光催化-碘掺杂二氧化钛XPS的问题？

“the iodine-doped titanium dioxide was prepared by the doped potassium iodide, and why there is not potassium element, so authors provide analyses (xps) and reasons.”以碘化钾为碘源制备碘掺杂的二氧化钛，XPS中没有钾元素，问为什么？??求解