Catalytically Active Cr ₂ O ₃ -Decorated Spinel MnCo ₂ O ₄ Nanobelt for Bifunctional Electrocatalytic Water Splitting Reaction

Electrocatalytic water splitting using nonprecious metal-based catalysts is significantly important for clean energy production and storage sectors. The existence of Mn and Co metals in the spinel MnCo 2 O 4 structure may influence the electrocatalytic performance synergistically; hence, incorporating it with additional active species can further enhance the catalytic activity. Here, Cr 2 O 3 nanoparticles are used to decorate the surface of a MnCo 2 O 4 nanobelt, in which Cr 2 O 3 acts as an active site for the electrocatalytic reactions. The Cr 2 O 3 nanoparticles can be strategically distributed on the surface of the MnCo 2 O 4 nanobelt, developing a highly efficient catalyst system. The Cr 2 O 3 -decorated MnCo 2 O 4 electrocatalyst requires low overpotentials of 213 and 144 mV to achieve 10 mA cm –2 for OER and HER, respectively, facilitating faster electron transfer kinetics, and its enhanced performance may be attributed to two reasons. First, the Cr 2 O 3 nanoparticles increase the surface area of the catalyst, providing more active sites, which leads to improved electrocatalytic efficiency and enhanced kinetics. Second, introducing Cr 2 O 3 alters the electronic structure and surface properties of MnCo 2 O 4, resulting in modified reaction pathways and reduced energy barriers for water-splitting reactions, which are confirmed by theoretical calculations. Furthermore, the Cr 2 O 3 -decorated MnCo 2 O 4 nanobelt exhibits good stability and durability, making it suitable for long-term water-splitting applications. The turnover frequency (TOF) of Cr 2 O 3 /MnCo 2 O 4 was calculated to be 5.79 × 10 –2 s –1 . The synergistic combination of MnCo 2 O 4 and Cr 2 O 3 results in a bifunctional catalyst that can efficiently facilitate oxygen and hydrogen evolution reactions, making it a promising candidate for overall water splitting.