Utilizing the built-in electric field of p-n heterojunction to spatially separate the photogenerated charges in C, N co-doped Co3O4/CdS photocatalysts

• CN-CoO/CdS p-n type heterojunctions are formed using C, N co-doped Co 3 O 4 and CdS. • CN-CoO/CdS has higher visible light absorption, faster charge separation and excellent photoelectrochemical performance. • The outstanding photocatalytic performance of CN-CoO/CdS is mainly attributed to its built-in electric field. • The photocatalytic hydrogen evolution rate of the optimal 15%CN-CoO/CdS reaches 64.36 mmol·g −1 ·h −1 under visible light. • The 15%CN-CoO/CdS exhibits excellent stability during the photocatalytic cycle for hydrogen evolution reaction with 30 h. As one of the most effective strategies for the storage and utilization of solar energy, the development of photocatalytic technology has received extensive attention. The core work, the design and modification of photocatalysts, is very significance. Herein, we prepared C, N co-doped Co 3 O 4 (CN-CoO) by a simple method and composited it with CdS to form CN-CoO/CdS p-n type heterojunctions. The prepared materials are characterized by numerous tests, such as XRD, SEM, TEM, XPS, and photoelectrochemical measurement. Due to the excellent electrochemical performance of CN-CoO and the built-in electric field in CN-CoO/CdS, the efficient separation of photogenerated charges is realized. Compared with CdS (1.11 ns), the average carrier lifetimes of the 15%CN-CoO/CdS (1.63 ns) is prolonged, which enhances photocatalytic hydrogen evolution activity of the composite materials. The hydrogen evolution rate of the optimal 15%CN-CoO/CdS is 6.78-fold greater than that of pristine CdS, and is as high as 64.36 mmol·g −1 ·h −1 . Meanwhile, the 15%CN-CoO/CdS exhibits outstanding chemical stability after cyclic hydrogen production experiment for 30 h, and its apparent quantum efficiency (AQE) reaches 27.47% under monochromatic light at 405 nm. In addition, the formation process and photocatalytic hydrogen evolution mechanism of the CN-CoO/CdS p-n type heterojunctions are analyzed and discussed. This work provides a new idea for the construction of efficient photocatalytic heterojunctions through the modification and combination of semiconductors.