Sulfur quantum dots integration in conductive microrod array enable superior oxygen evolution performance

Exploring highly efficient and low-cost electrocatalysts for the oxygen evolution reaction (OER) is highly desirable but remains a great challenge for the development of renewable energy conversion and storage systems. Though the earth-abundant cobalt-based catalysts have shown great promise as efficient OER electrocatalyst candidates due to their unique 3d electron number and special atomic orbitals. However, the adsorption/desorption of oxygenous intermediates on the pristine Co sites is suboptimal, and further electronic modulation is still required. Thus, developing a reliable strategy to optimize the activity of Co sites is crucial for enhancing electrocatalytic performance and still needs further elaborate elucidation. Here, sulfur dots mediator were used as electron donors to construct electron-rich Co sites in cobalt-based catalyst, which facilitates the mutual electron interaction between Co sites and oxygen intermediate. The negative charges are easier to accumulate on three anti-bonding orbitals of Co sites, resulting in downshifted d-band centers and reduces the free energy barrier of the potential-determining step, promoting the desorption of oxygen intermediates, as evidenced using density functional theory calculations. Thus, an sulfur dots-assisted strategy is proposed to endow the Co sites with modulated electron structures in Co(TCNQ)₂ (7,7,8,8-tetracyanoquinodimethane: TCNQ). The formation of electron-accumulation Co^δ- thereby increases the antibonding-orbital occupancy of Co-O_ads, subsequently promoting the desorption of *OOH. The optimal catalyst delivers impressive OER performance, achieving a sharp decrease in overpotential from 390 mV to 238 mV to attain current density of 10 mA cm^-2 in 1.0 M KOH and a lower Tafel slope of 55.2 mV dec^-1 in comparison with the regular catalyst RuO₂/CF. In general, this work offers insights into regulating electronic structure of Co sites via introducing an electron donor, which in turn contributes to the design of high-performance electrocatalysts for OER in water splitting.