Hydrogen evolution through photoelectrochemical (PEC) water splitting by tungsten oxide based photoanodes, as a stable and environmental-friendly material with moderate band gap, has attracted significant interest in recent years. The performance of WO3 photoanode could be hindered by its poor oxygen evolution reaction kinetics and high charge carrier recombination rate. Additionally, scalable and cost-effective commercial procedure to prepare nanostructured electrodes is still challenging. We present, for the first time, a novel and scalable method to fabricate highly efficient self-supported WO3/W nanostructured photoanodes from commercial W-Cu powder metallurgy (P/M) parts for water splitting. The electrodes were prepared by electrochemical etching of Cu networks followed by hydrothermal growth of WO3 nanoflakes. Interconnected channels of W skeleton provided high active surface area for the growth of WO3 nanoflakes with a thickness of similar to 40 nm and lateral dimension of similar to 250 nm. The optimized photoelectrode having 35% interconnected porosity exhibited an impressive current density of 4.36 mA cm(-2) comprising a remarkable photocurrent of 1.71 mA cm(-2) at 1.23 V vs. RHE under 100 mW cm(-2) simulated sunlight. This achievement is amongst the highest reported photocurrents for WO3 photoelectrodes with tungsten substrate reported so far. Impedance and Mott-Schottky analyses evidenced fast charge transfer, low recombination rate, and accelerated O-2 detachment provided by optimum 3D porous WO3/W electrode. Due to the nature of the commercial P/M parts and low-temperature hydrothermal processing, the procedure is cost-effective and scalable which can pave a new route for the fabrication of highly porous and efficient water splitting electrodes. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.