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

18 pages. -- Figure S1. (a) Bright field STEM image of the synthesized AuNRs. (b) Bright field STEM image of the AuNR@SiO2 after the first silica-shell coating. -- Figure S2. (a) STEM micrographs of synthesized AuNR@UiO-66 composite before (left) and after (right) exposure to iodine gas at 75 °C for 3 hours. Note that the AuNRs were etched after having been exposed to the iodine. (b) STEM micrographs of the AuNR@SiO2@UiO-66 composite before (left) and after (right) exposure to iodine at 75 °C for 96 hours, confirming the stability of the silica-coated AuNRs. Scale bar: 500 nm. -- Figure S3. N2-sorption isotherm measurements at 77 K, and corresponding BET plots, for UiO-66 microbeads (a) and AuNR@SiO2@UiO-66 microbeads (b). -- Table S1. Summary of the maximum temperatures reached by each studied material upon irradiation with near-infrared lasers of different intensities. -- Figure S4. (a) Plot of time vs. temperature for AuNR@SiO2@UiO-66 microbeads irradiated for 1 minute with near infrared light at an intensity of 224 mW cm-2. (b) Thermal imaging of the UiO-66 (leftmost) when irradiated at 1000 mW cm-2, and AuNR@SiO2@UiO-66 microbeads when irradiated with an intensity of 52 mW cm-2 (left), 224 mW cm-2 (middle) and 1000 mW cm-2 (right). -- Figure S5. Thermogravimetric analysis curves for pristine UiO-66 microbeads (blue), iodineloaded UiO-66 microbeads (black), and iodine-loaded AuNR@SiO2@UiO-66 microbeads (red). -- Figure S6. (a) PXRD spectra of pristine UiO-66 (black), pristine AuNR@SiO2@UiO-66 (red), UiO-66 after desorption of iodine (blue), and AuNR@SiO2@UiO-66 after desorption of iodine (green). (b) HAADF-STEM micrograph of AuNR@SiO2@UiO-66 after 96-hour exposure to iodine at 75 °C. Scale bar: 100 nm. -- Figure S7. Release of iodine from I2@UiO-66 microbeads (black) and I2@AuNR@SiO2@UiO-66 microbeads (red), without any laser irradiation. Inset: zoomed section of graph. -- Figure S8. FE-SEM micrographs of cross-sections of the composite films containing AuNR@SiO2@UiO-66 microbeads at 0% (a), 8% (b), 25% (c) and 46 (d)% (w/w). -- Figure S9. TGA curves of the iodine-loaded composite films containing AuNR@SiO2@UiO- 66 microbeads at 0% (black), 8% (red), 25% (blue) and 46% (green) (w/w). -- Figure S10. Iodine release over time from the composite films containing AuNR@SiO2@UiO-66 microbeads at 46% (a) and 25% (b) (w/w), without any laser irradiation. -- Figure S11 (a) Stepwise release of iodine from a composite film containing I2@AuNR@SiO2@UiO-66 microbeads at 25% (w/w) irradiated with NIR light at 224 mW cm-2 and subjected to on/off switching. (b) Zoom on the stepwise release after its stabilization at the fifteenth cycle. -- Figure S12. Growth-inhibition zones induced by I2@UiO-66 microbeads (a, b) and I2@AuNR@SiO2@UiO-66 microbeads (c, d) against E. coli (a, c) or S. aureus (b, d) cultures, either after near-infrared light irradiation (left) or without irradiation (right). Ø: diameter of growth-inhibition zone. Disc diameter: 6 mm. -- Figure S13. Growth-inhibition zones induced by square sections of composite films containing iodine-loaded AuNR@SiO2@UiO-66 at 8% (a), 25% (b) and 46% (c) (w/w), against E. coli cultures, either after near-infrared light irradiation (left) or without irradiation (right). Ø: diameter of growth-inhibition zone. Film size: 1 cm2. Values are the average of at least five replicates ± standard deviation. -- Table S2. Growth-inhibition of composite films prepared at different iodine-containing microbead-loadings (8%, 25% or 46%) and tested on E. coli cultures., ICN2 is supported by the Severo Ochoa program from the Spanish MINECO (Grant No. SEV-2017-0706), Peer reviewed

11 pages. -- PDF files includes: Experimental section; Photocatalytic experiment; Synthesis of GDY powder; Preparation of CuO/GDY/TiO2 and GDY/TiO2; Preparation of Pt loaded TiO2, tables and figures. -- Figure S1. The prepared GDY powder by using deprotection-free method. -- Table S1. Screening of catalysts and solvents for the direct coupling reaction of HEB-TMS. + entry 15 was performed under Ar conditions. -- Figure S2. GC-MS spectra of the DMF solution after reaction (balck line) and the standard curve of the corresponding compound (red line). -- Figure S3. ICP-Mass results for content of Cu in the prepared CuO/GDY samples. -- Figure S4. Low- and high-magnification SEM images of the prepared CuO/GDY samples. -- Figure S5. 1*1*1 unit crystal model of CuO and atomic supercell model illustration of the CuO nanoparticle oriented as in TEM images. -- Table S2. Comparison between the experimental and the theoretical bulk plane spacing distances and angles between planes. -- Figure S6. High-resolution XPS spectra of Si in GDY. -- Table S3. The atomic percentage of different elements in pure GDY. -- Figure S7. XRD spectra of TiO2 and CuO/GDY/TiO2 with different content. -- Figure S8. (a) Raman spectra and (b) enlarged spectra of TiO2 and CuO/GDY/TiO2 with different content. - -Figure S9. (a) the full XPS spectra of TiO2 and CuO/GDY/TiO2; (b) high-resolution XPS spectra of Cu in CuO/GDY/TiO2. -- Figure S10. UV-Vis spectra of TiO2 and CuO/GDY/TiO2 with different content. -- Figure S11. photocurrent test of CuO/GDY/TiO2, GDY/TiO2, CNT/TiO2 and GR/TiO2. -- Figure S12. Tauc plot of the prepared GDY powder. -- Figure S13. Valence band spectra of the prepared GDY powder by XPS. -- Figure S14. (a) High-resolution XPS spectra of Cu in CuO/GDY/TiO2 before and after photocatalysis; (b) fitting of Cu in in CuO/GDY/TiO2 after photocatalysis. In comparison, the satellite observed for Cu 2p (corresponding to Cu2+) is significantly reduced after illumination. -- Figure S15. The proposed photocatalytic mechanism of the CuO/GDY/TiO2 photocatalysts., 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

26 pages. -- PDF file includes: Materials and methods; XAFS Measurements; XAFS Analysis and Results; Synthesis Methods: Preparation of IRMOF-3; Preparation of ZIF-8; Preparation of Fe-IRMOF-3 and Fe-ZIF-8; Preparation of Disperse Fe-N-C (denoted as O-Fe-N-C and Fe-N-C); Preparation of O-Fe-N-C-Acid; Ink Preparation; Electrochemical Measurement; Calculation Method; DFT Calculations. -- Figures and tables., ICN2 acknowledges funding from Generalitat de Catalunya 2017 SGR 327.ICN2 was supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706)., 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

62 pages. -- PDF file includes: 1. Experimental section. -- Figure S1. XRD patterns of pure ZIF-67 (a), Co(OH)2 (b) and Co3O4 (c). -- Figure S2. SEM images of Co3O4 single-shelled nanocages and EDS chemical mapping. -- Figure S3. SEM images of and EDS chemical mapping of CoP-HS (a); CoP2-HS (b); CoP3-HS (c). -- Figure S4. Nitrogen absorption–desorption isotherms and pore size distributions of three cobalt phosphides, CoP-HS (a); CoP2-HS (b); CoP3-HS (c). -- Figure S5. XPS spectra of the XPS full scan for CoP-HS, CoP2-HS and CoP3-HS. -- Figure S6. The CV curves of CoP-HS, CoP2-HS, and CoP3-HS obtained at the 1st (a), 3rd (b), 5th (c), and 10th (d) cycles at a scan rate of 10 mV/s in a 1.0 M KOH solution. -- Figure S7. The OER activities of CoP-HS, CoP2-HS and CoP3-HS were tested by both forward and reverse scan. -- Figure S8. (a) The CV of the CoPx. (b) The double layer capacitance (CDL) was determined as the half of the slope from the plot of the capacitive current vs. scan rate plot. -- Figure S9. Chronopotentiometry responses of activity stabilized CoPx in 1.0 M KOH in the catalytic turnover region. -- Figure S10. (a-c) OER LSV curves with (red) and without (blue) 100% iR drop correction. (d) Corresponding Tafel lines. -- Figure S11. SEM images of CoP-HS (a), CoP2-HS (b) and CoP3-HS (c) single-shelled nanocages after 100 h OER stability measurement. (d) The changed ratio of Co:P before and after stability test. -- Figure S12.SEM of post-OER CoP (a) before HCl wash, (b) after HCl washed. -- Figure S13. The LSV curves of CoP-HS, CoP2-HS, CoP3-HS, Co3O4-HS and Co(OH)2-HS measured in 1.0 M KOH solution toward OER at a scan rate 10 mV/s after activation by 50 CV cycles between 0.0 V and 0.85 V (vs. Hg/HgO) at a scan rate 50 mV/s. -- Figure S14. (a) The LSV curves of carbon paper measured in 1.0 M KOH toward HER at scan rate 10 mV/s. (b) The data of CoP-HS, CoP2-HS and CoP3-HS test in 1.0 M KOH. -- Figure S15. Chronopotentiometry responses of activity stabilized CoPx in 1.0 M KOH in the catalytic turnover region. -- Figure S16. (a-c) HER LSV curves with (red) and without (blue) 100% iR drop correction. (d) Corresponding Tafel lines. -- Figure S17. The CV curves of CoP-HS, CoP2-HS and CoP3-HS measured in 1.0 M KOH solution for 1st (a), 3rd (b), 5th (c), and 10th (d) cycles at a scan rate 10 mV/s. -- Figure S18. (a) The XPS spectra, and (b) the SEM image and EDS chemical mapping of CoP-HS after 100 h HER stability measurement in 1 M KOH. -- Figure S19. TEM images of CoP-HS after HER stability test (a). Elements mapping and SAED of CoP-HS after HER stability test (b-f). -- Figure S20. (a) The LSV curves of CoP-HS, CoP2-HS, CoP3-HS and Pt/C measured in 0.5 M H2SO4 toward HER at scan rate 10 mV/s. (b) The corresponding Tafel plots for the samples in 0.5 M H2SO4. (c) Nyquist plots of CoP-HS, CoP2-HS, CoP3-HS in 0.5 M H2SO4. (All the tests were taken on carbon paper). -- Figure S21. (a) The LSV curves of carbon paper measured in 0.5 M H2SO4 toward HER at scan rate 10 mV/s. (b) The data of CoP-HS, CoP2-HS and CoP3-HS test in 0.5 M H2SO4. -- Figure S22. The CV curves of CoP-HS, CoP2-HS and CoP3-HS measured in 0.5 M H2SO4 solution for 1st (a), 3rd (b), 5th (c), and 10th (d) cycles at a scan rate 10 mV/s. -- Figure S23. (a) The chronopotentiometry curve of CoP at the current density of -20 mA cm-2 for 100 h in 0.5 M H2SO4. (b) The SEM image and EDS chemical mapping (d) of CoP single-shelled nanocages after 100 h HER stability measurement. -- Figure S24. Overall water splitting activities of CoP||CoP and Pt/C||IrO2. -- Figure S25. (a, b, c, d, e, f) Corresponding levels of oxygen and hydrogen gas generated at 0 s, 200 s, 400 s, 600 s, 800 s, 1000 s. -- Figure S26. Optimized configuration of CoP-HS adsorbed with H. -- Figure S27. Optimized configuration of CoP2-HS adsorbed with H. -- Figure S28. Optimized configurations of CoP3-HS adsorbed with H. -- Figure S29. HER free energy changes of CoP-HS, CoP2-HS and CoP3-HS at P-sites and Co-site. in 0.5 M H2SO4. (c) P(2p) XPS spectra of CoP-HS after 100 h HER stability. -- Figure S30. The normalized LSV curves of CoP-HS, CoP2-HS, and CoP3-HS. -- Figure S31. The correlation between the HER free energy changes based on Co-sites of CoPx-HS and the normalized overpotential as well as Tafel slope measurement. -- Table S1. Elemental composition of Co and P in the different cobalt phosphides. -- Table S2. Comparison of the alkaline OER efficiency of those cobalt phosphides with other reported advanced cathodic materials. -- Table S3. Comparison of the alkaline HER efficiency of this CoP with other reported advanced cathodic materials. -- Table S4. Comparison of the acidic HER efficiency of this CoP with other reported advanced cathodic materials. -- Table S5. Comparison of the alkaline overall water-splitting efficiency of this CoP with other reported advanced bifunctional catalysts., 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