Synthesis of new ferrite, Al–Cu ferrite, and its oxygen deficiency for solar H2 generation from H2O

The solar H2 generation with the oxygen deficiency of Al–Cu ferrite (AlaCubFecO4AlaCubFecO4, 3a+b+3c=83a+b+3c=8) has been studied for application to conversion of solar thermal energy to chemical energy of H2. The Al–Cu ferrite was newly synthesized with different Al:Cu:Fe mole ratios from the co-precipitate of their nitrates. The Al–Cu ferrite (Al:Cu:Fe mole ratios = 0.43:0.43:2.14) prepared at 1473 K was the single phase of the spinel type compound. The cyclic two-step water splitting reactions (O2 releasing and H2 generation reactions) using the Al–Cu ferrite (Al:Cu:Fe==0.43:0.43:2.14) gave the O2 and H2 yields of 1.6 and 0.37%, respectively. In the O2 releasing reaction, the Al–Cu ferrite changes to the oxygen deficient form of spinel structure. The temperature (T=1673K) of the O2 releasing reaction with Al–Cu ferrite was lowered by ca. 100 K than those of Zn ferrite and Ni ferrite systems.