Designing CdS Based Photocatalysts For Solar Hydrogen Generation

Nowadays,the rapid development of industrialization and urbanization leads to the shortage of global energy resources,and the effluent discharge for the large amount of toxic and harmful chemical pollutants around our environment.Therefore,a new and green technology is urgently needed to develop for solution of the aforementioned energy and environmental crises.In recent years,the conversion of solar energy into chemical fuel based on semiconductors using the photocatalytic technology has been widely studied.Notably,Cadmium sulfide(CdS)has attracted extensive attention due to its relatively narrow bandgap and sufficiently negative conduction band,which are capable of sunlight absorption and proton reduction.However,the low efficient separation of the photogenerated carriers severely limits its practical applications.We adopt the surface conjugation self-assembly strategies to respectively optimize the dynamics of photogenerated electron and hole in CdS,leading to the increases in charge separation efficiency and reactivity.These strategies obviously improve the photocatalytic performance,sheding new light on the design of solar photocatalytic systems.The strategies are specifically described as follows:1.Combining photoharvesting semiconductors with co-catalysts is an intriguing approach to develop inexpensive and efficient photocatalysts,however,how to coordinate light absorbers and catalytic sites still remains a great challenge.Here,we propose a facile strategy for optimizing assembly of CdS-MoS2(CM)nanohybrids with controlled active edge exposure by cation coordination competition in one-pot solvothermal synthesis.With the involvement of Cd ions,more formed CdS nanocrystals coordinated preferentially with MoS2 edges self-optimize into unique CM hybrids,which enables the maximum performances of active area and photo-induced electron transfer and injection into the photocatalytic H2 evolution reaction(HER).As a result,the optimum CM hybrids exhibit an outstanding and stable photocatalytic activity with a H2 evolution rate of up to 1009 mmol h-1 g-1,more than 104-fold higher than that of pure CdS,which is the best among the state-of-the-art heterogeneous photocatalysts.This work provides a facile strategy for a controlled configuration of MoS2 edge active sites on photoharvesting semiconductors toward high-efficiency solar photocatalytic H2 generation.2.Solar water splitting to H2 fuel is considered as a sustainable approach to meet green energy demands in the future,but is mainly limited owing to the sluggish hole dynamics involved in the water oxidation reaction and bulk charge separation.Herein,we implemented hole dynamics engineering over CdS nanoparticles(NPs)via the oxidation reaction substitution with a facile urea oxidation reaction(UOR)and surface conjugation with sulfurous groups(-S/SOx2-)as hole-extraction chains,which thermodynamically reduced the reaction barrier and kinetically accelerated the charge separation concomitantly.We then demonstrated a highly efficient photocatalytic H2 evolution from a urea solution with valuable urea degradation.An impressive and stable H2 generation rate of 1.49 mmol h-1 g-1 was achieved under 1 sun irradiation with an apparent quantum yield(AQY)of up to 2.4%at 420 nm.In this study,we designed CdSxO NP photocatalysts to enable hole thermodynamic and kinetic acceleration,which promise a cost-effective and course-smooth solar H2 production along with urea-rich wastewater purification.