Metal-filaments strengthened thin-films were rationally designed to serve as freestanding and defective electrodes for renewable energy applications. A transformative nanomanufacturing process was developed to fabricate these thin-film electrodes (mixed oxides of iron group metals) with nanoporous structure and controllable composition in a facile and scalable manner. More specifically, electrodeposition and anodic treatments were employed to produce freestanding and defective NiFe oxides nanoporous layers (NPL). These NPL can be directly used as flexible and additive-free electrodes for renewable energy generation (water splitting) and storage (supercapacitor) applications without using binders, current collector and other additives. Significantly enhanced electrochemical performances were therefore achieved due to the unique merits of these NPL: i) highly porous structure considerably increase the electrode/electrolyte interface, which facilitates the electrochemical reaction; ii) these defective NPL provide a large number of active sites (defects) for electrochemical reactions; iii) residual metal-filaments in the NPL form an interconnected conductive framework, which drastically improves the flexibility and conductivity of the electrode.