Surface functional modification through small organic molecules to form surface complex which possess unique electronic and optical properties, is a hopeful strategy in activating BiOCl-0 1 0 for visible light harvesting. However, the significant charge transfer between surface complex and BiOCl-0 1 0 in photocatalytic process is vague. In this work, we ingeniously design a facile repeat experiment to obtain reliable information on charge transfer mechanisms and structure-reactivity relationships between surface complex and BiOCl-0 1 0 under reaction condition, Interestingly, this charge transfer gives rise to the formation of defects which are protected by a disordered outer layer on surface. Moreover, the introduction of defects plays a vital role in photocatalytic and photoelectric performance, which can be verified by DFT calculations. Our current work is expected to offer new insight into charge transfer between surface complex and substrates for better understanding to photocatalytic reactions and for rational design and synthesis of photocatalyst with high activity. (C) 2014 Elsevier B.V. All rights reserved.