After Professor Zhang joined CityU in 2019, 100 papers have been published/accepted. The representative research work mainly related to preparation and applications of noble metal nanomaterials are listed below.

1. We report the controlled synthesis of Pd-based alloy nanoparticles with an unconventional hexagonal close-packed (hcp, 2H type) crystal phase via a facile and general seeded method. By using 2H-Pd nanoparticles as seeds, 2H-PdCu alloy nanoparticles with tunable Cu contents can be synthesized by simply changing the reaction time. Furthermore, by using the aforementioned 2H-PdCu nanoparticles as templates, the partial galvanic replacement of Cu atoms by Pt can be conducted to induce the incorporation of Pt into PdCu nanoparticles, realizing the preparation of trimetallic PdCuPt alloy nanomaterials with unconventional 2H phase (Figure 1). As a proof-of-concept application, the as-synthesized Pd-based alloy nanoparticles can be used as highly efficient catalysts towards electrochemical oxygen reduction reaction (ORR) in alkaline media. In particular, the trimetallic 2H-PdCuPt alloy nanoparticles exhibit excellent catalytic activity, outperforming most of the reported Pdbased ORR electrocatalysts in alkaline electrolytes. This work was published in Journal of the American Chemical Society, 2021, 143, 17292-17299.

Figure 1 Schematic illustration of the seeded synthesis of 2H-PdCu and 2H-PdCuPt alloy nanoparticles from 2H-Pd (left) and ORR performance of various catalysts. (right)

2. We develop a facile two-step method for the lattice expansion on specific facets, i.e., Pt(100) and Pt(111), of Pt catalysts. We first prepare the Pd@Pt core-shell nanoparticles exposed with the Pt(100) and Pt(111) facets via the Pd-seeded epitaxial growth and then convert the Pd core to PdH_0.43 by the hydrogen intercalation. The lattice expansion of the Pd core induces the lattice enlargement of the Pt shell, which can significantly promote the alcohol oxidation reaction (AOR) on both Pt(100) and Pt(111) facets. Impressively, the Pt mass-specific activities of 32.51 A mg^Pt-1 for methanol oxidation and 14.86 A mg^Pt-1 for ethanol oxidation, which are 41.15 and 25.19 times those of the commercial Pt/C catalyst, respectively, have been achieved on the Pt(111) facet. Density functional theory (DFT) calculations indicate that the remarkably improved catalytic performance on both Pt(100) and Pt(111) facets through the lattice expansion arises from the enhanced OH adsorption. This work not only paves the way for lattice engineering on specific facets of nanomaterials to enhance their electrocatalytic activity but also offers a promising strategy towards the rational design and preparation of highly efficient catalysts. This work was published in Journal of the American Chemical Society, 2021, 143, 11262-11270.

3. We report a chemical method for synthesis of hierarchical Rh nanostructures composed of ultrathin nanosheets, composed of hexagonal close-packed structure embedded with nanodomains that adopt a vacated Barlow packing with ordered vacancies. The obtained Rh nanostructures exhibit remarkably enhanced electrocatalytic activity and stability toward the hydrogen evolution reaction (HER) in alkaline media. Theoretical calculations reveal that the exceptional electrocatalytic performance of Rh nanostructures originates from their unique vacancy structures, which facilitate the adsorption and dissociation of H₂O in the HER. This work was published in Science Advances, 2021, 7, eabd6647.

4. Two-dimensional (2D) square-like Au nanosheets with an unconventional 2H/face-centered cubic (fcc) heterophase, composing of two pairs of opposite edges with 2H/fcc heterophase and fcc phase, respectively, and two 2H/fcc heterophase basal planes, are prepared and then used as templates to grow one-dimensional (1D) Rh nanorods. The effect of different phases in different regions of the Au templates on the overgrowth of Rh nanorods has been systematically investigated. By tuning the reaction conditions, three types of 1D/2D Rh-Au heterostructures are prepared. In the type A heterostructure, Rh nanorods only grow on the fcc defects including stacking faults and/or twin boundaries (denoted as fccSF/T) and 2H phases in two 2H/fcc edges of the Au nanosheet. In the type B heterostructure, Rh nanorods grow on the fcc-SF/T and 2H phases in two 2H/fcc edges and two 2H/fcc basal planes of the Au nanosheet. In the type C heterostructure, Rh nanorods grow on four edges and two basal planes of the Au nanosheet. Furthermore, the type C heterostructure shows promising performance towards the electrochemical HER in acidic media, which is among the best reported Rh-based and other noblemetal-based HER electrocatalysts. This work was published in Journal of the American Chemical Society, 2021, 143, 4387–4396.

Figure 2 Preparation and structure characterization of o-Pd@Pt and o-PdH_0.43@Pt NPs.

5. We report a general, facile wet-chemical method to synthesize ultrathin amorphous/crystalline heterophase Rh and Rhbased bimetallic alloy nanosheets, including RhCu, RhZn, and RhRu. Impressively, the amorphous/crystalline heterophase Rh nanosheets exhibit enhanced catalytic activity toward the direct synthesis of indole compared to the crystalline counterpart. Importantly, the obtained amorphous/crystalline heterophase RhCu alloy nanosheets can further enhance the selectivity to indole of >99.9% and the conversion is 100%. Our work demonstrates the importance of PEN and metal alloying in the rational design of Rh-based catalysts, providing a new avenue for developing efficient metal nanocatalysts for the fine chemical synthesis. This work was published in Advanced Materials, 2021, 33, 2006711.

6. We report the crystal-phase engineering of Co and Ni nanostructures by quasi-epitaxial growth. Specifically, by using 4H-Au nanoribbons as templates, 4H-Au@14H-Co nanostructures are successfully prepared via the quasi-epitaxial growth. Notably, due to the large lattice mismatch between Co and Au, ordered misfit dislocations are formed at the Au/Co interface, resulting in a new phase of Co, namely 14H. By fine tuning the reaction conditions, Co can form branches or thin layers on 4HAu surfaces, resulting in two kinds of nanostructures that are denoted as 4H-Au@14H-Co nanobranches and 4H-Au@14HCo nanoribbons, respectively. Moreover, by using a different synthetic method, 4H-Au@2H-Co nanoribbons with thicker Co layer are also prepared, in which ordered dislocations with different periodicity are observed. This method can also be used to prepare 4H-Au@2H-Ni nanoribbons. This work was published in Advanced Materials, 2021, 33, 2007140.

7. We report the preparation of Pd nanoparticles with an unconventional hexagonal close-packed (2H type) phase, referred to as 2H-Pd nanoparticles, via a controlled phase transformation of amorphous Pd nanoparticles. Impressively, by using the 2HPd nanoparticles as seeds, Au nanomaterials with different crystal phases epitaxially grow on the specific exposed facets of the 2H-Pd, i.e., face-centered cubic (fcc) Au (fcc-Au) on the (002) h facets of 2H-Pd while 2H-Au on the other exposed facets, to achieve well-defined fcc-2H-fcc heterophase Pd@Au core-shell nanorods. Moreover, through such unique facet-directed crystalphase-selective epitaxial growth, a series of unconventional fcc2H-fcc heterophase core-shell nanostructures, including Pd@Ag, Pd@Pt, Pd@PtNi, and Pd@PtCo, have also been prepared. Impressively, the fcc-2H-fcc heterophase Pd@Au nanorods show excellent performance toward the electrochemical carbon dioxide reduction reaction (CO₂RR) for production of carbon monoxide with Faradaic efficiencies of over 90% in an exceptionally wide applied potential window from -0.9 to -0.4 V (versus the reversible hydrogen electrode), which is among the best reported CO2RR catalysts in H-type electrochemical cells. This work was published in Journal of the American Chemical Society, 2020, 142, 18971–18980.

8. We report a one-pot wet-chemical synthesis of well-defined heterophase fcc-2H-fcc gold nanorods at mild conditions. Single particle-level experiments and theoretical investigations reveal that the heterophase gold nanorods demonstrate a distinct optical property compared to that of the conventional fcc gold nanorods. Moreover, the heterophase gold nanorods possess superior electrocatalytic activity for the CO₂RR over their fcc counterparts under ambient conditions. First-principles calculations suggest that the boosted catalytic performance stems from the energetically favourable adsorption of reaction intermediates, endowed by the unique heterophase characteristic of gold nanorods. This work was published in Nature Communications, 2020, 11, 3293.

9. We report the crystal phase-controlled synthesis of PtCu alloy shells on 4H Au nanoribbons, referred to as 4H-Au nanoribbons, to form the 4H-Au@PtCu core–shell nanoribbons. By tuning the thickness of PtCu, 4H-PtCu and fcc-PtCu alloy shells are successfully grown on the 4H-Au nanoribbon cores. This thickness-dependent phase-controlled growth strategy can also be used to grow PtCo alloys with 4H or fcc phase on 4HAu nanoribbons. Significantly, when used as electrocatalysts for the ethanol oxidation reaction (EOR) in alkaline media, the 4H-Au@4H-PtCu nanoribbons show much better EOR performance than the 4H-Au@fcc-PtCu nanoribbons, and both of them possess superior performance compared to the commercial Pt black. Our study provides a strategy on phasecontrolled synthesis of nanomaterials used for crystal phasedependent applications. This work was published in Nano Research, 2020, 13, 1970–1975.

10. We report a crystal phase-dependent catalytic behavior of Cu, after the successful synthesis of high-purity 4H Cu and heterophase 4H/fcc Cu using the 4H and 4H/fcc Au as templates, respectively. Remarkably, the obtained unconventional crystal structures of Cu exhibit enhanced overall activity and higher ethylene (C₂H₄) selectivity in CO₂RR compared to the fcc Cu. Density functional theory calculations suggest that the 4H phase and 4H/fcc interface of Cu favor the C₂H₄ formation pathway compared to the fcc Cu, leading to the crystal phase-dependent C₂H₄ selectivity. This study demonstrates the importance of crystal phase engineering of metal nanocatalysts for electrocatalytic reactions, offering a new strategy to prepare novel catalysts with unconventional phases for various applications. This work was published in Journal of the American Chemical Society, 2020, 142, 12760–12766.

11. We report the synthesis of binary (Pd-P) crystalline@amorphous heterostructured nanoplates using Cu_3−χP nanoplates as templates via a cation exchange method. The obtained nanoplate possesses a crystalline core and an amorphous shell with the same elemental components, referred to as c-Pd-P@a-Pd-P. Moreover, the obtained c-Pd-P@a-Pd-P nanoplates can serve as templates to be further alloyed with Ni, forming ternary (Pd-Ni-P) crystalline@amorphous heterostructured nanoplates, referred to as c-Pd-NiP@a-Pd-Ni-P. The atomic content of Ni in the c-Pd-NiP@a-Pd-Ni-P nanoplates can be tuned in the range from 9.47 to 38.61 at%. When used as a catalyst, the c-Pd-Ni-P@a-Pd-Ni-P nanoplates with 9.47 at% Ni exhibit excellent electrocatalytic activity toward EOR, showing a high mass current density up to 3.05 A mg^Pd−1, which is 4.5 times that of the commercial Pd/ C catalyst (0.68 A mg^Pd−1). This work was published in Advanced Materials, 2020, 32, 2000482.

12. We report a systematic study of surface-plasmon-driven hot-electron-induced photocatalytic reduction of paranitrothiophenol (pNTP) to p,p'-dimercaptoazobenzene under visible light on Au nanostructures with different crystal phases by in-situ surface-enhanced Raman spectroscopy (SERS). Our results indicate that the photocatalytic rate of unconventional 4H Au is nearly 6-8 times that of conventional fcc Au, suggesting the greater activity of hot electrons on 4H Au. Further electrochemical reductions of pNTP on the 4H and fcc Au nanostructures in aqueous solutions also confirm the higher catalytic activity of the 4H Au. Our study demonstrates that the synthesis of Au nanomaterials with controlled crystal phases paves the way for developing highly efficient catalyst. This work was published in ACS Materials Letters, 2020, 2, 409–414.

13. We report a systematic study on the thermal effect of ultrathin 4H Au nanoribbons by using in situ transmission electron microscopy characterization. Despite Rayleigh instability upon moderate electron beam-induced heating below ~400 K, there is no obvious phase transition observed in ultrathin 4H Au nanoribbons. However, phase transition from 4H to fcc occurs when heating temperature reaches ~800 K, which agrees well with the molecular dynamics simulations. This work provides key insights into the thermal stability of ultrathin 4H Au nanostructures and may facilitate their future practical application in nanoelectronics, plasmonics, and catalysis. This work was published in Matter, 2020, 2, 519–521.

14. We report the discovery of a unique thiol molecule, namely bismuthiol I, which can induce the transformation of Pd nanomaterials from fcc phase into amorphous phase without destroying their integrity. This ligand-induced amorphization is realized by post-synthetic ligand exchange under ambient conditions, and is applicable to fcc Pd nanomaterials with different capping ligands. Importantly, the obtained amorphous Pd nanoparticles exhibit remarkably enhanced activity and excellent stability toward electrocatalytic hydrogen evolution reaction (HER) in acidic solution. This work provides a facile and effective method for preparing amorphous Pd nanomaterials, and demonstrates their promising electrocatalytic application. This work was published in Advanced Materials, 2020, 32, 1902964.

Reference 

1. Ge, Y, Wang, X, Huang, B, Huang, Z, Chen, B, Ling, C, Liu, J, Liu, G, Zhang, J, Wang, G, Chen, Y, Li, L, Liao, L, Wang, L, Yun, Q, Lai, Z, Lu, S, Luo, Q, Wang, J, Zheng, Z & Zhang, H 2021, 'Seeded Synthesis of Unconventional 2H-Phase Pd Alloy Nanomaterials for Highly Efficient Oxygen Reduction', Journal of the American Chemical Society, vol. 143, no. 41, pp. 17292-17299.

2. Liu, G, Zhou, W, Ji, Y, Chen, B, Fu, G, Yun, Q, Chen, S, Lin, Y, Yin, P-F, Cui, X, Liu, J, Meng, F, Zhang, Q, Song, L, Gu, L & Zhang, H 2021, 'Hydrogen-Intercalation-Induced Lattice Expansion of Pd@Pt Core- Shell Nanoparticles for Highly Efficient Electrocatalytic Alcohol Oxidation', Journal of the American Chemical Society, vol. 143, no. 29, pp. 11262–11270.

3. Zhang, Z, Liu, G, Cui, X, Gong, Y, Yi, D, Zhang, Q, Zhu, C, Saleem, F, Chen, B, Lai, Z, Yun, Q, Cheng, H, Huang, Z, Peng, Y, Fan, Z, Li, B, Dai, W, Chen, W, Du, Y, Ma, L, Sun, C-J, Hwang, I, Chen, S, Song, L, Ding, F, Gu, L, Zhu, Y & Zhang, H 2021, 'Evoking ordered vacancies in metallic nanostructures toward a vacated Barlow packing for high-performance hydrogen evolution', Science Advances, vol. 7, no. 13, eabd6647.

4. Liu, J, Niu, W, Liu, G, Chen, B, Huang, J, Cheng, H, Hu, D, Wang, J, Liu, Q, Ge, J, Yin, P, Meng, F, Zhang, Q, Gu, L, Lu, Q & Zhang, H 2021, 'Selective Epitaxial Growth of Rh Nanorods on 2H/fcc Heterophase Au Nanosheets to Form 1D/2D Rh-Au Heterostructures for Highly Efficient Hydrogen Evolution', Journal of the American Chemical Society, vol. 143, no. 11, pp. 4387–4396.

5. Ge, J, Yin, P, Chen, Y, Cheng, H, Liu, J, Chen, B, Tan, C, Yin, P-F, Zheng, H-X, Li, Q-Q, Chen, S, Xu, W, Wang, X, Wu, G, Sun, R, Shan, X-H, Hong, X & Zhang, H 2021, 'Ultrathin Amorphous/Crystalline Heterophase Rh and Rh Alloy Nanosheets as Tandem Catalysts for Direct Indole Synthesis', Advanced Materials, vol. 33, no. 9, 2006711.

6. Cheng, H, Yang, N, Liu, X, Guo, Y, Liu, B, Yang, J, Chen, Y, Chen, B, Fan, Z, Lu, Q, Yuan, S, Wang, J, Gu, L & Zhang, H 2021, 'Quasi-Epitaxial Growth of Magnetic Nanostructures on 4H-Au Nanoribbons', Advanced Materials, vol. 33, no. 1, 2007140.

7. Liu, J, Huang, J, Niu, W, Tan, C & Zhang, H 2021, 'Unconventional-Phase Crystalline Materials Constructed from Multiscale Building Blocks', Chemical Reviews, vol. 121, no. 10, pp. 5830–5888.

8. Ge, Y, Huang, Z, Ling, C, Chen, B, Liu, G, Zhou, M, Liu, J, Zhang, X, Cheng, H, Liu, G, Du, Y, Sun, C-J, Tan, C, Huang, J, Yin, P, Fan, Z, Chen, Y, Yang, N & Zhang, H 2020, 'Phase-Selective Epitaxial Growth of Heterophase Nanostructures on Unconventional 2H-Pd Nanoparticles', Journal of the American Chemical Society, vol. 142, no. 44, pp. 18971-18980.

9. Fan, Z, Bosman, M, Huang, Z, Chen, Y, Ling, C, Wu, L, Akimov, YA, Laskowski, R, Chen, B, Ercius, P, Zhang, J, Qi, X, Goh, MH, Ge, Y, Zhang, Z, Niu, W, Wang, J, Zhang, H & Zhang, H 2020, 'Heterophase fcc-2H-fcc gold nanorods', Nature Communications, vol. 11, 3293.

10. Wang, J, Zhang, J, Liu, G, Ling, C, Chen, B, Huang, J, Liu, X, Li, B, Wang, AL, Hu, Z, Zhou, M, Chen, Y, Cheng, H, Liu, J, Fan, Z, Yang, N, Tan, C, Gu, L, Wang, J & Zhang, H 2020, 'Crystal phase-controlled growth of PtCu and PtCo alloys on 4H Au nanoribbons for electrocatalytic ethanol oxidation reaction', Nano Research, vol. 13, no. 7, pp. 1970–1975.

11. Chen, Y, Fan, Z, Wang, J, Ling, C, Niu, W, Huang, Z, Liu, G, Chen, B, Lai, Z, Liu, X, Li, B, Zong, Y, Gu, L, Wang, J, Wang, X & Zhang, H 2020, 'Ethylene Selectivity in Electrocatalytic CO2 Reduction on Cu Nanomaterials: A Crystal Phase-Dependent Study', Journal of the American Chemical Society, vol. 142, no. 29, pp. 12760−12766.

12. Yin, P-F, Zhou, M, Chen, J, Tan, C, Liu, G, Ma, Q, Yun, Q, Zhang, X, Cheng, H, Lu, Q, Chen, B, Chen, Y, Zhang, Z, Huang, J, Hu, D, Wang, J, Liu, Q, Luo, Z, Liu, Z, Ge, Y, Wu, X-J, Du, X-W & Zhang, H 2020, 'Synthesis of Palladium-Based Crystalline@Amorphous Core–Shell Nanoplates for Highly Efficient Ethanol Oxidation', Advanced Materials, vol. 32, no. 21, 2000482.

13. Huang, J, Niu, W, Li, C, Tan, C, Yin, P, Cheng, H, Hu, Z, Yang, N, He, Q, Nam, G-H & Zhang, H 2020, 'In-Situ Probing of Crystal-Phase-Dependent Photocatalytic Activities of Au Nanostructures by Surface-Enhanced Raman Spectroscopy', ACS Materials Letters, vol. 2, no. 4, pp. 409-414.

14. Li, P, Han, Y, Zhou, X, Fan, Z, Xu, S, Cao, K, Meng, F, Gao, L, Song, J, Zhang, H & Lu, Y 2020, 'Thermal Effect and Rayleigh Instability of Ultrathin 4H Hexagonal Gold Nanoribbons', Matter, vol. 2, no. 3, pp. 658-665.

15. Cheng, H, Yang, N, Liu, G, Ge, Y, Huang, J, Yun, Q, Du, Y, Sun, C-J, Chen, B, Liu, J & Zhang, H 2020, 'Ligand-Exchange-Induced Amorphization of Pd Nanomaterials for Highly Efficient Electrocatalytic Hydrogen Evolution Reaction', Advanced Materials, vol. 32, no. 11, 1902964.

16. Cui, X, Zhang, Z, Gong, Y, Saleem, F, Chen, B, Du, Y, Lai, Z, Yang, N, Li, B, Gu, L & Zhang, H 2020, 'Defect-Rich, Candied Haws-Shaped AuPtNi Alloy Nanostructures for Highly Efficient Electrocatalysis', CCS Chemistry, vol. 2, no. 1, pp. 24-30.