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Non-oxide cobalt based water oxidation electrocatalysts have received attention recently for their relative ease in preparation since they are easy to prepare, stable both in acidic & basic media, and they have higher turnover frequencies compared to cobalt oxides. Recent studies show that one of the main bottlenecks in implementing non-oxide systems to water splitting is the low number of active metal sites, which is in the order of nmol.cm−2. Herein a new series of non-oxide water oxidation catalysts have been introduced to the field. Cobalt dicyanamides are observed to have around four times higher surface active sites and better catalytic performances than cyanide based systems. Long term catalytic studies (70 h) at an applied potential of 1.2 V and electrochemical studies performed in solutions in pHs ranging from 3.0 to 12.0 indicate that the compounds are robust and retain their structures even under drastic conditions. Moreover, addition of nickel impurities to cobalt dicyanamides has been introduced as a feasible method to improve their catalytic activities.

The development of new water oxidation electrocatalysts that are both stable and efficient, particularly in neutral conditions, holds great promise for overall water splitting. In this study, the electrocatalytic water oxidation performance of a new cobalt-based catalyst, Co3(BO3)2, with a Kotoite-type crystal structure is investigated under neutral conditions. The catalyst is also hybridized with CNTs to enhance its electrocatalytic properties. A remarkable increase in catalytic current along with a significant shift in the onset overpotential is observed in Co3(BO3)2@CNT. Additionally, CNT addition also greatly influences the surface concentration of the catalyst: 12.7 nmol cm−2 for Co3(BO3)2@CNT compared with 3.9 nmol cm−2 for Co3(BO3)2. Co3(BO3)2@CNT demands overpotentials of 303 and 487 mV to attain current densities of 1 and 10 mA cm−2, respectively, at pH 7. Electrochemical and characterization studies performed over varying pH conditions reveal that the catalyst retains its stability over a pH range of 3-14. Multi-reference quantum chemical calculations are performed to study the nature of the active cobalt sites and the effect of boron atoms on the activity of the cobalt ions. The authors thank the Science and Technology Council of Turkey, TUBITAK (Project No: 214Z095) for financial support. E.U. thanks TUBITAK for support (Project No: 1929B011500059). Y.D. thanks BAGEP and TÜBA-GEBİP for young investigator awards and ECOSTBio (CM 1305) for support. TUBITAK TRGRID infrastructure is gratefully acknowledged for HPC resources.

A Pt electrode modified by polyaniline–poly(3-methylthiophene)–poly(3,3′-diaminobenzidine) was used for amperometric determination of epinephrine in a solution of NaHSO4/Na2SO4 (pH 2.0). For these studies, potentials between 0.40 and 0.50 V were applied, and the best response was obtained at 0.45 V. The limit of detection, limit of quantification, and the linear dynamic range were 1.23 × 10−4, 4.10 × 10−4, and 4.10 × 10−4 to 100.0 mmol L−1, respectively. These results were compared with determinations using Pt electrodes that were coated and uncoated with homopolymers. To check the accuracy of the developed method and the matrices interference, determination of epinephrine was performed in human serum samples using this modified electrode. The epinephrine concentrations were adjusted to 1.0 and 5.0 mmol L−1, and recovery values were calculated as 100.4% and 96.8%, respectively. It is significant that the determination of epinephrine was carried out at a lower potential (0.45 V) than the oxidation potential of epinephrine (0.65 V) without any matrix effect.

Although several Prussian Blue analogues (PBAs) have been investigated as water oxidation catalysts, the field lacks a comprehensive study that focuses on the design of the ideal PBA for this purpose. Here, members of a series of PBAs with different cyanide precursors have been investigated to study the effect of hexacyanometal groups on their electrocatalytic water oxidation activities. Cyclic voltammetric, chronoamperometric, and chronopotentiometric measurements have revealed a close relationship between the electron density of electroactive cobalt sites and electrocatalytic activity, which has also been confirmed by infrared and XPS studies. Furthermore, pH-dependent cyclic voltammetry and computational studies have been performed to gain insight into the catalytic mechanism and electronic structure of cyanide-based systems to identify possible intermediates and to assign the rate-determining step of the target process. The authors thank the Science and Technology Council of Turkey, TUBITAK (Project No. 215Z249) for financial support. E.U. thanks TUBITAK for support (Project No. 1929B011500059). Y.D. acknowledges ECOSTBio (CM 1305) for support and thanks the M.N. Parlar Foundation, BAGEP, and TÜBA-GEBİP for young investigator awards. TUBITAK TRGRID infrastructure is gratefully acknowledged for HPC resources. We also thank Prof. Burak Ülgüt for helpful discussions on electrochemistry.