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Highly porous non-precious bimetallic electrocatalysts for efficient hydrogen evolution.

Lu Q, Hutchings GS, Yu W, Zhou Y, Forest RV, Tao R, Rosen J, Yonemoto BT, Cao Z, Zheng H, Xiao JQ, Jiao F, Chen JG - Nat Commun (2015)

Bottom Line: Although both copper and titanium are known to be poor hydrogen evolution catalysts, the combination of these two elements creates unique copper-copper-titanium hollow sites, which have a hydrogen-binding energy very similar to that of platinum, resulting in an exceptional hydrogen evolution activity.In addition, the hierarchical porosity of the nanoporous copper-titanium catalyst also contributes to its high hydrogen evolution activity, because it provides a large-surface area for electrocatalytic hydrogen evolution, and improves the mass transport properties.Moreover, the catalyst is self-supported, eliminating the overpotential associated with the catalyst/support interface.

View Article: PubMed Central - PubMed

Affiliation: 1] Center for Catalytic Science and Technology, Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, USA [2] Department of Chemical Engineering, Columbia University, New York, New York 10027, USA.

ABSTRACT
A robust and efficient non-precious metal catalyst for hydrogen evolution reaction is one of the key components for carbon dioxide-free hydrogen production. Here we report that a hierarchical nanoporous copper-titanium bimetallic electrocatalyst is able to produce hydrogen from water under a mild overpotential at more than twice the rate of state-of-the-art carbon-supported platinum catalyst. Although both copper and titanium are known to be poor hydrogen evolution catalysts, the combination of these two elements creates unique copper-copper-titanium hollow sites, which have a hydrogen-binding energy very similar to that of platinum, resulting in an exceptional hydrogen evolution activity. In addition, the hierarchical porosity of the nanoporous copper-titanium catalyst also contributes to its high hydrogen evolution activity, because it provides a large-surface area for electrocatalytic hydrogen evolution, and improves the mass transport properties. Moreover, the catalyst is self-supported, eliminating the overpotential associated with the catalyst/support interface.

No MeSH data available.


XRD and TEM characterization.(a) The XRD patterns of np-CuTi and Ti-free np-Cu. Inset: the enlarged region of Cu (111) diffraction peaks, with the dotted line indicating the peak position of pure Cu. (b) High-angle annular dark-field (HAADF) scanning (S)TEM image of a cross-sectioned np-CuTi sample prepared using FIB technique. Scale bar, 1 μm. (c), HAADF STEM image with a higher magnification. The box indicates the region selected for EELS study. Scale bar, 50 nm. (d–f) The contrast image of the selected region for EELS mapping study and its corresponding Cu (e) and Ti (f) maps. Scale bar, 50 nm. (g) High-resolution TEM image with visible lattice fringes. Inset: The Fourier transform confirms that np-CuTi is composed of an extended crystalline network. Scale bar, 2 nm.
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f3: XRD and TEM characterization.(a) The XRD patterns of np-CuTi and Ti-free np-Cu. Inset: the enlarged region of Cu (111) diffraction peaks, with the dotted line indicating the peak position of pure Cu. (b) High-angle annular dark-field (HAADF) scanning (S)TEM image of a cross-sectioned np-CuTi sample prepared using FIB technique. Scale bar, 1 μm. (c), HAADF STEM image with a higher magnification. The box indicates the region selected for EELS study. Scale bar, 50 nm. (d–f) The contrast image of the selected region for EELS mapping study and its corresponding Cu (e) and Ti (f) maps. Scale bar, 50 nm. (g) High-resolution TEM image with visible lattice fringes. Inset: The Fourier transform confirms that np-CuTi is composed of an extended crystalline network. Scale bar, 2 nm.

Mentions: The PXRD data for np-CuTi (Fig. 3a) suggested a similar crystal structure with that of the bulk Cu-Ti alloys. A small unit cell expansion (Supplementary Table 2) was also observed because ofTi substitution. The atomic ratio of Ti to (Cu+Ti) of np-CuTi was verified to be about 5 at. % by EDX analysis (Supplementary Fig. 5), mimicking the optimal composition of Cu95Ti5 from the bulk Cu-Ti alloy study. The consistency in their surface conditions was also confirmed using XPS characterizations (Supplementary Fig. 6). To further study the structure of np-CuTi, transmission electron microscopy (TEM) characterization was performed on a cross-sectioned specimen prepared using a focused ion beam (FIB) technique. High-angle annular dark-field (HAADF)-TEM image again confirmed the bimodal porous nature of np-CuTi (Fig. 3b). The high-magnification image, Fig. 3c, clearly shows that the material ligaments and nanopores are similar in size (ca 15 nm), in good agreement with the grain size estimated from PXRD data using the Scherrer’s method (Supplementary Table 2) and the pore size observed in N2 adsorption-desorption analysis (Supplementary Fig. 4). The np-CuTi catalyst was also examined using electron energy loss spectroscopy (EELS). Although Fig. 3d shows the contrast image of a selected region for spectroscopic evaluation, Fig. 3e,f shows the associated Cu and Ti EELS mappings using the L2,3 edge of Cu and Ti, respectively. It is evident that Cu and Ti atoms are homogeneously distributed along the material ligaments, consistent with the conclusion of a solid solution from the PXRD results. Moreover, near-edge fine structure analysis confirmed the metallic nature of Cu and Ti. No oxygen K-edge signal was detected in the EELS spectra. High-resolution TEM image exhibits uniform lattice fringes (Fig. 3g), further confirming the highly crystalline nature of np-CuTi.


Highly porous non-precious bimetallic electrocatalysts for efficient hydrogen evolution.

Lu Q, Hutchings GS, Yu W, Zhou Y, Forest RV, Tao R, Rosen J, Yonemoto BT, Cao Z, Zheng H, Xiao JQ, Jiao F, Chen JG - Nat Commun (2015)

XRD and TEM characterization.(a) The XRD patterns of np-CuTi and Ti-free np-Cu. Inset: the enlarged region of Cu (111) diffraction peaks, with the dotted line indicating the peak position of pure Cu. (b) High-angle annular dark-field (HAADF) scanning (S)TEM image of a cross-sectioned np-CuTi sample prepared using FIB technique. Scale bar, 1 μm. (c), HAADF STEM image with a higher magnification. The box indicates the region selected for EELS study. Scale bar, 50 nm. (d–f) The contrast image of the selected region for EELS mapping study and its corresponding Cu (e) and Ti (f) maps. Scale bar, 50 nm. (g) High-resolution TEM image with visible lattice fringes. Inset: The Fourier transform confirms that np-CuTi is composed of an extended crystalline network. Scale bar, 2 nm.
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f3: XRD and TEM characterization.(a) The XRD patterns of np-CuTi and Ti-free np-Cu. Inset: the enlarged region of Cu (111) diffraction peaks, with the dotted line indicating the peak position of pure Cu. (b) High-angle annular dark-field (HAADF) scanning (S)TEM image of a cross-sectioned np-CuTi sample prepared using FIB technique. Scale bar, 1 μm. (c), HAADF STEM image with a higher magnification. The box indicates the region selected for EELS study. Scale bar, 50 nm. (d–f) The contrast image of the selected region for EELS mapping study and its corresponding Cu (e) and Ti (f) maps. Scale bar, 50 nm. (g) High-resolution TEM image with visible lattice fringes. Inset: The Fourier transform confirms that np-CuTi is composed of an extended crystalline network. Scale bar, 2 nm.
Mentions: The PXRD data for np-CuTi (Fig. 3a) suggested a similar crystal structure with that of the bulk Cu-Ti alloys. A small unit cell expansion (Supplementary Table 2) was also observed because ofTi substitution. The atomic ratio of Ti to (Cu+Ti) of np-CuTi was verified to be about 5 at. % by EDX analysis (Supplementary Fig. 5), mimicking the optimal composition of Cu95Ti5 from the bulk Cu-Ti alloy study. The consistency in their surface conditions was also confirmed using XPS characterizations (Supplementary Fig. 6). To further study the structure of np-CuTi, transmission electron microscopy (TEM) characterization was performed on a cross-sectioned specimen prepared using a focused ion beam (FIB) technique. High-angle annular dark-field (HAADF)-TEM image again confirmed the bimodal porous nature of np-CuTi (Fig. 3b). The high-magnification image, Fig. 3c, clearly shows that the material ligaments and nanopores are similar in size (ca 15 nm), in good agreement with the grain size estimated from PXRD data using the Scherrer’s method (Supplementary Table 2) and the pore size observed in N2 adsorption-desorption analysis (Supplementary Fig. 4). The np-CuTi catalyst was also examined using electron energy loss spectroscopy (EELS). Although Fig. 3d shows the contrast image of a selected region for spectroscopic evaluation, Fig. 3e,f shows the associated Cu and Ti EELS mappings using the L2,3 edge of Cu and Ti, respectively. It is evident that Cu and Ti atoms are homogeneously distributed along the material ligaments, consistent with the conclusion of a solid solution from the PXRD results. Moreover, near-edge fine structure analysis confirmed the metallic nature of Cu and Ti. No oxygen K-edge signal was detected in the EELS spectra. High-resolution TEM image exhibits uniform lattice fringes (Fig. 3g), further confirming the highly crystalline nature of np-CuTi.

Bottom Line: Although both copper and titanium are known to be poor hydrogen evolution catalysts, the combination of these two elements creates unique copper-copper-titanium hollow sites, which have a hydrogen-binding energy very similar to that of platinum, resulting in an exceptional hydrogen evolution activity.In addition, the hierarchical porosity of the nanoporous copper-titanium catalyst also contributes to its high hydrogen evolution activity, because it provides a large-surface area for electrocatalytic hydrogen evolution, and improves the mass transport properties.Moreover, the catalyst is self-supported, eliminating the overpotential associated with the catalyst/support interface.

View Article: PubMed Central - PubMed

Affiliation: 1] Center for Catalytic Science and Technology, Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, USA [2] Department of Chemical Engineering, Columbia University, New York, New York 10027, USA.

ABSTRACT
A robust and efficient non-precious metal catalyst for hydrogen evolution reaction is one of the key components for carbon dioxide-free hydrogen production. Here we report that a hierarchical nanoporous copper-titanium bimetallic electrocatalyst is able to produce hydrogen from water under a mild overpotential at more than twice the rate of state-of-the-art carbon-supported platinum catalyst. Although both copper and titanium are known to be poor hydrogen evolution catalysts, the combination of these two elements creates unique copper-copper-titanium hollow sites, which have a hydrogen-binding energy very similar to that of platinum, resulting in an exceptional hydrogen evolution activity. In addition, the hierarchical porosity of the nanoporous copper-titanium catalyst also contributes to its high hydrogen evolution activity, because it provides a large-surface area for electrocatalytic hydrogen evolution, and improves the mass transport properties. Moreover, the catalyst is self-supported, eliminating the overpotential associated with the catalyst/support interface.

No MeSH data available.