The scientific field in which the work contained in this thesis resides to, is
the broader field of catalysis. A systematic work of designing and evaluating
new materials for efficient electrochemical water splitting is presented in the
papers included in the dissertation. In particular, the oxygen evolution reaction
(OER) is investigated mainly by implementing density functional (DFT) theory
calculations and a part of experimental work.
With OER being the main drawback of the water splitting procedure many
efforts both theoretically and experimentally have been made to optimize
the reaction and thus increase the efficiency of the process. A literature
work including multiple theoretical studies of the last decade concerning OER
consists the first paper of the thesis. This work identifies the reasons why
despite the immense theoretical efforts for optimizing water oxidation, very
little has been achieved in terms of succeeding a higher efficiency. The scaling
relations between the HO and HOO intermediates are once more identified to
be the fundamental limitation of OER. A computational artifact is also observed,
one creating misconceptions concerning the activity of semiconductors towards
the reaction. The fact that the scaling relations are so robust and extremely
difficult to overcome, revealed the need of finding materials as active as stateof-
the-art catalysts, like IrO2 and RuO2, but less expensive and adequately
stable under the harsh OER working conditions. The second study of this
thesis proposes a way of tuning the electronic structure of semiconductors
by incorporating both p-type and n-type dopants with a scope to increase
their catalytic activity while preserving the inherit stability of semiconducting
materials like TiO2.
LaNiO3 is a material well known for its stability and its relative good performance in alkaline water electrolysis. Those facts are making LaNiO3 a suitable candidate for further optimization. The third paper of the thesis is an excellent paradigm of the synergy between theory and experiment since the theoretical predictions for the activity of modified LaNiO3 surfaces are in great agreement with the experimental data. The combination of the DFT calculations and the structural characterization of the LaNiO3 nanoparticles reveals the OER
mechanism on the modified surfaces elucidating why the modified structures
are more active than the pure LaNiO3 nanoparticles.
In the last paper of the thesis, an experimental work concerning doped pyrochlore nanoparticles which are evaluated for their catalytic performance
towards OER is reported. The structural modifications due to doping, increases
the activity of the nanoparticles to a level that are comparable to the state-of-the-art catalysts. The DFT calculations also predict the structural modifications
revealed from the characterization of the nanoparticles but activity wise there
is a disagreement between theory and experiment exposing the DFT limitations
when dealing with strong correlated systems.
The conclusions of this thesis are another contribution to the shared knowledge
of the scientific community in order to achieve the decarbonization of our
society and the passage to a future powered with environmental friendly fuels.