Highly nanoporous hematite with optimal doping for an efficient photoelectrochemical water splitting

Abstract

In this study, we propose a highly nanoporous hematite structure having under 5 nm hole diffusion pathways via an optimized doping method based on Density Functional Theory (DFT) calculations. The superiority of highly nanoporous structure with the synergistic effects of a facilitated Kirkendall effect and optimal doping condition were clearly proved by the experimental analyses. The optimized prous photoanode prepared with an optimal doping conditoin (Ge:Ti:Sn doped hematite) and the subsequent dopositon of an oxygen evolution reaction co-catalyst NiFe(OH)x showed a maximum photocurrent density of 5.1 mA cm-2 at 1.23 VRHE, which is 3.3-fold higher than that of reference Ti:Sn hematite due to enhanced surface reaction kinetics. This study provides a significant breakthrough in dramatically improving the low PEC performance of hematite-based photoanodes with an short-hole diffusion pathway issue through optimal co-doping and nanostructuring.