Honors & Awards


  • National scholarship for graduate students, Chinese Government (Oct 2016)
  • MRS Graduate Student Award Gold, Materials Research Society (Dec 2016)

Professional Education


  • Joint Doctor of Philosophy, University of Toronto, Energy conversion and storage (2017)
  • Doctor of Philosophy, Tianjin University (2017)
  • Bachelor of Engineering, Tianjin University (2012)

All Publications


  • Highly Emissive Green Perovskite Nanocrystals in a Solid State Crystalline Matrix. Advanced materials Quan, L. N., Quintero-Bermudez, R., Voznyy, O., Walters, G., Jain, A., Fan, J. Z., Zheng, X., Yang, Z., Sargent, E. H. 2017; 29 (21)

    Abstract

    Perovskite nanocrystals (NCs) have attracted attention due to their high photoluminescence quantum yield (PLQY) in solution; however, maintaining high emission efficiency in the solid state remains a challenge. This study presents a solution-phase synthesis of efficient green-emitting perovskite NCs (CsPbBr3 ) embedded in robust and air-stable rhombic prism hexabromide (Cs4 PbBr6 ) microcrystals, reaching a PLQY of 90%. Theoretical modeling and experimental characterization suggest that lattice matching between the NCs and the matrix contribute to improved passivation, while spatial confinement enhances the radiative rate of the NCs. In addition, dispersing the NCs in a matrix prevents agglomeration, which explains their high PLQY.

    View details for DOI 10.1002/adma.201605945

    View details for PubMedID 28370565

  • Enhanced Solar-to-Hydrogen Generation with Broadband Epsilon-Near-Zero Nanostructured Photocatalysts. Advanced materials Tian, Y., García de Arquer, F. P., Dinh, C., Favraud, G., Bonifazi, M., Li, J., Liu, M., Zhang, X., Zheng, X., Kibria, M. G., Hoogland, S., Sinton, D., Sargent, E. H., Fratalocchi, A. 2017

    Abstract

    The direct conversion of solar energy into fuels or feedstock is an attractive approach to address increasing demand of renewable energy sources. Photocatalytic systems relying on the direct photoexcitation of metals have been explored to this end, a strategy that exploits the decay of plasmonic resonances into hot carriers. An efficient hot carrier generation and collection requires, ideally, their generation to be enclosed within few tens of nanometers at the metal interface, but it is challenging to achieve this across the broadband solar spectrum. Here the authors demonstrate a new photocatalyst for hydrogen evolution based on metal epsilon-near-zero metamaterials. The authors have designed these to achieve broadband strong light confinement at the metal interface across the entire solar spectrum. Using electron energy loss spectroscopy, the authors prove that hot carriers are generated in a broadband fashion within 10 nm in this system. The resulting photocatalyst achieves a hydrogen production rate of 9.5 µmol h-1  cm-2 that exceeds, by a factor of 3.2, that of the best previously reported plasmonic-based photocatalysts for the dissociation of H2 with 50 h stable operation.

    View details for DOI 10.1002/adma.201701165

    View details for PubMedID 28481018

  • Modest Oxygen-Defective Amorphous Manganese-Based Nanoparticle Mullite with Superior Overall Electrocatalytic Performance for Oxygen Reduction Reaction SMALL Dong, C., Liu, Z., Liu, J., Wang, W., Cui, L., Luo, R., Guo, H., Zheng, X., Qiao, S., Du, X., Yang, J. 2017; 13 (16)

    Abstract

    Manganese-based oxides have exhibited high promise as noncoinage alternatives to Pt/C for catalyzing oxygen reduction reaction (ORR) in basic solution and a mix of Mn3+/4+ valence is believed to be vital in achieving optimum ORR performance. Here, it is proposed that, distinct from the most studied perovskites and spinels, Mn-based mullites with equivalent molar ratio of Mn3+ and Mn4+ provide a unique platform to maximize the role of Mn valence in facile ORR kinetics by introducing modest content of oxygen deficiency, which is also beneficial to enhanced catalytic activity. Accordingly, amorphous mullite SmMn2 O5-δ nanoparticles with finely tuned concentration of oxygen vacancies are synthesized via a versatile top-down approach and the modest oxygen-defective sample with an Mn3+ /Mn4+ ratio of 1.78, i.e., Mn valence of 3.36 gives rise to a superior overall ORR activity among the highest reported for the family of Mn-based oxides, comparable to that of Pt/C. Altogether, this study opens up great opportunities for mullite-based catalysts to be a cost-effective alternative to Pt/C in diverse electrochemical energy storage and conversion systems.

    View details for DOI 10.1002/smll.201603903

    View details for Web of Science ID 000399455900012

    View details for PubMedID 28195444

  • Sulfur-Modulated Tin Sites Enable Highly Selective Electrochemical Reduction of CO2 to Formate Joule Zheng, X., De luna, P., de Arquer, F., Zhang, B., Becknell, N., Cui, Y., Du, X., Yang, P., Sargent, E. 2017
  • Theory-driven design of high-valence metal sites for water oxidation confirmed using in situ soft X-ray absorption Nature Chemistry Zheng, X., Zhang, B., De Luna, P., Liang, Y., Comin, R., Du, X., Sargent, E. 2017

    View details for DOI 10.1038/NCHEM.2886

  • Enhanced electrocatalytic CO2 reduction via field-induced reagent concentration NATURE Liu, M., Pang, Y., Zhang, B., De Luna, P., Voznyy, O., Xu, J., Zheng, X., Dinh, C. T., Fan, F., Cao, C., de Arquer, F. P., Safaei, T. S., Mepham, A., Klinkova, A., Kumacheva, E., Filleter, T., Sinton, D., Kelley, S. O., Sargent, E. H. 2016; 537 (7620): 382-?
  • Engineering surface atomic structure of single-crystal cobalt (II) oxide nanorods for superior electrocatalysis NATURE COMMUNICATIONS Ling, T., Yan, D., Jiao, Y., Wang, H., Zheng, Y., Zheng, X., Mao, J., Du, X., Hu, Z., Jaroniec, M., Qiao, S. 2016; 7

    Abstract

    Engineering the surface structure at the atomic level can be used to precisely and effectively manipulate the reactivity and durability of catalysts. Here we report tuning of the atomic structure of one-dimensional single-crystal cobalt (II) oxide (CoO) nanorods by creating oxygen vacancies on pyramidal nanofacets. These CoO nanorods exhibit superior catalytic activity and durability towards oxygen reduction/evolution reactions. The combined experimental studies, microscopic and spectroscopic characterization, and density functional theory calculations reveal that the origins of the electrochemical activity of single-crystal CoO nanorods are in the oxygen vacancies that can be readily created on the oxygen-terminated {111} nanofacets, which favourably affect the electronic structure of CoO, assuring a rapid charge transfer and optimal adsorption energies for intermediates of oxygen reduction/evolution reactions. These results show that the surface atomic structure engineering is important for the fabrication of efficient and durable electrocatalysts.

    View details for DOI 10.1038/ncomms12876

    View details for Web of Science ID 000385384100010

    View details for PubMedID 27650485

    View details for PubMedCentralID PMC5035995

  • Strongly Coupled Nafion Molecules and Ordered Porous CdS Networks for Enhanced Visible-Light Photoelectrochemical Hydrogen Evolution ADVANCED MATERIALS Zheng, X., Song, J., Ling, T., Hu, Z. P., Yin, P., Davey, K., Du, X., Qiao, S. 2016; 28 (24): 4935-4942

    Abstract

    Strongly coupled Nafion molecules and ordered porous CdS networks are fabricated for visible-light photoelectrochemical (PEC) hydrogen evolution. The Nafion layer coating shifts the band position of CdS upward and accelerates charge transfer in the photoelectrode/electrolyte interface. It is highly expected that the strong coupling effect between organic and inorganic materials will provide new routes to advance PEC water splitting.

    View details for DOI 10.1002/adma.201600437

    View details for Web of Science ID 000378939200020

    View details for PubMedID 27038367

  • ZnFe2O4 Leaves Grown on TiO2 Trees Enhance Photoelectrochemical Water Splitting SMALL Zheng, X., Dinh, C., de Arquer, F. P., Zhang, B., Liu, M., Voznyy, O., Li, Y., Knight, G., Hoogland, S., Lu, Z., Du, X., Sargent, E. H. 2016; 12 (23): 3181-3188

    Abstract

    TiO2 has excellent electrochemical properties but limited solar photocatalytic performance in light of its large bandgap. One important class of visible-wavelength sensitizers of TiO2 is based on ZnFe2 O4 , which has shown fully a doubling in performance relative to pure TiO2 . Prior efforts on this important front have relied on presynthesized nanoparticles of ZnFe2 O4 adsorbed on a TiO2 support; however, these have not yet achieved the full potential of this system since they do not provide a consistently maximized area of the charge-separating heterointerface per volume of sensitizing absorber. A novel atomic layer deposition (ALD)-enhanced synthesis of sensitizing ZnFe2 O4 leaves grown on the trunks of TiO2 trees is reported. These new materials exhibit fully a threefold enhancement in photoelectrochemical performance in water splitting compared to pristine TiO2 under visible illumination. The new materials synthesis strategy relies first on the selective growth of FeOOH nanosheets, 2D structures that shoot off from the sides of the TiO2 trees; these templates are then converted to ZnFe2 O4 with the aid of a novel ALD step, a strategy that preserves morphology while adding the Zn cation to achieve enhanced optical absorption and optimize the heterointerface band alignment.

    View details for DOI 10.1002/smll.201600534

    View details for Web of Science ID 000378654700013

    View details for PubMedID 27145726

  • Homogeneously dispersed multimetal oxygen-evolving catalysts. Science Zhang, B., Zheng, X., Voznyy, O., Comin, R., Bajdich, M., García-Melchor, M., Han, L., Xu, J., Liu, M., Zheng, L., García de Arquer, F. P., Dinh, C. T., Fan, F., Yuan, M., Yassitepe, E., Chen, N., Regier, T., Liu, P., Li, Y., De Luna, P., Janmohamed, A., Xin, H. L., Yang, H., Vojvodic, A., Sargent, E. H. 2016; 352 (6283): 333-337

    Abstract

    Earth-abundant first-row (3d) transition metal-based catalysts have been developed for the oxygen-evolution reaction (OER); however, they operate at overpotentials substantially above thermodynamic requirements. Density functional theory suggested that non-3d high-valency metals such as tungsten can modulate 3d metal oxides, providing near-optimal adsorption energies for OER intermediates. We developed a room-temperature synthesis to produce gelled oxyhydroxides materials with an atomically homogeneous metal distribution. These gelled FeCoW oxyhydroxides exhibit the lowest overpotential (191 millivolts) reported at 10 milliamperes per square centimeter in alkaline electrolyte. The catalyst shows no evidence of degradation after more than 500 hours of operation. X-ray absorption and computational studies reveal a synergistic interplay between tungsten, iron, and cobalt in producing a favorable local coordination environment and electronic structure that enhance the energetics for OER.

    View details for DOI 10.1126/science.aaf1525

    View details for PubMedID 27013427

  • Carbon Nanotube Reinforced CdSe Inverse Opal with Crack-Free Structure and High Conductivity for Photovoltaic Applications ADVANCED MATERIALS INTERFACES Zheng, X., Qin, W., Ling, T., Pan, C., Du, X. 2015; 2 (2)