Design and development of visible-light-active electrode materials with efficient charge separation and enhanced stability are the main criteria for solar energy conversion in photoelectrochemical devices. Herein, we report a new metal-free photoactive polymer containing thiadiazole and triazine units with a stable photo-electroactivity in strong acidic electrolytes. The reactivity of chloro groups in cyanuric chloride and the nucleophilic substitution with 2,5-dimercapto-1,3,5-thiadiazole favors the facile (electro)copolymerization at lower oxidative potentials. Spectral investigations reveal the systematic bathochromic shift toward the visible region with extensive polymerization. X-ray photoelectron spectroscopy, NMR, Raman, IR, and UV−vis spectral studies evidence the substitution of chloro units with dimercapto units. This Nand S-rich poly(2,5-dimercaptothiadiazole-triazine) exhibits p-type photoactivity with the optical band gaps in the range of 2.4− 2.6 eV. On the contrary, poly-2,5-dimercaptothiadiazole displays poor n-type photoactivity. The photoelectrode shows stable, repeatable photovoltage (15−20 mV) and photocurrent (3−4 μA cm −2 ) responses in acidic electrolytes, and the incremental photocurrent responses at higher cathodic potentials for longer duration are attributed to the excellent protonation capability of polymeric units. Furthermore, they exhibit good oxygen reduction reaction electrocatalysis.
Na 3 Co III (CO 3 ) 3 was deposited on Pt and Pd electrode surfaces by a chronoamperometric technique. The deposited Na 3 Co III (CO 3 ) 3 was characterized using various surface characterization techniques. These Na 3 Co III (CO 3 ) 3 deposited electrodes are subsequently utilized for the electrocatalytic and photoelectrocatalytic methanol oxidation reaction (MOR). The MOR reaction is studied using cyclic voltammetry and chronoamperometric measurements in KOH and Na 2 CO 3 electrolytes. The Na 3 Co III (CO 3 ) 3 deposited on the Pt electrode showed enhanced current density in KOH/Na 2 CO 3 media, which relates to methanol oxidation compared with bare Pt and Na 3 Co III (CO 3 ) 3 deposited on the Pd electrode. The Na 3 Co III (CO 3 ) 3 deposited Pt electrode executes high electrocatalytic oxidation and shows an anodic peak current density of 19.7 mA cm −2 at 0.1 V vs NHE. Interestingly, the Na 3 Co III (CO 3 ) 3 deposited on the Pt electrode shows a good photoelectrocatalytic response under UV−vis light irradiation. An anodic peak current density of 22.9 mA cm −2 is observed for methanol oxidation under light irradiation. KEYWORDS: Na 3 Co III (CO 3 ) 3 , electrodeposition, cyclic voltammetry, electrochemical and photoelectrochemical behavior, methanol oxidation
With the growing population and energy demand, there is an urgent need for the production and storage of clean energy obtained from renewable resources. Water splitting electrocatalytically is a major approach to obtain clean H 2 . The efficiency, stability, and slow kinetics of anode materials developed so far do not fit the commercial application of the water oxidation reaction. To develop an efficient energy conversion catalyst, particularly for the oxygen evolution reaction (OER) herewith, Mn 2 (CO 3 ) 3 was electrodeposited on a Ni foam (NF) electrode surface by the chronoamperometric technique. The deposited Mn 2 (CO 3 ) 3 /NF was characterized using various surface characterization techniques. The electrochemical behavior of the Mn 2 (CO 3 ) 3 /NF-deposited electrode toward the OER was studied using electrochemical methods in KOH (pH 14) and NaHCO 3 (pH 8.3) electrolytes. The Mn 2 (CO 3 ) 3 /NF electrode showed a lower overpotential than CO 3 /NF and NF electrodes in the KOH/NaHCO 3 media. The Mn 2 (CO 3 ) 3 /NF electrode performs high electrocatalytic water oxidation with an overpotential of 360 mV at a current density of 10 mA•cm −2 . This overpotential is much lower than those of CO 3 /NF (460 mV) and bare NF (520 mV), with good long-term stability in the KOH medium without any catalytic degradation after 100 CV cycles and 15 h chronoamperometric studies. The stability of the electrodeposited Mn 2 (CO 3 ) 3 on the NF electrode was determined by X-ray photoelectron spectroscopy. Thus, the Mn 2 (CO 3 ) 3 /NF catalyst is suitable for the oxygen evolution reaction.
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