Nitrogen-doped, proton-exchanged Dion-Jacobson layered niobate perovskites for photocatalytic hydrogen generation in solar light

Wide band gap semiconductor niobate photocatalysts with Dion-Jacobson layered perovskite structure were nitrogen-doped via simple gas-solid reaction to extend their absorption into the visible light range. Nitrogen doping was performed using ammonia as precursor, resulting in decreased band gaps of doped AB2Nb3O10 compounds (A = Cs, Rb, K; B = Ca, Sr) down to 2.5 eV. The resulting materials were investigated concerning their chemical and electronic structures. Nitrogen-doped AB2Nb3O10 crystals showed a clear red shift in absorption. Photocatalytic performance tests for the doped materials evaluated the capability of H2 production under simulated solar irradiation. The addition of carbonates to the gas-solid reaction turned out to be advantageous for the reduction of defects and the preservation of photocatalytic activity of nitrogen-doped layered niobates AB2Nb3O10.