To reduce energy losses in water electrolysers a fundamental understanding of the water oxidation reaction steps is necessary to design efficient oxygen evolution catalysts. Here we present CoOx/Ti electrocatalytic films deposited by thermal and plasma enhanced chemical vapor deposition (CVD) onto titanium substrates. We report electrochemical (EC), photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) measurements. The electrochemical behavior of the samples was correlated with the chemical and electronic structure by recording XPS spectra before and after each electrochemical treatment (conditioning and cyclovoltammetry). The results show that the electrochemical behavior of CoOx/Ti strongly depends on the resulting electronic structure and composition. The thermal deposition leads to the formation of a pure Co(II)Ox which transforms to a mixed Co(II)Co(III)Ox during the OER. This change in oxidation state is coupled with a decrease in overpotential from η = 0.57 V to η = 0.43 V at 5 mA cm(-2). Plasma deposition in oxygen leads to a Co(III)-dominated mixed CoOx, that has a lower onset potential as deposited due to a higher Co(III) content in the initial deposited material. After the OER XPS results of the CoOx/Ti indicate a partial formation of hydroxides and oxyhydroxides on the oxide surface. Finally the plasma deposition in air, results in a CoOxOH2 surface, that is able to completely oxidizes during OER to an oxyhydroxide Co(III)OOH. With the in situ formed CoOOH we present a highly active catalyst for the OER (η = 0.34 at 5 mA cm(-2); η = 0.37 V at 10 mA cm(-2)).

In contrast, small-molecule organic LEDs exploiting triplet excitons using phosphorescent molecules (ph-OLEDs) or thermally activated delayed fluorescence (TADF) clearly outperform fluorescent PLEDs in terms of efficiency. The low efficiency is also detrimental for the operational stability of PLEDs, since higher currents are required to reach a required light-output, which accelerates degradation. However, to reach high efficiencies, both ph-OLEDs and TADF based OLEDs generally have complex device architectures comprising different injection, transport, emission, and blocking layers. Despite dissimilar architectures, the multilayer TADF and phosphorescent OLEDs as well as single-layer PLEDs all show typical degradation features of a voltage increase and a luminance decrease under continuous electrical operation. [4] For multilayer OLEDs the physical processes behind degradation are hard to elucidate due to the presence of many materials and interfaces. [5,6] The standard PLED device structure, being an emitting polymer layer sandwiched between two different work function electrodes, is more basic, making degradation processes more straightforward to analyze. In earlier work on degradation of poly(phenylene vinylene) (PPV) based LEDs the effects of molecular weight, molecular structure, and defects that arise during synthesis on lifetime have been discussed. [7] In particular halogen related defects in PPVs are pointed out to have a negative influence on the lifetime. With regard to physical degradation mechanisms, in 2001, Silvestre et al. [4] were the first to propose that "voltage increase" and "luminance decrease" during degradation shared a common origin, namely the formation of trap states. Furthermore, Pekkola et al. [8] studied the influence of triplet excitons on the electrical stability of conjugated polymers. A triplet sensitizer was introduced into a PPV-based LED and a negative influence of triplet excitons on the lifetime was reported. As a possible mechanism the energy transfer from a PPV triplet to an oxygen triplet state, creating the reactive singlet oxygen molecule, was suggested. [9,10] Singlet oxygen has the ability to attack the vinyl bonds of PPVs, providing a chemical pathway for degrading the material. [11] Degradation due to extrinsic effects, such as oxygen and water, is typically minimized by proper encapsulation of organic LEDs and by working in a controlled environment. [5−7,12] Also in ph-OLEDs the harmful influence of Stability under electrical stress is an important aspect for the function of organic light-emitting diodes (OLEDs). Degradation is currently one of the key topics in this field, concerning all types of OLEDs, including fluorescent-, phosphorescent-, and thermally activated delayed fluorescence-based OLEDs. For single-layer polymer light-emitting diodes (PLEDs) it has recently been found that degradation is the result of hole trap formation due to excitonpolaron interactions. However, whether singlet or triplet excitons are responsible for degradation is an open questi...