Compared to bulk semiconductors, nanostructured photoelectrodes  could potentially improve the solar-to-hydrogen conversion efficiency due to their large surface area and short diffusion length for minority carriers. We conduct a new line of research directed towards (1) designing PEC devices using dense and vertically aligned metal oxide nanowire arrays as photoanodes, and (2) creating novel hybrid semiconductors with high solar-to-hydrogen conversion efficiency. 
Current projects include:
●Rational design of self-assembled colloids as photoanodes
●Hierarchical bottom-up approach to a new generation of photoanodes
●Fabrication of nanostructured photoanodes via reactive angle deposition

2. Fuel generation by photocatalytic CO2 reduction

Utilizing the abundant solar energy to convert CO2 into fuels such as methane or methanol could provide a convenient means of energy storage and positively impact the global carbon balance. There remain great challenges in the selectivity of photogenerated electrons for CO2 reduction in the presence of H2O. We are interested in (1) designing online detection devices for CO2 photoreduction (2) creating novel semiconductors with high conversion efficiency and selectivity for CO2 reduction. Current projects include:
●Rational design of mesoporous photoanodes to achieve a high adsorption ability of CO2
●Investigation on the relationship between selectivity and CO2 reduction co-catalyst
●Surface modification of the photocatalysts to reduce the activation energy or overpotential for CO2 reduction

3. Well-controlled nanocatalysts for fuel cell-related reactions

Fuel cells are receiving extensive attention owing to their numerous advantages, including high efficiency, high specific energy density, and low pollution. The performance of a fuel cell is directly determined by the activity of its catalysts. Among various types of catalysts, the platinum-group metals (PGMs) are broadly used as the key catalysts in several kinds of fuel cells, such as proton exchange membrane fuel cell (PEMFC), direct formic acid fuel cell (DFAFC) and direct methanol fuel cell (DMFC). However, their low abundance in the earth’s crust and their ever increasing prices have created a major roadblock for the large-scale commercialization of PGMs-related fuel cells. We aimed to develop more active catalysts through tuning the utilization efficiency, exposed surfaces and composition of Pt- or Pd- based nanocrystals. The mechanism for relationship between the well-controlled nanocrystals and their performance in fuel cell-related electrocatalytic reactions are carefully investigated via DFT calculations. Current projects include:
●Shape-controlled synthesis of Pd-Au alloy with high-energy surfaces
●Preparation of Pt-based core-shell structure to achieve a high mass activity towards oxidation reduction reaction
●Rational design of Pt-free catalysts for oxidation reduction reaction

4. Selective oxidation of alcohols via photocatalysis

Selective oxidation of alcohols with molecular oxygen (O2) is an essential process for the synthesis of various chemicals. Traditionally, toxic oxidants or harsh conditions are needed during the oxidation of alcohols. The photocatalytic selective oxidation provides an alternative green and sustainable process for the chemical synthesis under mild conditions. We aim to develop photocatalysts with wide absorption range of light and efficient separation of electrons and holes. In addition, we also work on the mechanism illustration of selective oxidation via various photocatalysts, which is helpful to design catalysts with high efficiency rationally. Current project includes:
●Photocatalytic oxidation of benzyl alcohol over metal-oxides with expanded absorption range of irradiation
●Mechanism of photocatalytic oxidation over various photocatalysts
●Photocatalytic oxidation over oxides with oxidation and reduction cocatalysts which could improve the separation of electrons and holes.

Electrocatalysis

1. Electrocatalytic CO2 Reduction

Facing the shortage of fossil resources and the environmental issues caused by excessive CO2 emission, it is of great significance to develop strategies to utilize CO2 in a sustainable manner. We are investigating electrocatalytic CO2 reduction technologies to synthesize carbon-neutral chemical fuels and feedstocks using renewable electricity. We perform theoretical calculations to screen novel catalysts. The results of theoretical calculations guide the synthesis of catalysts with finely tuned reaction sites and high performance. Based on the development of outstanding electrocatalysts, we optimize the integrating methods of the catalysts into electrolyzers. We design gas diffusion electrodes and membrane electrode assemblies to enable CO2 reduction to achieve industrially relevant performance metrics.
Current projects include:
●Synthesis of highly active electrocatalysts to convert CO2 into chemical feedstocks (e.g., ethylene, syngas) and renewable fuels (e.g., methane, methanol, and ethanol)
●Investigation of electrocatalysts and manipulation of multi-physics fields within CO2 reduction devices
●Design of novel reactors to break mass transfer limitations for the industrialization of CO2 reduction systems

2. Electrochemical Production of Green Hydrogen

Green hydrogen is the key to build up a carbon-neutral society. Electrochemical water splitting by renewable electricity is a promising way to obtain green hydrogen. We focus on the synthesis of inexpensive transition metal-based electrocatalysts to replace precious metal electrocatalysts for water splitting. Meanwhile, we study the direct electrolysis of seawater and design stable and corrosion-resistant catalysts to produce hydrogen. In order to improve the current density and stability of water splitting systems, our team also investigate the behavior of bubbles in the electrolyte. By regulating the fluid flow pattern, we seek to reduce the ohmic resistance drop, improve the energy conversion efficiency, and eventually achieve the long-term operation of the hydrogen production devices.
Current projects include:
●Electrochemical oxygen evolution reaction catalyzed by inexpensive transition metal-based electrocatalysts
●Corrosion-resistant catalysts for the electrolysis of seawater
●Modulation of the growth and desorption behaviors of bubbles

Interfacial & Surface Catalysis

1. Mechanistic study by computational chemistry

Exploration of catalyst reaction mechanisms is of fundamental importance in improving known catalysts or designing new catalysts. In recent years, a great number of the catalytic processes have been computationally studied using Density Functional Theory (DFT) calculations and other relative methods. Along with the development of computational chemistry methods, parallel computing and high-performance computing cluster, state-of-the-art computational chemistry researches not only uncover the essence of a known catalytic process, but also are used as a fast and low-cost pre-screening technic to assist new catalyst design.Currently, we are focusing on following projects

i. Mechanistic research on propane dehydrogenation to propylene: In order to gain deeper understanding of dehydrogenations of saturated hydrocarbons, we selected propane dehydrogenation reactions as our model reactions, which was catalyzed by Pt based catalyst. To facilitate determination of systematic trends in the propane dehydrogenationon Pt based catalyst, we will first investigate propane dehydrogenation on flat and stepped Pt and PtM alloy surfaces as well as interfaces of metal oxides, including MgO, Al2O3, and TiO2. They were selected for initial study as supports with at least one surface which matches the shape and size of the Pt(100) or Pt(111) surface. In a practical sense, the matched lattice dimensions provide a more uniform geometry between systems, thus facilitating initial development of correlations and Brønsted–Evans–Polanyi (BEP) relationships at the metal/support interfaces. By systematically permuting the alloy metal and nature of the substrates, we will establish correlations and reactivity patterns, including the development of BEP relationships. In the future, the analysis can be extended to other supported transition metal catalysts, and "volcano" relationships can be constructed between the predicted activity of different metal alloy/support structures and key catalytic parameters that are identified through the analysis.

ii. Development of Global Optimization Algorithm: One challenge to build a realistic catalyst model is to determining its most stable structure (global minimum) or set of lowest energy structures of a catalyst under reaction conditions. Although local minimum optimization technics have already been well developed, it could not guarantee the optimized structure to be the most stable one in case with complicated environment, like high adsorbate coverage, surface reconstruction, etc. Ideally, the global minimum can be located by exploring the whole potential energy surface with conducting numbers of local optimizations. We are interested in improvement of global optimization efficiency by reducing the number of local optimizations to obtain the desired global minimum with advanced computational algorithms like genetic algorithm, machine learning.

iii. Electrocatalysis of CO2 reduction: The insights of catalytic structures and exploration of candidate catalysts in our group mainly also focus on (photo)electrocatalysis for CO2 reduction (CO2RR). For example, atomic structure motifs for product-specific active sites on OD-Cu catalysts OD-Cu are detected by the molecular dynamic simulation with neural network (NN) potential. As for metal oxide, the surface defect was utilized to detect the regulatory factor for the catalytic performance. In detail, surface defects can control the adsorption strength of key intermediates of CO2RR by surface hydroxyl (Cu2O) or oxygen vacancies (SnOx), thereby providing theoretical guidance for improving the selectivity of target products. Our further analysis would continue to explore the influence on the reaction mechanisms around the regulation of surface morphology, electronic structure and extend to the model construction consistent with the realistic environment.

iv. Machine learning potentials: Recently, the data-driven ML technique is emerging as a useful tool and surrogate model to accelerate the time-consuming simulation. Machine learning potentials (MLP), which directly learns the potential surface from ab initio calculations, have been developed to act as an energy calculator with high accuracy while maintaining the large speedup. Using MLP as a surrogate model, not only the thermodynamics for active sites, the evaluation of kinetic properties like reaction rate can also be accelerated. MLP can significantly extend the spatial and time scale of atomistic simulations, providing more opportunities to simulate large-scale catalyst systems while maintaining high accuracy. Besides, MLP can accelerate enhanced sampling simulations to predict the long-time-scale surface reaction using ab initio calculation. In our group, we tend to develop and apply MLP to accelerate the time-consuming, large-scale, and long-term simulation of catalytic system.

Batteries

Current state of the art in battery technology significantly sacrifices high energy density, high power density and security. Energy storage devices such as advanced batteries, including Li-ion, Na-ion, K-ion batteries, lithium–sulfur batteries batteries, are important for portable electronics, vehicle electrification and smart grid. We develop novel materials including electrodes, electrolytes, binders, current collectors to address scientific problems, and improve the critical performance parameters related to energy storage such as energy density, power density, safety, cycle and calendar life and cost.
Current projects include:
●P-based anode for Li-ion, Na-ion, K-ion batteries
●Other Li-ion battery anodes: Si, Bi, Li
●Li-ion battery cathodes: metal oxides, sulfur
●Li-ion battery electrolytes: esters, ethers, high concentration salts
●Zn-ion battery: Zn metal anodes and metal oxides cathodes, respectively