NOVELTY - Ammonium salt, cadmium salt, thiourea, and water are reacted to obtain yellow cadium sulfide solid pressed powder (I). Powder (I) is washed with deionized water and filtered to obtain pressed powder (II). Powder (II) is roasted and ground to obtain solid powder (III). Cobalt salt, aqueous ammonia, and water are reacted to obtain cobaltammine complex-ion solution. Solid powder (III) is dispersed. The obtained material is thermally processed, roasted and ground, to obtain a p-cobalt oxide/n-cadmium sulfide composite semiconductor photocatalyst.    USE - Preparation of p-cobalt oxide/n-cadmium selenide composite semiconductor photocatalyst used for decomposing organic pollutants, for decomposing water to produce hydrogen, and producing solar battery.    DETAILED DESCRIPTION - (In wt.%) ammonium salt (0.001-90), cadmium salt (0.001-70), thiourea (0.001-90), and deionized water (0.001-90) are mixed and pre-reacted for 0.1-10 hours in a microwave reactor at 30 W to 15 KW. The mixture is then reacted for 0.1-30 hours at 0-160 degrees C under ultrasound dispersion at 20 KHz to 1 MHz and 30 W to 15 KW. The reaction product is filtered to obtain yellow calcium selenide solid pressed powder (I). Deionized water (1-10 times the weight of pressed powder) is added to the pressed powder and the powder is washed, followed by ultrasound dispersion for 0.1-5 hours and filtration. These operations are repeated thrice to obtain cadmium sulfide solid pressed powder (II). The pressed powder is roasted for 0.1-10 hours at 200-250 degrees C under nitrogen protection, then for 0.1-10 hours at 300-350 degrees C, and then for 0.1-10 hours at 400-480 degrees C to obtain cadmium sulfide solid powder (III) after cooling and grinding. Cobalt salt (0.001-70), aqueous ammonia (0.001-90), and deionized water (0.001-90) are mixed and reacted, to obtain a cobaltammine complex-ion solution. Solid powder (III) (0.001-90) is added, stirred into a suspension, and dispersed for 0.1-10 hours by ultrasonic wave disperser at 20 KHz to 1 MHz and 30 W to 15 KW. Reduced-pressure distillation is carried out at 50-100 degrees C to remove water and volatile ammonia. The obtained material is thermally processed for 1-10 hours at 150-300 degrees C under nitrogen protection. The material is cooled, added to deionized water for washing, ultrasound-dispersed for 0.1-5 hours, and filtered. Washing, dispersion and filtration are repeated thrice, to obtain solid powder (IV). Solid powder (IV), under nitrogen protection, is roasted for 0.1-10 hours at 200-250 degrees C, then for 0.1-10 hours at 300-350 degrees C, and then roasted for 0.1-10 hours at 550-600 degrees C to obtain solid powder (V). Solid powder (V) is cooled and ground to obtain a p-cobalt oxide/n-cadmium sulfide composite semiconductor photocatalyst.