Finding photostable,first-row transition metal-based molecular systems for photocatalytic water oxidation is as tep towards sustainable solar fuel production. Herein, we discovered that nickel(II) hydrophilic porphyrins are molecular catalysts for photocatalytic water oxidation in neutral to acidic aqueous solutions using [Ru(bpy) 3 ] 2+ as photosensitizer and [S 2 O 8 ] 2À as sacrificial electron acceptor.E lectron-poorer Niporphyrins bearing 8f luorine or 4methylpyridinium substituents as electron-poorer porphyrins afforded 6-fold higher turnover frequencies (TOFs;c a. 0.65 min À1 )t han electronricher analogues.H owever,t he electron-poorest Ni-porphyrin bearing 16 fluorine substituents was photocatalytically inactive under such conditions,because the potential at which catalytic O 2 evolution starts was too high (+ 1.23 Vv s. NHE) to be driven by the photochemically generated [Ru(bpy) 3 ] 3+ .C ritically,these Ni-porphyrin catalysts showed excellent stability in photocatalytic conditions,a sas econd photocatalytic run replenished with an ew dose of photosensitizer,a fforded only 1-3 %less O 2 than during the first photocatalytic run.[*] C. Liu, D. van den Bos, B. den Hartog, D. van der Meij, A
A water-soluble binuclear Cu complex, synthesized using a polypyridine-polyamide ligand, was able to catalyze oxygen reduction to water from neutral aqueous solutions. Electrocatalytic results suggested that one Cu center was first reduced by one electron to form a CuCu species, which reacted with O to give a superoxide radical intermediate.
While exploring the process of CO/CO2 electroreduction (COxRR) is of great significance to achieve carbon recycling, deciphering reaction mechanisms so as to further design catalytic systems able to overcome sluggish kinetics remains challenging. In this work, a model single-Co-atom catalyst with well-defined coordination structure is developed and employed as a platform to unravel the underlying reaction mechanism of COxRR. The as-prepared single-Co-atom catalyst exhibits a maximum methanol Faradaic efficiency as high as 65% at 30 mA/cm2 in a membrane electrode assembly electrolyzer, while on the contrary, the reduction pathway of CO2 to methanol is strongly decreased in CO2RR. In-situ X-ray absorption and Fourier-transform infrared spectroscopies point to a different adsorption configuration of *CO intermediate in CORR as compared to that in CO2RR, with a weaker stretching vibration of the C–O bond in the former case. Theoretical calculations further evidence the low energy barrier for the formation of a H-CoPc-CO– species, which is a critical factor in promoting the electrochemical reduction of CO to methanol.
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