Stably suspended SiO2-supported CdS photocatalyst for a promising organic pollutant degradation in the absence of mechanical stirring.

Even with solar-activatable photocatalyst, incommensurable energy input for stirring is still required to overcome the transport limitations in powder-photocatalysis. To counter this, a novel concept of auto-suspending photocatalyst based on SiO2/CdS was proposed to enable promising photo-activity even under stirring-free condition. Functionally-speaking, CdS would act as photoreaction-driver while SiO2 endows sufficient buoyance for suspension-stabilization during stirring-free photocatalysis. In photoreactions degrading methylene blue for theoretical demonstration, SiO2/CdS_0.3 promises only 4.57% activity reduction in non-stirred photoreaction, enabling 15.26% of methylene blue decolorization comparing to 15.99% of stirred-photoreaction under visible light irradiation. This could be ascribed to the slow settling tendency of SiO2/CdS_0.3, evading severe light-shielding under stacked condition. Also, its rightly-exposed SiO2 surface permits 'adsorb-and-degrade' mechanism, thereby overcoming the sluggish surface transport across thick boundary layer. Contrarily, photocatalyst with quintuple CdS content (SiO2/CdS_1.5) exhibits largest activity reduction (31.47%), reasoned by its quick-settling tendency. Overall, current study provides new perspectives to photocatalysis-community. The success elimination of mechanical stirring from photocatalysis promises significant energy-saving (19.1-136 kW/m3), thus consenting better practicality for solar energy-harvesting and environmental protection.