Synthesis of CaMn₂O₄-related electrocatalyst for oxygen evolution electrode of water-splitting

Abstract

Water-splitting by using electric power produced by solar cells is promising system to produce hydrogen without fossil fuels. Oxygen evolving catalyst is, however, major problem to prevent using this system widely because precious materials are used in the catalyst. Considering from the photosynthesis II of plants, the compound of Ca-Mn-O is one of the candidates for the oxygen evolving catalyst. In this study, the synthesis condition and the oxygen evolving electrocatalytic activity of CaMn2O4•xH2O are investigated. The overpotential at 0.1 mA/cm2 was 0.28 V when using the electrode of carbon paste and CaMn2O4•H2O with the weight ratio of 3:1.

Hydrothermal Synthesis of CaMn2O4·xH2O Nanorods as Co‐Catalysts on GaN Nanowire Photoanode

“…The observed activity trends possibly arise from optimized dimensions of the nanorods synthesized at 210 °C. It could also be attributed to the instability of the Mn(3) ions in the rigid and highly symmetric MnO 6 octahedron, which can decrease the activity of CaMn 2 O 4 ·xH 2 O under neutral pH 30 . The presence of Mn(3) ions was confirmed by XPS analysis, as shown in Figure S1.…”

“…Therefore, the development of alternative inexpensive, highly active and widely available co‐catalysts is crucial 26–28 . Inspired by the natural photosynthetic system, manganese oxides and Mn‐based composite oxides have attracted significant attention as nonprecious metal electrocatalysts due to low costs of manganese and the envisioned biomimetic character 29–33 . Natural photosynthetic system is catalyzed by the μ‐oxido‐Mn 2 Ca cluster of the oxygen evolving complex (OEC) and its unique ligand environment for photosystem II 34 .…”