Tong Zhou

Bio: Tong Zhou is an academic researcher from State University of New York System. The author has contributed to research in topics: Topological insulator & Spintronics. The author has an hindex of 20, co-authored 47 publications receiving 1759 citations. Previous affiliations of Tong Zhou include Fudan University & University at Buffalo.

Reduced Mesoporous Co3O4 Nanowires as Efficient Water Oxidation Electrocatalysts and Supercapacitor Electrodes

Abstract: While electrochemical water splitting is one of the most promising methods to store light/electrical energy in chemical bonds, a key challenge remains in the realization of an efficient oxygen evolution reaction catalyst with large surface area, good electrical conductivity, high catalytic properties, and low fabrication cost. Here, a facile solution reduction method is demonstrated for mesoporous Co3O4 nanowires treated with NaBH4. The high-surface-area mesopore feature leads to efficient surface reduction in solution at room temperature, which allows for retention of the nanowire morphology and 1D charge transport behavior, while at the same time substantially increasing the oxygen vacancies on the nanowire surface. Compared to pristine Co3O4 nanowires, the reduced Co3O4 nanowires exhibit a much larger current of 13.1 mA cm-2 at 1.65 V vs reversible hydrogen electrode (RHE) and a much lower onset potential of 1.52 V vs RHE. Electrochemical supercapacitors based on the reduced Co3O4 nanowires also show a much improved capacitance of 978 F g-1 and reduced charge transfer resistance. Density-functional theory calculations reveal that the existence of oxygen vacancies leads to the formation of new gap states in which the electrons previously associated with the Co-O bonds tend to be delocalized, resulting in the much higher electrical conductivity and electrocatalytic activity.

Nanoparticle Superlattices as Efficient Bifunctional Electrocatalysts for Water Splitting

Abstract: The solar-driven water splitting process is highly attractive for alternative energy utilization, while developing efficient, earth-abundant, bifunctional catalysts for both oxygen evolution reaction and hydrogen evolution reaction has remained as a major challenge. Herein, we develop an ordered CoMnO@CN superlattice structure as an efficient bifunctional water-splitting electrocatalyst, in which uniform Co–Mn oxide (CoMnO) nanoparticles are coated with a thin, continuous nitrogen-doped carbon (CN) framework. The CoMnO nanoparticles enable optimized OER activity with effective electronic structure configuration, and the CN framework serves as an excellent HER catalyst. Importantly, the ordered superlattice structure is beneficial for enhanced reactive sites, efficient charge transfer, and structural stability. This bifunctional superlattice catalyst manifests optimized current densities and electrochemical stability in overall water splitting, outperforming most of the previously reported single- or bifun...

Strong magnetization and Chern insulators in compressed graphene / CrI 3 van der Waals heterostructures

Abstract: Graphene-based heterostructures are a promising material system for designing the topologically nontrivial Chern insulating devices. Recently, a two-dimensional monolayer ferromagnetic insulator ${\mathrm{CrI}}_{3}$ was successfully synthesized in experiments [B. Huang et al., Nature (London) 546, 270 (2017)]. Here, these two interesting materials are proposed to build a heterostructure $(\mathrm{Gr}\text{/}{\mathrm{CrI}}_{3})$. Our first-principles calculations show that the system forms a van der Waals (vdW) heterostructure, which is relatively facilely fabricated in experiments. A Chern insulating state is acquired in the $\mathrm{Gr}\text{/}{\mathrm{CrI}}_{3}$ heterostructure if the vdW gap is compressed to a distance between about 3.3 and 2.4 \AA{}, corresponding to a required external pressure between about 1.4 and 18.3 GPa. Amazingly, very strong magnetization (about 150 meV) is found in graphene, induced by the substrate ${\mathrm{CrI}}_{3}$, despite the vdW interactions between them. A low-energy effective model is employed to understand the mechanism. The work functions, contact types, and band alignments of the $\mathrm{Gr}\text{/}{\mathrm{CrI}}_{3}$ heterostructure system are also studied. Our work demonstrates that the $\mathrm{Gr}\text{/}{\mathrm{CrI}}_{3}$ heterostructure is a promising system to observe the quantum anomalous Hall effect at high temperatures (up to 45 K) in experiments.

Li2TiSiO5: a low potential and large capacity Ti-based anode material for Li-ion batteries

Abstract: To date, anode materials for lithium-ion batteries (LIBs) have been dominated by carbonaceous materials, which have a low intercalation potential but easily allow lithium dendrites to form under high current density, leading to a safety risk. The other anode material, the “zero-strain” spinel-structured Li4Ti5O12, with a ∼1.5 V vs. Li+/Li intercalation potential, exhibits excellent cycling stability and avoids the issues of dendrite growth and Li plating. The low capacity and high voltage of Li4Ti5O12, however, result in low energy density. Herein, we report a new and environmentally friendly anode material, Li2TiSiO5, which delivers a capacity as high as 308 mA h g−1, with a working potential of 0.28 V vs. Li+/Li, and excellent cycling stability. The lithium-storage mechanism of this material is also proposed based on the combination of in situ synchrotron X-ray diffraction, neutron powder diffraction with Fourier density mapping, ex situ X-ray absorption near edge structure analysis, ex situ transmission electron microscopy, and density-functional theory calculations with the projector-augmented-wave formalism. The lithium-storage mechanism of this material is shown to involve a two-electron (Ti4+/Ti2+ redox) conversion reaction between TiO and Li4SiO4.

Bio-Inspired Leaf-Mimicking Nanosheet/Nanotube Heterostructure as a Highly Efficient Oxygen Evolution Catalyst

Abstract: Plant leaves represent a unique 2D/1D heterostructure for enhanced surface reaction and efficient mass transport. Inspired by plant leaves, a 2D/1D CoOx heterostructure is developed that is composed of ultrathin CoOx nanosheets further assembled into a nanotube structure. This bio-inspired architecture allows a highly active Co2+ electronic structure for an efficient oxygen evolution reaction (OER) at the atomic scale, ultrahigh surface area (371 m2 g−1) for interfacial electrochemical reaction at the nanoscale, and enhanced transport of charge and electrolyte over CoOx nanotube building blocks at the microscale. Consequently, this CoOx nanosheet/nanotube heterostructure demonstrates a record-high OER performance based on cobalt compounds reported so far, with an onset potential of ≈1.46 V versus reversible hydrogen electrode (RHE), a current density of 51.2 mA cm−2 at 1.65 V versus RHE, and a Tafel slope of 75 mV dec−1. Using the CoOx nanosheet/nanotube catalyst and a Pt-mesh, a full water splitting cell with a 1.5-V battery is also demonstrated.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Plasma-Engraved Co3 O4 Nanosheets with Oxygen Vacancies and High Surface Area for the Oxygen Evolution Reaction.

Abstract: Co3O4, which is of mixed valences Co2+ and Co3+, has been extensively investigated as an efficient electrocatalyst for the oxygen evolution reaction (OER). The proper control of Co2+/Co3+ ratio in Co3O4 could lead to modifications on its electronic and thus catalytic properties. Herein, we designed an efficient Co3O4-based OER electrocatalyst by a plasma-engraving strategy, which not only produced higher surface area, but also generated oxygen vacancies on Co3O4 surface with more Co2+ formed. The increased surface area ensures the Co3O4 has more sites for OER, and generated oxygen vacancies on Co3O4 surface improve the electronic conductivity and create more active defects for OER. Compared to pristine Co3O4, the engraved Co3O4 exhibits a much higher current density and a lower onset potential. The specific activity of the plasma-engraved Co3O4 nanosheets (0.055 mA cm−2BET at 1.6 V) is 10 times higher than that of pristine Co3O4, which is contributed by the surface oxygen vacancies.

Transition-Metal (Co, Ni, and Fe)-Based Electrocatalysts for the Water Oxidation Reaction

Abstract: Increasing energy demands and environment awareness have promoted extensive research on the development of alternative energy conversion and storage technologies with high efficiency and environmental friendliness. Among them, water splitting is very appealing, and is receiving more and more attention. The critical challenge of this renewable-energy technology is to expedite the oxygen evolution reaction (OER) because of its slow kinetics and large overpotential. Therefore, developing efficient electrocatalysts with high catalytic activities is of great importance for high-performance water splitting. In the past few years, much effort has been devoted to the development of alternative OER electrocatalysts based on transition-metal elements that are low-cost, highly efficient, and have excellent stability. Here, recent progress on the design, synthesis, and application of OER electrocatalysts based on transition-metal elements, including Co, Ni, and Fe, is summarized, and some invigorating perspectives on the future developments are provided.

Non-Noble Metal-based Carbon Composites in Hydrogen Evolution Reaction: Fundamentals to Applications.

Abstract: Hydrogen has been hailed as a clean and sustainable alternative to finite fossil fuels in many energy systems. Water splitting is an important method for hydrogen production in high purity and large quantities. To accelerate the hydrogen evolution reaction (HER) rate, it is highly necessary to develop high efficiency catalysts and to select a proper electrolyte. Herein, the performances of non-noble metal-based carbon composites under various pH values (acid, alkaline and neutral media) for HER in terms of catalyst synthesis, structure and molecular design are systematically discussed. A detailed analysis of the structure-activity-pH correlations in the HER process gives an insight on the origin of the pH-dependence for HER, and provide guidance for future HER mechanism studies on non-noble metal-based carbon composites. Furthermore, this Review gives a fresh impetus to rational design of high-performance noble-metal-free composites catalysts and guide researchers to employ the established electrocatalysts in proper water electrolysis technologies.

Defect Chemistry of Nonprecious-Metal Electrocatalysts for Oxygen Reactions

Abstract: Oxygen electrocatalysis, including the oxygen-reduction reaction (ORR) and oxygen-evolution reaction (OER), is a critical process for metal-air batteries Therefore, the development of electrocatalysts for the OER and the ORR is of essential importance Indeed, various advanced electrocatalysts have been designed for the ORR or the OER; however, the origin of the advanced activity of oxygen electrocatalysts is still somewhat controversial The enhanced activity is usually attributed to the high surface areas, the unique facet structures, the enhanced conductivities, or even to unclear synergistic effects, but the importance of the defects, especially the intrinsic defects, is often neglected More recently, the important role of defects in oxygen electrocatalysis has been demonstrated by several groups To make the defect effect clearer, the recent development of this concept is reviewed here and a novel principle for the design of oxygen electrocatalysts is proposed An overview of the defects in carbon-based, metal-free electrocatalysts for ORR and various defects in metal oxides/selenides for OER is also provided The types of defects and controllable strategies to generate defects in electrocatalysts are presented, along with techniques to identify the defects The defect-activity relationship is also explored by theoretical methods