Photoirradiation-Induced Exposure of Active Sites on Co ₃ (Si ₂ O ₅ ) ₂ (OH) ₂ Nanosheets for Enhanced Electrocatalytic Oxygen Evolution Reaction

Electrocatalytic water splitting, as a highly promising hydrogen production technology, hinges critically on the oxygen evolution reaction (OER). Serpentine structured materials are inexpensive, chemically stable, and electrochemically active in OER. However, the OER activity of these materials remain limited due to the scarcity of active sites. Here, a series of serpentine Co 3 (Si 2 O 5 ) 2 (OH) 2 catalyst materials are synthesized via hydrothermal synthesis and photo irradiation treatment. All synthesized catalysts retained a consistent layered nanosheet structure. The photo irradiated Co 3 (Si 2 O 5 ) 2 (OH) 2 catalysts exhibited excellent OER performance, with the Co 3 (Si 2 O 5 ) 2 (OH) 2 irradiated for 12 h displaying the highest OER activity. Electrochemical testing confirmed that photo irradiation enhanced the electrochemical active area of the catalyst material while reducing charge transfer resistance, thereby facilitating charge transfer during the OER process. Concurrently, Co 3 (Si 2 O 5 ) 2 (OH) 2 irradiated for 12 h demonstrated outstanding stability, maintaining a stable voltage for 85 h at 10 mA cm –2 . Theoretical calculations further reveal that photoirradiation modulates the electronic structure of Co sites, shifting the d-band center closer to the Fermi level and thereby strengthening the adsorption of OER intermediates while lowering the reaction energy barrier. The solar driven water splitting process achieves a high Faradaic efficiency of 93.83%, and the solar-to-hydrogen energy conversion efficiency is 4.66%. This work provides an effective strategy for designing inexpensive and stable OER electrocatalysts.