An in situ ion filtration-precipitation method was reported for fast assembling 3D GAs composite.
Nano-sized Ag3PO4 were well-dispersed throughout the interconnected structure of 3D GAs.
3D GAs enhanced photo-generated charges separation and transfer in 3D Ag3PO4/GAs.
3D Ag3PO4/GAs exhibited superior photocatalytic activity and stability in water splitting.