Electronic Supplementary Materials

ELECTRONIC SUPPLEMENTARY MATERIALS

Copper Hexacyanoferrate Modified Electrodes for Hydrogen Peroxide Detection as Studied by X-Ray Absorption Spectroscopy

Marco Giorgetti*a, Domenica Tonellia, Mario Berrettonib, Giuliana Aquilantic, Marco Minicuccid

a Department of Industrial Chemistry”Toso Montanari”, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy, and INSTM, UdR Bologna;

b Department of Industrial Chemistry”Toso Montanari”, UOs (unità operativa di sede) Campus di RIMINI, University of Bologna, and INSTM, UdR Bologna;

c Sincrotrone Trieste S.C.p.A., S.S. 14 Km 163.5, 34149 Basovizza, Trieste, Italy;

d CNISM, School of Science and Technology, Physics Division, University of Camerino, Via Madonna delle Carceri, 62032 Camerino (MC), Italy;

Figure S1. Series of normalized XANES spectra taken at the Cu K-edge of CuHCF based electrodes. The perfect matches of the three curves for each electrode (CuHCF and Cu2+ loaded CuHCF) demonstrated the reproducibility of the local structure for the two type of electrodes.

XANES Linear Combination CuHCF / H2O2

Cu2+-loaded à high additions

Cu2+-loaded à low additions

CuHCF à high additions

CuHCF à low additions

Figure S2. Linear Combination Fitting (LCF) analysis of the XANES spectra at the Fe K-edge for the two studied electrodes at two different concentration range of H2O2 addition. Red and black curves are related to the experimental and fit, respectively.

Figure S3. Examples of cyclic voltammetry recorded after the various hydrogen peroxide additions protocol for electrodes N, C, O. The formal potential Ef = (Ep,anodic + Ep,cathodic)/2 are 0.687, 0.691, and 0.681, respectively for electrodes N, C, O. This values falls in the formal potential observed for copper hexacyanoferrate (see Ref. 33), excluding the presence of a iron/copper hexacyanoferrate solid solution.

Figure S4. Comparison of non-normalized XANES curves at the Fe K-edge for electrodes O and C. The progressive decreasing in the intensities of the edge upon hydrogen peroxide addition reveals the partial dissolution of the CuHCF film. The geometrical position of the electrode into the sample holder were checked out carefully in order to ensure that the same portion of the material were probed by the beam stream during the various measurements, but an error of about 10% must be considered.

Figure S5. EXAFS fitting procedure. Best fit of the Cu K-edge EXAFS signals of the CuHCF and Cu2+-loaded CuHCF electrodes. The comparison of the experimental (solid lines) with the theoretical (dotted lines) k2-extracted EXAFS signal is displayed for the pristine electrode and after 0.28 mol dm-3 H2O2 addition and after step ii) and iii) or the hydrogen peroxide addition protocol. As seen from the figure, measurements after addition of hydrogen peroxide are characterized by a large noise which limits the EXAFS data to about 0.9-1 nm-1. In the fitting procedure, the E0 value was found to be 8990 eV, which is displaced by several eV in respect to the edge inflection point. The values of S02 were found in the 0.77-0.89 range and are in agreement with previous studies [20,28].