Unveiling the Significance of Diverse Valence State Second Dopants on Hf-Doped Fe<sub>2</sub>O<sub>3</sub> Photoanodes for Enhanced Photoelectrochemical Water Splitting
Periyasamy Anushkkaran, Yong Bi Kwon, Tae Sik Koh, Seong Hui Kim, Weon‐Sik Chae, Sun Hee Choi, Hyun Hwi Lee, Jungwon Kim, Jum Suk Jang
Abstract
Hematite (α-Fe 2 O 3 )-based photoanodes offer great potential for use in solar hydrogen production as part of efforts to construct a sustainable and renewable energy economy based on photoelectrochemical (PEC) water splitting. A co-doping modification is of the utmost significance for improving PEC performance. To develop an efficient photoanode, a comprehensive grasp of co-dopants with diverse valence states is necessary. Herein, we describe a hydrothermal and dip-coating approach to the fabrication of Hf-doped Fe 2 O 3 (Hf-HT) photoanodes co-doped with Be 2+, Al 3+, Si 4+, and Nb 5+ and evaluate the influence of each co-dopant on PEC performance. The PEC characteristic results revealed that Be 2+ and Al 3+ co-dopants enhanced surface charge separation efficiency, thus accelerating charge transfers at the photoanode–electrolyte interface. Meanwhile, the PEC performance of the Hf-HT photoanode co-doped with Nb did not significantly improve because of the thick Nb 2 O 5 overlayer. However, the use of a Si 4+ co-dopant improved the bulk properties of the photoanode. An optimized Hf-HT photoanode co-doped with Be achieved a photocurrent density of 1.98 mA/cm 2 at 1.23 V RHE . This demonstrates that ex situ co-doping can have both positive and negative impacts on the PEC activity of photoelectrodes, and the co-dopants used to accomplish the desired outcomes should be considered in detail.