Morphology and Phase Evolution of CoAl Layered Double Hydroxides in an Alkaline Environment with Enhanced Pseudocapacitive Performance

Abstract

The morphology and phase transformation of CoAl layered double hydroxide (denoted CAL) nanoplates are systematically investigated in highly concentrated basic solution. Characterization results reveal that this is a time‐dependent process, in which CALs are gradually converted to β‐Co(OH)2 and CoOOH, and the structure becomes increasingly porous. This process could be caused by the dissolution of the Al part of CoAl LDHs, recrystallization of the Co part, and subsequent oxidation of Co. It is found that the pseudocapacitive performance of the products vary with the immersion time. CALs already show a reasonable performance, whereas short‐term treatment would lead to the enhanced capacitance of 1123 F g−1 with both remarkable rate capability and stability. However, the formation of CoOOH will significantly degrade the supercapacitive performance.

Hierarchical Co-based Porous Layered Double Hydroxide Arrays Derived via Alkali Etching for High-performance Supercapacitors

“…XRD data of Co(OH) 2 @PLDH and Co(OH) 2 @CoAl LDH showed a series of similar Bragg reflections (XRD pattern for Co(OH) 2 NS was also shown in Figure S1 for comparison). In XRD pattern of Co(OH) 2 @CoAl LDH, the peaks marked ‘#’ were in good agreement with the well-known LDH Co 6 Al 2 CO 3 (OH) 16 •H 2 O (JCPDF: 51-0045) with the characteristic peaks of (003) and (006) planes, which revealed an interlayer distance of 0.74 nm, indicating the occupying of CO 3 2− ions and water molecules in the interlayer spaces 37 . While the peaks marked ‘*’ referred to the primary Co(OH) 2 (JCPDF: 45-0031), and no reflections due to crystalline impurities was observed (the peaks marked ‘&’ donate the Ni substrate).…”

Chemical Modifications of Layered Double Hydroxides in the Supercapacitor

“…The increased specific capacitance of the MPCCH is due to the increased active sites of CoAl LDH after the deprecation of Al. Xu et al [ 80 ] studied the effect of etching time on the pseudocapacitive performance of CoAl LDH (Figure 8d–f). The alkali etching of CoAl LDH was calculated for 0, 1, 2, 4, 6, 12, 48, and 72 h, respectively.…”

“…d) The crystal phase transition of CoAl LDH with the increase of alkali etching time, e and f) the XRD patterns of CoAl LDH with different etching time. [ 80 ] Copyright 2015, John Wiley & Sons, Inc. g) The preparation schematic of CoMoAl LDH derivate phosphides, h) the SEM images, and i) TEM images of CoMoAl LDH derivate phosphides. [ 82 ] Copyright 2019, American Chemical Society.…”

Molybdenum-Doped Porous Cobalt Phosphide Nanosheets for Efficient Alkaline Hydrogen Evolution

“…But the atomic ratio of Al to M (M = Co, Mo) in the electrocatalyst decreased from the initial value of 14.9% (CoMo­(Al)-P) to 1.4% ( p CoMo-P). Accordingly, the dissolution of the Al species plays a critical role in modifying the morphology and further boosting the electrocatalytic HER activity of CoMo­(Al)-P/NF during a dynamical reaction. − Additionally, the CoMo-P nanosheets, with no Al species added in its hydroxide precursors, did not exhibit porous structure or activity increase during the CV cycling test (Figure S13).…”