Using the particular XPEEM geometry we access both surface and bulk chemical and coordination properties at nanoscale. We could thus evidence modifications of O K-edge spectra directly linked to the formation of surface Ti-rich phase promoting surface states in the unoccupied DOS. We report here, for the first time , spectro-ptychography measurements at Ti L2,3 absorption edges. We demonstrate how very strong chemical coordination sensitivity allows probing surface clusters as small as 10 nm. DFT calculations and complementary STEM measurements consolidated our findings, confirming the formation of pseudobrookite clusters at the surface of Ti-doped hematite nanoparticles. These clusters are the origin of the enhanced PEC activity. Finally, we show that low-tech approach allows escalating solar water splitting efficiency of photoanodes obtained from earth abundant material.