Abstract: A method for producing hydrogen wherein use is made of a high temperature steam electrolysis apparatus having an electrolysis vessel being partitioned into the anode side and the cathode side by the use of a solid oxide electrolyte film as a diaphragm, steam is fed to the above cathode side and a reducing gas is fed to the anode side, and steam electrolysis is carried out at a high temperature, characterized in that the reducing gas and the steam fed to the electrolysis vessel has a temperature of 200 to 500° C.

Abstract: An object of the present invention is to provide a structure of a metal collecting material for use in seawater or river water or industrial wastewater to give the most excellent adsorption efficiency. Another object of the present invention is to provide a process for efficiently separating and recovering valuable metals or noxious metals from a metal collecting material having collected said valuable metals from seawater or noxious metals from river water or wastewater with the least possible waste generation. A metal collector according to an aspect of the present invention is formed by stacking at least partially alternate layers of a fibrous metal collecting material with a spacer for introducing a liquid to be treated into said collecting material, wherein the area of spacer side faces represents 25-75% of the total area of collecting material side faces and spacer side faces in the side faces of the stack.