N and Sn Co-Doped hematite photoanodes for efficient solar water oxidation

Surface electron-hole recombination and low conductivity have significantly hindered the photoelectrochemical water oxidation performance of hematite. Here we report a surface N and Sn co-incorporation in hematite for efficient water oxidation, which shows a greatly enhanced photocurrent density of 2.30 mA/cm² at 1.23 V vs. RHE when compared to the pristine hematite (0.89 mA/cm²). Moreover, after the subsequent loading of Co-Pi cocatalyst, a further improved photocurrent density of 2.80 mA/cm² at 1.23 V vs. RHE can also be achieved. The excellent performance can be attributed to the synergistic effect of N and Sn in hematite, in which the surface Sn-doping could increase the donor density of hematite while the N-incorporation could adjust the amount of Sn in hematite to suppress the surface charge recombination and further increase the donor density. To the best of our knowledge, it should be the first report to reveal the synergistic effect of non-metal element N and metallic element Sn in hematite for high performance, which could be a feasible way towards the development of efficient hematite photoanodes.