Electrolyte Effects on the Electrocatalytic Performance of Iridium‐Based Nanoparticles for Oxygen Evolution in Rotating Disc Electrodes

Abstract

Proton exchange membrane water electrolysers are very promising renewable energy conversion devices that produce hydrogen from sustainable feedstocks. These devices are mainly limited by the sluggish kinetics of the oxygen evolution reaction (OER). Ir‐based nanoparticles are both reasonably active and stable for the OER in acidic media. The electrolyte composition and the pH may play a crucial role in electrocatalysis, yet they have been widely overlooked for the OER. Herein, we present a study on the effects of the composition and concentration of the electrolyte on commercial Ir black nanoparticles using concentrations of 0.05 M, 0.1 M and 0.5 M of both sulphuric and perchloric acid. The results show an important effect of the electrolyte composition on the catalytic performance of the Ir nanoparticles. The concentration of H2SO4 interferes on the oxidation of Ir and decreases the catalytic performance of the catalyst. HClO4 does not show strong interferences in the electrochemistry of Ir. Higher catalytic performances are observed in HClO4 electrolytes in comparison to H2SO4 with little effect of the concentration of HClO4.

Synthesis of Iridium Nanocatalysts for Water Oxidation in Acid: Effect of the Surfactant

“…Chronopotentiometric studies have to be analysed carefully as they can give misleading interpretation of the catalytic performance of different materials. We recently showed that the initial overpotential in chronopotentiometric studies determines the apparent stability of Ir NPs as the rate of degradation is much faster at higher overpotentials . In this work, the initial overpotentials of the different Ir NPs are similar (Figure a).…”

“…To ensure a sustainable use of this precious metal, a careful design of the catalyst is needed . Much effort has been recently devoted to develop Ir‐based nanoparticulate catalysts to maximise the electrochemical activity per amount of Ir …”

Ir/TiONx/C high-performance oxygen evolution reaction nanocomposite electrocatalysts in acidic media: synthesis, characterization and electrochemical benchmarking protocol

“…There is no agreement on an OER activation protocol, but in general, two different methods can be used. Sometimes, the electrode is cycled under OER potential range until a stable CV is reached [30,53], but most frequently fast cycling between a low potential (like 0.05 V or 0.025 V versus RHE) and a potential close to the onset of OER (between 1.3 V and 1.45 V versus RHE) is employed until stable CVs are reached [20,29,36,38,39]. In the present study, two different potential windows were compared.…”

“…The second activation consisted of cycling between 0.05 and 1.45 V versus RHE. This second protocol is similar or closer to the potential range usually chosen in the literature [20,29,36,38,39]. The OER activity was recorded by performing a minimum of eight cycles between 1.2 and 1.6 V versus RHE, 1600 rpm, 20 mV s −1 , under Ar atmosphere in a 0.1 M HClO 4 (Merck, Suprapur, 70%) electrolyte.…”

“…For instance, due to the lack of unified benchmark protocols in the OER community, many different activity parameters are used (the value of current at 1.55 V, 1.6 V or the value of voltage at 10 mA cm −2 , etc [27,28]), which then results in an inability to compare the outcomes between different groups. Moreover, parameters like an activation protocol or the loading of the catalyst, which would assure reproducibility of measurements, are lacking in systematic study and standardized protocols, besides a few recent studies [12,[29][30][31]. Even though some important parameters have already been assessed (impact of the electrolyte [29], the backing electrode [32], the gas saturation [33] or rotation speed [34]), they are rarely taken into account when presenting results.…”