BUSCADOR RECOLECTA

10 pages. -- Figures and tables. -- Figure S1: SEM image of (a) bulk g-C3N4 and (b) ultrathin g-C3N4, (c) N2 adsorption-desorption isotherms of bCN and uCN. -- Figure S2: FTIR spectra of OAC, OLMA and TiO2 before and after ligands remove. -- Figure S3: Zeta potential distribution spectrum of TiO2 after ligands removal (a) and uCN (b). -- Figure S4: SEM image and EDS compositional maps of a T1/uCN1 composite. -- Figure S5: SEM image of T1/uCN2 and corresponding EDS spectrum. -- Figure S6: SEM image of T1/uCN2 and corresponding EDS spectrum. -- Figure S7: SEM image of T1/uCN2 and corresponding EDS spectrum; Figure S8: Chromatogram plots for 0.5 ml of standard hydrogen injected every half hour. -- Table S1: Gas Chromatography Peak Processing Data based on figure S8. -- Figure S9: Standard hydrogen curve for gas chromatography. -- Table S2: Exponential decay-fitted parameters of fluorescence lifetime of uCN, TiO2 and T1/uCN1. -- Figure S10: Photocatalytic hydrogen generation amount on bCN, TiO2 and T1/bCN1 during 4 h under simulated solar light irradiation; Table S3: Photocatalytic hydrogen production about TiO2/g-C3N4 based catalysts. -- Table S4: The AQE values with different incident light wavelengths for T1/uCN1. -- Figure S11: (a) Stability cycles of the T1/uCN1 for H2 evolution under simulated solar light irradiation; (b) TEM image of T1/uCN1 after 20 h photocatalytic H2 evolution reaction and (c) XRD pattern of T1/uCN1 before and after 20 h photocatalytic H2O2 evolution reaction., CN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCAProgramme / Generalitat de Catalunya., Peer reviewed

16 pages. -- Scheme S1. Scheme of the synthesis of Co-TAA. -- Figure S1. FT-IR spectra of the model compound Co-TAA, and Poly-TAA-Co powder. -- Figure S2. (a-b) HRTEM images and (c-d) STEM images of Poly-TAA-Co. -- Figure S3. EELS chemical composition maps from the red squared area of the STEM micrograph. Individual Co L2,3-edges at 779 eV (red), N K-edges at 401 eV (green), O K-edges at 532 eV (blue), and C-K edges at 284 eV (grey) and composites of Co-N, Co-O, Co-C, N-O and Co-N-C. -- Figure S4. (a)-(b) Survey, high resolution C1s XPS spectra of Poly-TAA powder, respectively. -- Figure S5. (a) Survey, high resolution C1s XPS spectra of Poly-TAA-Co powder, respectively. -- Figure S6 TGA analysis of Poly-TAA-Co under argon by heating to 600 ℃ at the rate of 5 ℃/min. -- Table S1. Co K-edge EXAFS fitting parameters for Poly-TAA-Co. -- Figure S7. N2 adsorption and desorption of Poly-TAA (a), Poly-TAA-Co (b) and Poly-TAA-Co-CNT (c), respectively. -- Figure S8. (a) Total current density of Poly-TAA-Co-CNT (7:3). (b) FE of CO and H2 at various potentials for Poly-TAA-Co-CNT (7:3). -- Figure S9 Current density for H2 production on Poly-TAA-Co-CNT(1:1) and Poly-TAA-Co-CNT(3:7). and. -- Figure S10. Nyquist plots of the electrochemical impedance spectroscopy (EIS) data of (a) Poly-TAA-Co, (b) Poly-TAA-Co-CNT(1:1) and Poly-TAA-Co-CNT(3:7) electrodes after the activation process. -- Figure S11. Linear sweep voltammetry (LSV) curves of (a) Poly-TAA-Co. -- Figure S12. FE of H2 at various potentials on Co-TAA-CNT(3:7), CoPc-CNT(3:7) and Poly-TAA-Co-CNT(3:7). -- Figure S13. XRD patterns of Poly-TAA-Co-CNT loaded on carbon paper before and after CO2RR. -- Figure S14 HAADF-STEM (a, c), BF-TEM (b, d) and HRTEM micrographs (c, e) of Poly-TAA-Co-CNT (3:7) sample (before and after CO2RR). -- Figure S15. EELS chemical composition maps obtained from the red squared area of the STEM micrograph. Individual Co L2,3-edges at 779 eV (red), N K-edges at 401 eV (green), O K-edges at 532 eV (blue), and C-K edges at 284 eV (grey) and composites of Co-N, Co-O, Co-C, N-O and Co-N-C. (Poly-TAA-Co-CNT (3:7), after electrocatalytic CO2RR). -- Figure S16. Calculated energy diagrams for CO2 to CO at －0.5 V conversion on CoPc and CoTAA molecule, respectively. -- Table S2. The comparison of electrochemical reduction of CO2 to CO for reported cobalt based electrocatalysts., ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and ICN2 and IREC are funded by the CERCA Programme /Generalitat de Catalunya., Peer reviewed

8 pages. -- Figure S1. SEM images of CoMoP. -- Figure S2. (a) SEM image of Co–Mo MOFs. (b–c) SEM images and (d) EDX spectrum of CoMoP. -- Figure S3. (a) SEM image of Na2MoO4-ZIF-67. (b–c) SEM images and (d) EDX spectrum Mo–CoP. -- Figure S4. (a) SEM image of ZIF-67. (b–c) SEM images and (d) EDX spectrum CoP. -- Figure S5. (a–d) TEM image of CoMoP. -- Figure S6. (a–d) HAADF-STEM micrographs of CoMoP. -- Figure S7. EELS chemical composition maps obtained from the red squared area of the STEM mi-crograph. Individual Co L2,3-edges at 779 eV (red), Mo M4,5-edges at 230 eV (green), P L2,3-edges at 132 eV (blue), N K-edge at 401 eV (pink) and C K-edge at 284 eV (orange). -- Figure S8. (a) OER and (b) HER polarization curves of CoMoP with different Mo content in 1.0 M KOH. -- Figure S9. Cyclic voltammograms for (a) CoMoP; (b) Mo–CoP; (c) CoP and (d) RuO2 in the non-faradaic region of 1.12–1.22 V vs. RHE at various scan rates. -- Figure S10. (a–c) SEM image and d) EDX spectrum of CoMoP after long term OER stability test-ing. -- Figure S11. (a–c) SEM image and d) EDX spectrum of CoMoP after long term HER stability test-ing. -- Table S1. Comparison of OER performance of CoMoP with some previously reported CoP-based catalysts in 1.0 M KOH solution. -- Table S2. Comparison of HER performance of CoMoP with some previously reported CoP-based catalysts in 1.0 M KOH solution. -- Table S3. Comparison of OWS performance of CoMoP with some previously reported CoP-based catalysts in 1.0 M KOH solution., ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya., Peer reviewed

19 pages. -- Figure S1. Synthesis scheme of Ni-2D-SA. -- Figure S2. PXRD patterns of Ni-2D-SA (black) and Ni-2D-O-SA (red). -- Figure S3. FT-IR spectra of Ni-2D-SA and Ni-2D-O-SA. -- Figure S4. chemical shift of 13C SSNMR spectra of Ni-2D-SA and Ni-2D-O-SA. -- Figure S5 SEM images of: (a) Ni-2D-O-SA, (b) Ni-2D-O-SA-CNT, (c) Ni-2D-SA-CNT. -- Figure S6. (a)-(c) HAADF-STEM images of Ni-2D-O-SA displaying the presence of atomically dispersed nickel atoms. (d) HAADF-STEM image and EDS mapping. -- Figure S7. Fourier transformed Ni K-edge EXAFS spectra of Ni-SA plotted in R-space, Fourier transformed EXAFS spectra in R-space of Ni-SA and fitted curve. -- Table S1. The Ni K-edge EXAFS fitting parameters of Ni-SA. R：bond length, CN: coordination number. -- Figure S8. Fourier transformed Ni K-edge EXAFS spectra of Ni-2D-SA plotted in R-space, Fourier transformed EXAFS spectra in R-space of Ni-SA and fitted curve. -- Table S2. The Ni K-edge EXAFS fitting parameters of Ni-2D-SA. -- Table S3. The Ni K-edge EXAFS fitting parameters of Ni-2D-O-SA. -- Figure S9. Fourier transformed Ni K-edge EXAFS spectra of Ni-2D-O-SA after immersed in KHCO3 for three days plotted in R-space, Fourier transformed EXAFS spectra in R-space of Ni-SA and fitted curve. -- Table S4. The Ni K-edge EXAFS fitting parameters of Ni-2D-O-SA-KHCO3. -- Figure S10. Pore size distribution of Ni-2D-SA and Ni-2D-O-SA powder, respectively. -- Figure S11. PXRD of Ni-2D-SA-CNT, Ni-2D-O-SA-CNT and CNT. -- Figure S12. HAADF-STEM image and EDS elemental mapping for Ni-2D-O-SA-CNT. -- Figure S13. Left panel: i-t curve on Ni-2D-O-SA-CNT at -0.9 V vs. RHE for 1h Right panel: Calibration curves for methanol (0.2 mM DMSO as internal standard). -- Figure S14. NMR spectrum of the catholyte after 1 hour of CO2 reduction on Ni-2D-O-SA-CNT. -- Figure S15. (a and b) Current densities of CO2RR for Ni-2D-O-SA-CNT and Ni-2D-SA-CNT at various potentials. (c and d) Product distribution of CO2RR for Ni-2D-O-SA-CNT and Ni-2D-SA-CNT at various potentials. -- Figure S16. (a,c) CV curves on Ni-2D-O-SA-CNT and Ni-2D-SA-CNT with different scan rates (5, 10, 20, 50, 100 mV s-1). (b, d) Current at open circuit potential (OCP) versus scan rates of different samples. The electrode area is 1 cm-2. -- Figure S17. Product distribution for Ni-2D-O-SA-CNT under Ar-saturated 0.1 M KHCO3 electrolyte at various potentials. -- Figure S18. NMR spectrum of the catholyte after 1 hour of CO2 reduction on Ni-2D-O-SA-CNT. -- Figure S19. NMR spectrum of the catholyte after 1 hour of electro-reduction under Ar environment on Ni-2D-O-SA-CNT. -- Figure S21. XPS spectra of Ni-2D-O-SA-CNT on carbon paper before and after 1 and 5 hours of CO2RR test. -- Figure S22. Product distribution of CO2RR for 2D-O-SA-CNT (without nickel) at various potential. -- Figure S23. Free-energy profiles of hydrogen evolution reaction (HER) on selected segments of Ni-2D-SA and Ni-2D-O-SA, respectively. -- Figure S24. The adsorption energy for intermediates (from CO to methanol) on selected segments of Ni-2D-SA and Ni-2D-O-SA, respectively. -- Figure S25. Free energy diagram of CO2 to CH3OH on selected segments of Ni-2D-O-SA. -- Table S5. Performance comparison of our catalysts and previous reported molecular based electrocatalysts for conversion of CO2 to methanol., ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya., Peer reviewed

22 pages. -- PDF file includes: Experimental Procedures; DFT calculations. -- Figure S1. (a,b) SEM image and EDX spectrum of Ni-MOF-1D sample. (c) High magnification STEM-HAADF image and EDX elemental mapping showing the elemental distribution in a Ni-MOF-1D sample. (d) XRD pattern of Ni-MOF-1D. -- Figure S2. High magnification HAADF-STEM images and detailed STEM-EDX elemental maps of a Ni-MOF 1D catalyst. -- Figure S3. iDPC-STEM images of Ni-MOF-1D with different magnifications. -- Figure S4. (a) XPS survey spectrum of Ni-MOF-1D. (b-d) High resolution XPS spectra of b) C 1s, c) N 1s, and d) Ni 2p. -- Table S1 Detailed EXAFS fitting model and parameters of Ni-MOF-1D. -- Figure S5. Wavelet transform (WT) analysis of (a) Ni-MOF-1D, (b) Ni foil, and (c) NiO. -- Figure S6. 1H NMR spectra of the obtained sample of Ni-MOF-1D. -- Figure S7. (a) Projected integral of the charge density in the non-periodic direction. (b) Projected integral of the charge density in the periodic direction of Ni-MOF-1D. -- Figure S8. Calculated electron localization function (ELF) of Ni-MOF-1D. -- Figure S9. (a) SEM-EDX compositional maps and (b) EDX spectra of S@Ni-MOF-1D. (c) XRD pattern of S@Ni-MOF-1D. (d) TGA profile from S@Ni-MOF-1D measured in N2 atmosphere. (e) N2 adsorption-desorption isotherms of Ni-MOF-1D and S@Ni-MOF-1D. Inset: Pore size distribution of Ni-MOF-1D and S@Ni-MOF-1D. -- Figure S10. Electrical conductivity of the two hosts tested before and after fusion with sulfur. -- Figure S11. Binding energies and adsorbed structures of LiPS on the surface of carbon calculated by DFT. -- Figure S12. Binding energies and adsorbed structures of LiPS on the surface of Ni-MOF-1D calculated by DFT. -- Figure S13. The optimized adsorption configuration of Li2S decomposition on carbon. -- Figure S14. The optimized adsorption configuration of Li2S decomposition on Ni-MOF-1D. -- Figure S15. (a) CV curve of Ni-MOF-1D as electrode measured in symmetric coin cell configuration using an electrolyte containing 1 mol L−1 LiTFSI dissolved in DOL/DME (v/v =1/1). (b) CV curves of symmetric cells from 1 to 50 cycles. (c) CV profiles of Ni-MOF-1D electrodes in symmetric cells at scan rate from 2 mV s-1 to 20 mV s-1. -- Figure S16. EIS spectra of symmetrical cells with different host materials, Ni-MOF-1D (a) and Super P (b), using an electrolyte containing 0.5 mol L-1 Li2S 6 and 1 mol L-1 LiTFSI dissolved in DOL/DME (v/v = 1/1). -- Figure S17. Onset potential for Li–S redox reactions. -- Figure S18. CV curves of S@Super P at different scan rates. -- Figure S19. First four cycles of CV curves of (a) S@Ni-MOF-1D, and (b) S@Super P performed at a scan rate of 0.1 mV s−1. -- Figure S20. Plots of CV peak current. -- Figure S21. Charge profiles of S@Ni-MOF-1D, and S@Super P electrodes showing the overpotentials for conversion between soluble LiPS and insoluble Li2S2/Li2S. --Figure S22. (a) Galvanostatic charge/discharge profiles of S@Super P electrodes at different current densities range from 0.1 C to 3 C. (b) EIS spectra of S@Super P coin cells before and after cycling. -- Figure S23. High-loading cycling performances with sulfur loadings of 7.6 mg cm-2 at 0.5 C of S@Ni-MOF-1D electrodes. -- Figure S24. (a) Galvanostatic charge/discharge profiles of S@Ni-MOF-1D at various current rates with a high sulfur loading of 4.3 mg cm−2. (b) Rate capability of S@Ni-MOF-1D cathodes loaded with 4.3 mg cm−2 of sulfur at various C rates. -- Figure S25. (a) TGA curve of a S@Ni-MOF-1D composite with a higher sulfur loading. (b) Cycling stability and Coulombic efficiency of the S@Ni-MOF-1D cathode with a higher sulfur loading at 1 C for 250 cycles. -- Table S2 Summary of recent reports on MOF-based sulfur host cathodes for LSBs., ICN2 acknowledges the support from the Severo Ochoa Programme (MINECO, Grant no. SEV-2017-0706). IREC and ICN2 are both funded by the CERCA Programme/Generalitat de Catalunya., Peer reviewed

18 pages. -- PDF file includes: Experimental Section. -- Table S1. Complete list of samples produced and characterized, including name, precursors and processing conditions. -- Figure S1. SEM images of a) ZIF-67, b) Co3O4, c) Mo-Co MOFs-1h, d) MoCoxOy-100-1h, e) Mo-Co MOFs-3h, f) MoCoxOy-100-3h, g) Mo-Co MOFs-12h, and h) MoCoxOy-100-12h. -- Figure S2. SEM images of a) Co3O4, b) MoCoxOy-50, c) MoCoxOy-100 and d) MoCoxOy-200. -- Figure S3. (a-d) TEM and (e-f) HAADF STEM images of MoCoxOy-100. -- Figure. S4. EELS chemical composition maps obtained from the red squared area of the STEM micrograph of MoCoxOy-100. Individual Mo M4,5-edges at 227 eV (red), Co L2,3-edges at 779 eV (green), O K-edge at 532 eV and C K-edge at 284 eV (grey) and composites of Co-O and Mo-Co-O. -- Figure S5. XRD patterns of a) Mo-Co MOFs produced using different stirring times, b) MoCoxOy-100 samples obtained from the annealing of Mo-Co MOFs produced with different stirring times and c) MoCoxOy-100 after different annealing temperature. -- Figure S6. XRD patterns of a) Na2MoO4-ZIF-67 and b) Na2MoO4-CoOx after 350 °C calcination. -- Figure S7. a) SEM images of Na2MoO4-ZIF-67. b-c) SEM images and d) EDX spectrum of Na2MoO4-CoOx after 350 °C calcination. -- Figure S8. a-c) SEM images and b) EDX spectrum of MoCoxOy-50 after 350 °C calcination. -- Figure S9. a-c) SEM images and d) EDX spectrum of MoCoxOy-100 after 350 °C calcination. -- Figure S10. a-c) SEM images and d) EDX spectrum of MoCoxOy-200 after 350 °C calcination. -- Figure S11. a-c) SEM images and d) EDX spectrum of MoCoxOy-100 after 450 °C calcination. -- Figure S12. a-c) SEM images and d) EDX spectrum of MoCoxOy-100 after 550 °C calcination. -- Figure S13. Pore size distribution for a) Co3O4 and b) MoCoxOy-100. -- Figure S14. a-d) Co 2p high-resolution XPS spectra of Co3O4 and MoCoxOy with different molybdenum contents. -- Figure S15. a-d) O 1s high-resolution XPS spectra of Co3O4 and MoCoxOy with different molybdenum contents. -- Table S2. Surface ratios of Co and Mo chemical states, ratio of adsorved vs. lattice oxygen, and Mo/Co ratio as obtained from the XPS analysis. -- Table S3. Comparison of OER activity of obtained catalyst. -- Figure S16. Cyclic voltammograms for a) Mo-Co MOFs; b) IrO2; c) Co3O4 and d) MoCoxOy50; e) MoCoxOy-100; f) MoCoxOy-200 in the non-faradaic region of 0.90-1.00 V vs. RHE at various scan rates. -- Table S4. Cdl and ECSAs of various catalysts. -- Figure S17. a) OER polarization curves for MoCoOx-100 annealed at different tempratures and Na2MoO4-CoOx. b) ECSA-normalized OER polarization curves for Mo-Co MOFs, IrO2, Co3O4, MoCoxOy-50, MoCoxOy-100 and MoCoxOy-200 in 1.0 M KOH. -- Figure S18. OER polarization curves of a) MoCoxOy-100 before and after 2000 cycles. b) Co3O4 at different pH values. -- Figure S19. Time-dependent concentration of Mo and Co ions dissolved in the electrolyte during of MoCoxOy-100 a 18h chronoamperometric test at 282 mV vs. RHE. -- Table S5. Comparison of OER activity of amorphous MoCoxOy-100 nanosheets with recently reported Co-based electrocatalysts in alkaline electrolyte., Peer reviewed

16 pages. -- PDF file includes: 1.Characterization. -- 2. Electrocatalysis measurement. -- 3. Photocatalytic reduction of oxygen to hydrogen peroxide. -- 4. RRDE test. -- 5. Computational method. -- 6. Apparent quantum yield (AQY) calculations. -- 7. Structural characterization. -- 8. Elemental analysis. -- 9. Band structure. -- 10. Surface area and porosity. -- 11. Calibration for H2O2 quantification. -- 12. Photocatalytic activity. -- 13. Linear sweep voltammetry. -- 14. DFT calculation results. -- 15. Reaction mechanisms., Peer reviewed

15 pages. -- PDF file includes: 1. SEM-EDS characterization. -- 2. TEM characterization. -- 3. XPS characterization. -- 4. Electrochemical measurement. -- 5. IC measurement. -- 6. DFT calculations., Peer reviewed

22 pages. -- PDF file includes: Structural characterization. -- Electrochemical Measurements. -- Faradaic efficiency (FE). -- Ionic strength compensation. -- Hypochlorite titration analysis. -- DFT Computational method. -- Figure S1 a-f) SEM images of the Mo-Co precursor. -- Figure S2 a-f) SEM images of MoN-Co2N. -- Figure S3. a-c) SEM images and d) EDS result of MoN-Co2N. -- Figure S4. a-f) TEM images of MoN-Co2N. -- Figure S5. a-c) TEM images and d-f) HAADF-STEM images of MoN-Co2N. -- Figure S6. TEM and HRTEM images of the MoN-Co2N. -- Figure S7. EELS chemical composition maps of MoN-Co2N obtained from the red squared area of the STEM micrograph. -- Figure S8. XRD patterns of MoN-Co2N, Mo-Co2N and CoxN compared with reference patterns of Co, Co4N, Co2N and MoN. -- Figure S9. a-c) SEM images and d) EDS result of Mo-Co2N. -- Figure S10. a-c) SEM images and d) EDS result of CoxN. -- Figure S11. Pore size distribution plot for MoN-Co2N and CoxN. -- Figure S12. Cyclic voltammograms for a) MoN-Co2N; b) Mo-Co2N; c) CoxN and d) Mo-Co precursors and e) IrO2 in the non-faradaic region of 1.12-1.22 V vs. RHE at various scan rates. -- Figure 13. a) N and b) Co partial and c) Total Density of states for Co2N and MoN-Co2N. -- Figure S14. The evolutions of local structural configurations for illustrating OER process of Co2N. (* represents the active site). -- Figure S15. Photograph of flasks containing seawater after adding KOH (left) and before adding KOH (right). -- Figure S16. Overall water/seawater splitting performance of MoN-Co2N ‖ MoN-Co2N and Pt/C ‖ IrO2 cells in 1 M KOH, 1 M KOH seawater, and untreated seawater. -- Figure S17. Overall water splitting performance of MoN-Co2N ‖ MoN-Co2N and Pt/C ‖ IrO2 cells in 1 M KOH seawater with and without ionic strength compensation. -- Figure S18. a) Digital photographs of the reaction and reference solutions for the iodometric titration, showing the absence of ClO− production in theº former case. b) Measured (dots) and theoretical (solid line) gaseous products by the two-electrode electrolyzer at a current of 50 mA cm-2 in 1 M KOH seawater. -- Figure S19. High-resolution XPS spectra of a) N 1s, b) Co 2p, c) Mo 3d for MoN-Co2N and MoN-Co2N after long-term reaction. -- Figure S20. a-b) TEM images, c-d) HAADF-STEM images, e-f) HRTEM of MoN-Co2N after long time reaction. -- Figure S21. EELS chemical composition maps of MoN-Co2N after long time reaction obtained from the red squared area of the STEM micrograph. Individual C K-edge at 284 eV (orange), N K-edge at 401 eV (blue), Co L2,3-edges at 779 eV (red) and Mo M4,5-edges at 227 eV (green) and composites of Co-N and Mo-N. -- Table S1. Comparison of OER activity of MoN-Co2N with recently reported nitride electrocatalysts in 1.0 M KOH electrolyte. -- Table S2. Cdl and ECSAs of various catalysts. -- Table S3. Comparison of HER performance of MoN-Co2N with recently reported nitride electrocatalysts in 1.0 M KOH electrolyte. -- Table S4 Comparison of the overall water splitting of MoN-Co2N with previously reported electrocatalysts., The development of cost-effective bifunctional catalysts for water electrolysis is both a crucial necessity and an exciting scientific challenge. Herein, a simple approach based on a metal–organic framework sacrificial template to preparing cobalt molybdenum nitride supported on nitrogen-doped carbon nanosheets is reported. The porous structure of produced composite enables fast reaction kinetics, enhanced stability, and high corrosion resistance in critical seawater conditions. The cobalt molybdenum nitride-based electrocatalyst is tested toward both oxygen evolution reaction and hydrogen evolution reaction half-reactions using the seawater electrolyte, providing excellent performances that are rationalized using density functional theory. Subsequently, the nitride composite is tested as a bifunctional catalyst for the overall splitting of KOH-treated seawater from the Mediterranean Sea. The assembled system requires overpotentials of just 1.70 V to achieve a current density of 100 mA cm–2 in 1 M KOH seawater and continuously works for over 62 h. This work demonstrates the potential of transition-metal nitrides for seawater splitting and represents a step forward toward the cost-effective implementation of this technology., Peer reviewed

11 pages. -- Figure S1. SEM image and EDS spectrum of the as-synthesized NiS NPs. -- Figure S2. NiS NPs: (a) XPS survey spectrum. (b-c) Corresponding Ni 2p3/2, and S 2p high resolution XPS spectra. -- Figure S3. Ni NPs: (a) XRD pattern. (b) Representative TEM micrograph and the corresponding size distribution. -- Figure S4. CV curves for the monometallic Ni NPs based electrode in 1 M KOH with the presence of 1 M methanol or ethanol in alkaline media at a scan rate of 50 mV s 1. -- Table S1. Fitting parameters for the Nyquist curve at 1.5 V in 1.0 M KOH with and without 1.0 M m ethanol or ethanol. -- Figure S5. Electrochemical performance dependence on alcohol concentration for Ni-based electrode in 1 M KOH electrolyte. -- Figure S6. Electrochemical activity of Ni-based electrode in 1 M KOH. -- Figure S 7 . (a) CV curves in the potential range of 0.9 1. 6 V at different scan rates . (b) Linear fitting between the peak current and scan rates from 10 to 50 mV s 1 . (c) Linear fitting between the peak current and square root of scan rates from 60 to 100 mV s 1. -- Table S2. Comparison of the alcohols oxidation performance between this work and previously reported electrocatalysts with a similar system. -- Figure S8. (a) CA test towards MOR and EOR on NiS NPs electrode over 10,000 s testing period in 1 M KOH at 1.6 V. (b) IC curve of the solution at the end of CA testing. -- Figure S9. (a) Survey XPS spectrum of the NiS-based electrode after 10,000 s testing period in 1 M KOH and 1 M ethanol at 1.6 V. (b) High-resolution Ni 2p XPS spectrum. (c) High-resolution S 2pXPS spectrum. -- Figure S10. (a) Optimized structural model of NiOOH SO 4 (b) DOS of Ni OOH and Ni OOH SO 4 regarding the Ni 3d orbitals., The electrocatalytic oxidation of alcohols is a potentially cost-effective strategy for the synthesis of valuable chemicals at the anode while simultaneously generating hydrogen at the cathode. For this approach to become commercially viable, high-activity, low-cost, and stable catalysts need to be developed. Herein, we demonstrate an electrocatalyst based on earth-abundant nickel and sulfur elements. Experimental investigations reveal the produced NiS displays excellent electrocatalytic performance associated with a higher electrochemical surface area (ECSA) and the presence of sulfate ions on the formed NiOOH surface in basic media. The current densities reached for the oxidation of ethanol and methanol at 1.6 V vs reversible hydrogen electrode (RHE) are up to 175.5 and 145.1 mA cm–2, respectively. At these high current densities, the Faradaic efficiency of methanol to formate conversion is 98% and that of ethanol to acetate is 81%. Density functional theory calculations demonstrate the presence of the generated sulfate groups to modify the electronic properties of the NiOOH surface, improving electroconductivity and electron transfer. Besides, calculations are used to determine the reaction energy barriers, revealing the dehydrogenation of ethoxy groups to be more favorable than that of methoxy on the catalyst surface, which explains the highest current densities obtained for ethanol oxidation., Peer reviewed