Mastering the electrochemical interfaces for developing improved water splitting electrocatalysts – MIDWAY

The efficient production, storage and use of clean energy at large scale is arguably one of the major challenges that society will have to face in the next decades. The dependence of the current energy sector on dwindling fossil fuel resources makes this a timely concern for the next generation of scientists. The deployment of renewable energy carriers is largely hampered by inefficient energy storage and conversion devices. Technologies with high energy density such as water splitting/fuel cells suffer from poor efficiencies because the involved processes at solid/liquid and solid/solid interfaces are far from being understood and optimized. In particular, sluggish kinetics associated with the oxygen evolution reaction (OER) is one of the major roadblocks preventing the development of electrolyzers. Numerous studies were devoted to the development of cost-effective and efficient transition metal oxides as OER catalsysts as well as to the understanding of the complex reaction taking place on their surfaces. Even though major findings were made, no OER catalyst satisfies for the moment industrial targets in terms of activity and durability.

Nevertheless, very recent findings pointed out that the OER activity can be sensibly enhanced by activating surface oxygen as active site for the reaction to proceed. Doing so, the reaction proceed through a newly uncovered mechanism for which the O-O bond formation is no more the rate limiting step, but rather the proton transfer becomes kinetically limiting. Unfortunately, we also understand that enhancing the OER activity of transition metal oxides by triggering the participation of surface oxygen to the reaction is at the expense of the stability of these catalysts. Hence, the competition is fierce among researchers to provide the adequate solution to this equation. Indeed, this correlation defines a hard line for the development of new OER catalysts and we can already foresee that it will not be overcome by using a classical approach based on controlling the surface binding energy of intermediates to the reaction. Instead, researchers have to look for extrinsic properties so to independently control the activity and the stability of the catalysts. For that, we must look at the catalyst at a different scale and consider the interfaces involved into the reaction, i.e. the solid/liquid and the solid/solid interface.

In MIDWAY, a dual materials science/chemistry approach will be pursued to combat the limitations pertaining to the development of OER catalysts. For that, we propose to use to our own advantage the oxidation reaction occurring when triggering the redox activity of surface oxygen. The main goal is to prepare perovskite catalysts and activate their surface through a selective oxidation process. Doing so, we aim at understanding better the charge compensation mechanism occurring at the bulk/surface interface and the limitations related associated to the proton exchange and diffusion from the surface to the electrolyte to circumvent them. To study these complex phenomena and interfaces, the development of unique tools will be needed. Hence, online electrochemical mass spectroscopy (OLEMS) cell, in situ cells for X-ray absorption spectroscopy (XAS) and electrochemical setup for the in situ determination of the nature of the catalyst/substrate junction by Mott Schottky measurements will be developed hand to hand with the acquisition of fundamental understanding to the science underpinning the OER reaction.