Mn2+-doped Co3Si2O5(OH)4 serpentine nanosheets with tuned d-band centers for efficient oxygen evolution in alkaline and neutral electrolytes

Abstract

Serpentine structured Co₃Si₂O₅(OH)₄ is inexpensive, chemically stable, and electrochemically active in oxygen evolution reactions (OER). However, the OER activity of Co₃Si₂O₅(OH)₄ materials is still unfavorable due to the low active sites. Here, Mn²⁺-doped Co₃Si₂O₅(OH)₄ serpentine nanosheets with tuned d-band centers are achieved for efficient oxygen evolution in alkaline and neutral electrolytes. The Co_xMn_3−xSi₂O₅(OH)₄ serpentine nanosheets are synthesized by a simple hydrothermal method. The optimized Co_2.4Mn_0.6Si₂O₅(OH)₄ serpentine nanosheets showed favorable OER overpotentials as well as stable durability in KOH solution and phosphate buffer solution, which were superior to most of the Co-based and Mn-based OER electrocatalysts. The in situ Raman spectroscopy shows that the materials are kept well in the electrochemical OER environments. Further density functional theory shows that the d-band center of Co_xMn_3−xSi₂O₅(OH)₄ serpentine nanosheets is shifted more upward in comparison with pristine Co₃Si₂O₅(OH)₄. The changes in the d-band center increase the adsorption of intermediates, optimize the reaction steps, and lower the energy barriers of the OER. That is the main reason for the OER enhancement Mn²⁺-doped Co₃Si₂O₅(OH)₄. This work gives an efficient strategy to design cheap and stable electrocatalytic materials for OER in a broad pH environment.

Graphical abstract