Enhancing Low‐Bias Performance of Hematite Photoanodes for Solar Water Splitting by Simultaneous Reduction of Bulk, Interface, and Surface Recombination Pathways

For a hematite (α-Fe2O3) photoanode, multiple electron/hole recombination pathways occurring in the bulk, interfaces, and surfaces largely limit its low-bias performance (low photocurrent density at low-bias potential) for photoelectrochemical water splitting. Here, a facile and rapid three-step approach is reported to simultaneously reduce these recombinations for hematite nanorods (NRs) array photoanode, leading to a greatly improved photocurrent density at low bias potential. First, flame-doping enables high concentration of Ti doping without hampering the morphology and surface properties of the hematite NRs, which reduces both the bulk and surface recombinations effectively. Second, the addition of a dense-layer between the hematite NRs and fluorine-doped SnO2 substrate effectively reduces the interfacial recombination by suppressing the electron back-injection into electrolyte. Finally, the sequential oxalic acid etching and FeOOH deposition improves both the interface quality between FeOOH electrocatalyst and hematite NRs and the surface catalytic activity. Significantly, the combination of flame-doping, dense-layer deposition, surface etching, and electrocatalyst deposition effectively reduces the multiple electron/hole recombination pathways in a hematite NRs photoanode, which decreases the photocurrent onset potential from 1.02 V RHE to 0.64 VRHE, a reduction of 380 mV.