RESUMEN
CeO2 nanocubes with average sizes of 9, 13, and 18 nm have been synthesized by preparing a slightly basic aqueous mixture of Ce(NO3)3, Na2SO4, and NH4OH and heating the solution to 100 to 150 °C in 4 or 9 h. The nanocubes possess high crystalline quality. Their band gaps decrease gradually beyond the quantum confinement regime from 3.57 eV to 3.45 eV with increasing particle sizes. The 9 nm CeO2 nanocubes have the most positive valence band energy and correspondingly they exhibit the best electrochemical oxygen evolution reaction activity. Since band gaps of semiconductor nanocrystals can be tuned substantially through particle size control to yield different band energies, this fact can be utilized to enhance the electrochemical and photocatalytic properties.
RESUMEN
As a source of clean and sustainable energy, reliable hydrogen production requires highly efficient and stable electrocatalysts. In recent years, molybdenum disulfide (MoS2) has been demonstrated as a promising electrocatalyst for hydrogen evolution reactions (HERs). Here, we demonstrate that a three-dimensional (3D) MoS2 quantum dot (MoS2QD) aerogel is an efficient cathode electrocatalyst that can be used to enhance the HER in acid, neutral, and alkaline (e.g., real seawater) environments. In studying the effects of the exfoliated MoS2 dimension for the HER, we found that the biofunctionalized exfoliated MoS2QD shows much higher cathodic density, a more lower energy input, and a lower Tafel slope for the HER than the larger size of the chlorophyll-assisted exfoliated MoS2, highlighting the importance of the size of the MoS2 aerogel support for accelerating the HER performance. Moreover, the electrocatalytic activity of MoS2QD-aerogel is superior to that of Pt in neutral conditions. In real seawater, the MoS2QD-aerogel sample exhibits stable HER performance after consecutive scanning for 150 cycles, while the HER activity of the Pt dramatically decreases after 50 cycles. These results showed for the first time how the 3D MoS2 configuration in MoS2 aerogel can be used to effectively produce hydrogen for clean energy applications.
