BARC/PUB/2019/0754

 
 

High oxygen evolution reaction activity on lithiated nickel oxides - Activity descriptors

 
     
 
Author(s)

Sankannavar, R.; Sandeep, K. C.; Kamath, S.; and others
(HWD)

Source

Electrochimica Acta, 2019. Vol. 318: pp. 809-819

ABSTRACT

Alkaline water electrolyzers promise very high purity hydrogen gas production but suffer from large overpotential for anodic oxygen evolution reaction (OER). Here we describe the effect of lithium (Li+)-substitution into nickel oxide on the electrocatalytic activity towards OER in alkaline electrolyte. The Xray diffraction patterns of lithiated nickel oxides (LixNi1-xO, x = 0.00-0.50) synthesized by the solutioncombustion method suggest that pure phase of lithiated nickel oxide was formed until x = 0.30; thereafter, a secondary phase of LiNiO2 was observed. Rietveld analysis showed that Li+-substitution caused a contraction in the lattice structure as shown by the decrease in lattice parameters upon Li+-substitution. Further, the weight fraction of LiNiO2 was found to be dominant for x = 0.50. Deconvolution of the high resolution X-ray photoelectron spectroscopy for O 1s and Ni 2p spectra suggested that concentration of oxygen vacancies increased linearly, whereas that of Ni3+ increased till x = 0.30 and it decreased when Li+-substitution was further increased to x = 0.40 and 0.50. Although electrical conductivity increased upon Liþ-substitution, no significant effect was observed for lithiated samples with varying Li+-content (x = 0.10-0.50). The activities for OER were measured using the rotating disk electrode in 0.5M NaOH electrolyte, and the data suggest that lithiated nickel oxide synthesized with x = 0.30 shows the highest current density at 1.70 vs. RHE (V). The decrease in OER activity for x = 0.40 and 0.50 was attributed to the decline in OER active Ni3+ sites (probably due to the presence of chemically unstable LiNiO2).

 
 
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