An Approach to Enhance PEC Water Splitting Performance through Al:Ti Codoping in Hematite (α-Fe<sub>2</sub>O<sub>3</sub>) Photoanode: The Effect of Al<sup>3+</sup>as a Codopant
Sourav Chaule, Jihun Kang, Balaji G. Ghule, Hyunmin Kim, Ji‐Hyun Jang
Abstract
We achieved improved photoelectrochemical (PEC) efficiency by inducing strain through substitutional Al 3+ doping in hematite, followed by codoping with Ti 4+ . The substitution of Al 3+ for Fe 3+ induces local strain within the lattice, reducing interionic distances and thereby enhancing the charge carrier transport properties. However, theoretical findings revealed initially unfavorable formation energy when Al 3+ is doped into hematite, leading to significant lattice distortion due to size mismatch and thus limiting PEC activity. Co-doping Al 3+ with Ti 4+ in Fe 2 O 3 restored the lattice symmetry by alleviating strain, resulting in a favorable formation energy. Additionally, Ti 4+ contributes excess electrons, further increasing the electrical conductivity. By leveraging formation energy control through Ti doping, our optimized Al:Ti–Fe 2 O 3 with a cocatalyst exhibited a photocurrent density of 4.00 mA cm –2 at 1.23 V RHE, representing a 6.5-fold improvement over Fe 2 O 3 alone. Our study proposes an approach for utilizing Al 3+ as a codopant in Fe 2 O 3, which can potentially be extended to other codoped systems.