Enhancement of nitrogen-doped TiO₂ photocatalysts due to the surface deposition of Pd and Pt is investigated.

This review deals with the destabilization methods for improvement of storage properties of metal hydrides. Both theoretical and experimental approaches were used to point out the influence of various types of defects on structure and stability of hydrides. As a case study, Mg, and Ni based hydrides has been investigated. Theoretical studies, mainly carried out within various implementations of DFT, are a powerful tool to study mostly MgH₂based materials. By providing an insight on metal‐hydrogen bonding that governs both thermodynamics and hydrogen kinetics, they allow us to describe phenomena to which experimental methods have a limited access or do not have it at all: to follow the hydrogen sorption reaction on a specific metal surface and hydrogen induced phase transformations, to describe structure of phase boundaries or to explain the impact of defects or various additives on MgH₂stability and hydrogen sorption kinetics. In several cases theoretical calculations reveal themselves as being able to predict new properties of materials, including the ways to modify Mg or MgH₂that would lead to better characteristics in terms of hydrogen storage. The influence of ion irradiation and mechanical milling with and without additives has been discussed. Ion irradiation is the way to introduce a well‐defined concentration of defects (Frankel pairs) at the surface and sub‐surface layers of a material. Defects at the surface play the main role in sorption reaction since they enhance the dissociation of hydrogen. On the other hand, ball‐milling introduce defects through the entire sample volume, refine the structure and thus decrease the path for hydrogen diffusion. Two Severe Plastic Deformation techniques were used to better understand the hydrogenation/dehydrogenation kinetics of Mg‐ and Mg₂Ni‐based alloys: Equal‐Angular‐Channel‐Pressing and Fast‐Forging. Successive ECAP passes leads to refinement of the microstructure of AZ31 ingots and to instalment therein of high densities of defects. Depending on mode, number and temperature of ECAP passes, the H‐sorption kinetics have been improved satisfactorily without any additive for mass H‐storage applications considering the relative speed of the shaping procedure. A qualitative understanding of the kinetic advanced principles has been built. Fast‐Forging was used for a “quasi‐instantaneous” synthesis of Mg/Mg₂Ni‐based composites. Hydrogenation of the as‐received almost bi‐phased materials remains rather slow as generally observed elsewhere, whatever are multiple and different techniques used to deliver the composite alloys. However, our preliminary results suggest that a synergic hydrogenation / dehydrogenation process should assist hydrogen transfers from Mg/Mg₂Ni on one side to MgH₂/Mg₂NiH₄on the other side via the rather stable a‐Mg₂NiH_0.3, acting as in‐situ catalyser.

Incorporation of suitable dopants in MgH₂ is widely investigated as the way of improving hydrogen storage characteristics of this material.

Mg₂FeH₆ is a promising hydrogen storage material with one of the highest volumetric hydrogen density among the known hydrogen storage materials. However, its complicated synthesis and high temperature of hydrogen desorption limit wider applications. In this paper we study the influence of transition metal (Ni, Co, Mn) doping on the structural, electronic and hydrogen sorption properties of Mg₂FeH₆, using first-principles density functional theory calculations. The thermodynamics of three different synthesis routes is addressed, and all of the mentioned transition metals are found to destabilize Mg₂FeH₆. In addition, a detailed study of electronic structure properties, including densities of states (DOS) and charge transfer analysis (AIM), reveals that the doping with Ni, Mn and Co leads to the reduction of the direct band gap of Mg₂FeH₆.