Cobalt-based nanomaterials have been intensively explored as one of the most promising noble-metal-free oxygen evolution reaction (OER) electrocatalysts. However, most of their performances are still inferior to state...Cobalt-based nanomaterials have been intensively explored as one of the most promising noble-metal-free oxygen evolution reaction (OER) electrocatalysts. However, most of their performances are still inferior to state-of-the-art precious metals especially for Ru and Ir.Herein, we apply a continuous ion exchange method and further hydrothermal treatment to synthesize the flake-like Ag-CoSO4 nanohybrids beginning from Co-BTC (BTC:benzene-1,3,5-tricarboxylic acid) metal-organic frameworks precursor. The catalyst exhibits superior OER performance under the alkaline electrolyte solution (a low overpotential of 282 mV at 10 mA/cm2 in 1 mol/L KOH), which is even better than RuO2 due to the improved conductivity and rapid electrons transfer process via introducing small amount of Ag. The existence of Ag in the hybrids is beneficial for increasing the Co(IV) concentration, thus promoting the *OOH intermediate formation process. Besides, due to the very low requirement of Ag content (lower than 1 atom%), the cost of the catalyst is also limited. This work provides a new insight for designing of inexpensive OER catalysts with high performance and low cost.展开更多
We investigate the threading dislocation(TD)density in N-polar and Ga-polar GaN films grown on sapphire substrates by metal-organic chemical vapor deposition.X-ray diffraction results reveal that the proportion of scr...We investigate the threading dislocation(TD)density in N-polar and Ga-polar GaN films grown on sapphire substrates by metal-organic chemical vapor deposition.X-ray diffraction results reveal that the proportion of screw type TDs in N-polar GaN is much larger and the proportion of edge type TDs is much smaller than that in Ga-polar.Transmission electron microscope results show that the interface between the AlN nucleation layer and the GaN layer in N-polar films is smoother than that in Ga-polar films,which suggests different growth modes of GaN.This observation explains the encountered difference in screw and edge TD density.A model is proposed to explain this phenomenon.展开更多
基金supported by the National Natural Science Foundation(No.21271163,No.1232211,No.21571168)the Fundamental Research Funds for the Central Universities(WK2060140021)the CAS/SAFEA International Partnership Program for Creative Research Teams and the Hefei Science Center CAS(2016HSC-IU011)
文摘Cobalt-based nanomaterials have been intensively explored as one of the most promising noble-metal-free oxygen evolution reaction (OER) electrocatalysts. However, most of their performances are still inferior to state-of-the-art precious metals especially for Ru and Ir.Herein, we apply a continuous ion exchange method and further hydrothermal treatment to synthesize the flake-like Ag-CoSO4 nanohybrids beginning from Co-BTC (BTC:benzene-1,3,5-tricarboxylic acid) metal-organic frameworks precursor. The catalyst exhibits superior OER performance under the alkaline electrolyte solution (a low overpotential of 282 mV at 10 mA/cm2 in 1 mol/L KOH), which is even better than RuO2 due to the improved conductivity and rapid electrons transfer process via introducing small amount of Ag. The existence of Ag in the hybrids is beneficial for increasing the Co(IV) concentration, thus promoting the *OOH intermediate formation process. Besides, due to the very low requirement of Ag content (lower than 1 atom%), the cost of the catalyst is also limited. This work provides a new insight for designing of inexpensive OER catalysts with high performance and low cost.
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFB0400100the China Postdoctoral Science Foundation under Grant No 2015M582610
文摘We investigate the threading dislocation(TD)density in N-polar and Ga-polar GaN films grown on sapphire substrates by metal-organic chemical vapor deposition.X-ray diffraction results reveal that the proportion of screw type TDs in N-polar GaN is much larger and the proportion of edge type TDs is much smaller than that in Ga-polar.Transmission electron microscope results show that the interface between the AlN nucleation layer and the GaN layer in N-polar films is smoother than that in Ga-polar films,which suggests different growth modes of GaN.This observation explains the encountered difference in screw and edge TD density.A model is proposed to explain this phenomenon.
