As a promising visible-light-driven photocatalyst for hydrogen generation, InNbO4 of high efficiency dictates the requirements on the high specific surface area and tailored band structure that arouse increasing efforts but remain challenge. Herein, we report fabrication of nanosized InNbO4 embedded with nano-voids via apolyacrylamide sol-gel route. It exhibits excellent photocatalytic H-2 evolution rates up to similar to 68.1 mu mol.h(-1).g(-1), much better than as-reported counterparts (similar to 1 mu mol.h(-1).g(-1)) obtained via solid-state reaction or doping treatments. The particle sizes, density of nano-voids, as well as the bandgap energy are modulated by using different chelating agents, including tartaric acid (TA), citric acid (CA), acetic acid (AA). Based on high resolution high angle annular dark-field (HAADF) characterizations, it interesting to discover that the photocatalytic performance shows obvious dependence on the voids size. Nano-voids (2-8 tim) can maximize the specific surface and thus enhance the photocatalytic performance, while lattice-scale voids (<1.5 nm) may become a carrier trapping defects and thus decrease the photocatalytic performance. This work lays a foundation for further promoting activity of InNbO4 photocatalysts through balanced optimization of microstructure and band structure. (C) 2016 Elsevier B.V. All rights reserved.