Abstract
CuMn2O4 and Cu1.5Mn1.5O4 mixed-metal copper-manganese oxide spinels were synthesized via a hydrothermal route to investigate the influence of composition and morphology on bifunctional electrocatalysis for alkaline water splitting. Structural and microscopic analyses revealed that CuMn2O4 forms a hierarchical spear-like architecture, whereas Cu1.5Mn1.5O4 develops plate-like assemblies. Owing to its open, porous nanosheet network and abundant surface-exposed Mn active sites, CuMn2O4 delivers markedly enhanced catalytic performance, requiring overpotentials of only 290 mV for the oxygen evolution reaction (OER) and 17 mV for the hydrogen evolution reaction (HER) at 10 mA·cm−2. It also exhibits small Tafel slopes of 98.2 mV·dec−1 (OER) and 59.1 mV·dec−1 (HER), along with excellent durability over extended chronoamperometric operation (10 h for OER and 16 h for HER). The superior activity is further supported by a large electrochemically active surface area (27.31 mF·cm−2), attributed to the hierarchical porous structure that facilitates charge transfer and mass transport. These results highlight CuMn2O4 as a promising, earth-abundant bifunctional catalyst for efficient alkaline water splitting.