Perovskite CoSn(OH)₆ nanocubes with tuned d-band states towards enhanced oxygen evolution reactions

The CoSn(OH)₆ perovskite hydroxide is a structure stable and inexpensive electrocatalyst for the oxygen evolution reaction (OER). However, the OER activity of CoSn(OH)₆ is still unfavorable due to its limited active sites. In this work, an Fe³⁺ doping strategy is used to optimize the d-band state of the CoSn(OH)₆ perovskite hydroxide. The CoSn(OH)₆ catalyst with slightly Fe³⁺ doped nanocubes is synthesized by a facile hydrothermal method. Structure characterization shows that Fe³⁺ ions are incorporated into the crystal structure of CoSn(OH)₆. Owing to the regulation of the electronic structure, CoSn(OH)₆-Fe1.8% exhibits an OER overpotential of 289 mV at a current density of 10 mA cm^-2 in OER electrochemical tests. In situ Raman spectroscopy shows that no obvious re-construction occurred during the OER for both CoSn(OH)₆ and CoSn(OH)₆-Fe1.8%. DFT calculations show that the introduction of Fe³⁺ into CoSn(OH)₆ can shift the d-band center to a relatively high position, thus promoting the OER intermediates' adsorption ability. Further DFT calculations suggest that incorporation of an appropriate amount of Fe³⁺ into CoSn(OH)₆ significantly reduces the rate-determining Gibbs free energy during the OER. This work offers valuable insights into tuning the d-band center of perovskite hydroxide materials for efficient OER applications.