Dumbbell Defect Containing Chromium-Rich Lithium-Vacant Layered Li_yCr_1–xFe_xO₂(y≤ 1, 0 ≤x≤ 0.2): An Unexplored and Highly Efficient Electrocatalyst for the Oxygen Evolution Reaction

Oxygen electrochemistry plays a critical role in water electrolysis, fuel cells, and metal–air batteries as efficient energy storage and conversion technology to harness renewable energies. Dumbbell defects containing chromium-rich lithium-vacant layered structure LiCrO 2 are envisaged here as an efficient oxygen evolution reaction (OER) electrocatalyst due to the presence of Cr 6+ ions at interstitial sites that facilitates −Cr–O–OH formation in basic media. The presence of Cr 6+ ions at the dumbbell interstitial sites of the hexagonal close-packed LiCrO 2 lattice was confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy studies. The crystal structure, morphology, and composition of the materials were confirmed by powder X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and inductively coupled plasma–mass spectrometry analysis. Rhombohedral structure formation and formation of Cr 6+ ion interstitials in the Li layer increase that varies with Fe doping in Li y Cr 1– x Fe x O 2 ( y ≤ 1, 0 ≤ x ≤ 0.2), and the best OER activity is achieved for Li 0.6 Cr 0.9 Fe 0.1 O 2 (LCFO-10) with a Tafel slope of 50 mV dec –1 and an overpotential of 311 mV at a current density of 10 mA cm –2, better than that of the RuO 2 (overpotential ∼336 mV) benchmark catalyst. At an overpotential of 350 mV, the OER current density of LCFO-10 is 28.07 mA cm –2, which is ∼2 times higher than the OER current density observed with commercial RuO 2 (13.22 mA cm –2 ), indicating its superior electrocatalytic performances. The remarkable enhancement of OER performance may be attributed to the synergistic interaction of Cr 6+ and Fe 3+ ions present in the lattice.