Enhancing Majority Carrier Transport in WO3 Water Oxidation Photoanode via Electrochemical Doping

Here we report an electrochemical reduction-induced photocurrent enhancement up to an order of magnitude for monoclinic tungsten trioxide (WO3) particulate photoanodes. Electrochemical impedance and photoelectrochemical measurements suggest that the improved performance is attributed to the increase in majority carrier concentration (from 1.5 x 10(18) to 2.5 x 10(21) cm(-3)). This results in higher conductivity and improved electron transport. Minority carrier extraction can be increased by reducing the WO3 particle size from 200 nm to 50 and 30 nm. The larger solid-liquid interface area promotes the water oxidation rate. By balancing electron/hole extraction with photon absorption in an optimized 30 nm WO3 particulate electrode, a record water oxidation photocurrent of 3.8 mA/cm(2), under +1.36 V (vs. RHE) applied bias in 0.1 M Na2SO4 solution at pH = 3.5 is achieved with 50 mW/cm(2) unfiltered Xe illumination. (C) The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.