Series of high-cis and cis/trans poly[(fluorophenyl) acetylene]s (PFPhA) have been prepared by polymerization of (2-fluorophenyl)acetylene, (3-fluorophenyl)acetylene, and (4fluorophenyl)acetylene with catalysts: [Rh(1,5-cyclooctadiene) OCH 3 ] 2 (high-cis PFPhAs) and tungsten(VI) oxychloride/tetraphenyltin (cis/trans PFPhAs). The molecular weight and configurational stability under various conditions at room temperature were studied for both PFPhAs series by means of size exclusion chromatography, 1 H-NMR, and UV-vis techniques. All samples exhibited slow degradation when exposed to the atmosphere in the solid state; the rate of degradation was independent on the F-position on the Ph ring. The rate of degradation increased up to three orders of magnitude in the tetrahydrofuran solution where it was higher for high-cis polymers compared with their cis/trans counterparts. The degradation of high-cis PFPhAs was accompanied by significant cis-to-trans isomerization in aerated tetrahydrofuran solution. Rate of degradation and isomerization exhibited the same dependence on the F-position on the Ph ring. The hypothesis was postulated that the degradation of high-cis PFPhAs in solution was accelerated by cis-to-trans isomerization due to which the content of unpaired electrons on the main chains is enhanced. In both high-cis and cis/trans series of polymers the ortho-substituted isomers exhibited an enhanced stability compared with metaand para-substituted isomers.

Perovskite solar cells (PSCs) have proved their potential for delivering high power conversion efficiencies (PCE) alongside with low fabrication cost and high versatility. The stability and the efficiency of PSCs...

conversion and storage systems in which electrocatalytic water splitting reactions are included. [1] Hydrogen production from water electrolysis is considered a sustainable alternative since its by-product is water, but the biggest challenge in the development of electrocatalysts remains in overcoming the reaction kinetics of hydrogen evolution reaction (HER), especially in alkaline electrolytes due to additional water dissociation step which requires high overpotentials to initiate the catalysis. [2][3][4] Noble metals such as platinum, ruthenium, or iridium are conventional and satisfactory catalysts for water splitting reactions, however, their scarcity and high cost are limitations in large-scale production which has conducted intensive research to find more accessible materials to replace such precious metals. In the vast diversity of investigated materials, 2D materials have been reported as candidates for HER due to their tunable and uniformly exposed lattice planes and unique electronic state, [5,6] and among them, metal phosphorous trichalcogenides (MPX 3 ) have emerged as promising electrocatalysts. [7][8][9] Their general chemical formula is M II 2 [P 2 X 6 ] 4− , with the additional mixed metal configurations of M I 2 M II [P 2 X 6 ] 4− , and M I M III [P 2 X 6 ] 4− being possible, where X = S, Se, and in which metal cations stabilize a thiophosphate [P 2 S 6 ] 4− or selenophosphate [P 2 Se 6 ] 4− anionic framework forming layers that are weakly bonded together through van der Waals interactions. [8] Great progress has been achieved with M II 2 [P 2 X 6 ] 4− , or MPX 3 in its simplified formula, as HER electrocatalysts in alkaline media with reports on FePS 3 , [10] NiPS 3 , [11] and MnPX 3 . [12] Still in the HER region, the MPX 3 have also revealed significant enhancement for photocatalytic water splitting but the research trends remain on Fe-, [13,14] Mn-, [14,15] Cd-, [14] and ZnPX 3 [14] materials. Reports on Ni- [14] or MgPX 3 [16] materials are also found. So, all these works opened a new avenue for MPX 3 electrocatalysts thus raising interest in replacing the divalent metal with univalent and trivalent metals to investigate the catalytic performance of layered M I M III P 2 X 6 structures. A stable photoelectrochemical HER has been reported for CuInP 2 S 6 [17,18] and Ag 0.5 In 0.5 P 2 X 6 [14] compounds; however, HER in alkaline mediaConsiderable improvements in the electrocatalytic activity of 2D metal phosphorous trichalcogenides (M 2 P 2 X 6 ) have been achieved for water electrolysis, mostly with M II 2 [P 2 X 6 ] 4− as catalysts for hydrogen evolution reaction (HER). Herein, M I M III P 2 S 6 (M I = Cu, Ag; M III = Sc, V, Cr, In) are synthesized and tested for the first time as electrocatalysts in alkaline media, towards oxygen reduction reaction (ORR) and HER. AgScP 2 S 6 follows a 4 e − pathway for the ORR at 0.74 V versus reversible hydrogen electrode; CuScP 2 S 6 is active for HER, exhibiting an overpotential of 407 mV and a Tafel slope of 90 mV dec −1 . Density functional theory mod...

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