LAUSR

Abstract Regulating chemical bonds to balance the adsorption and disassociation of water molecules on catalyst surfaces is crucial for overall water splitting in alkaline solution. Here we report a facile strategy for designing Ni2W4C-W3C Janus structures with abundant Ni–W metallic bonds on surfaces through interfacial engineering. Inserting Ni atoms into the W3C crystals in reaction progress generates a new Ni2W4C phase, making the inert W atoms in W3C be active sites in Ni2W4C for overall water splitting. The Ni2W4C-W3C/carbon nanofibers (Ni2W4C-W3C/CNFs) require overpotentials of 63 mV to reach 10 mA cm−2 for hydrogen evolution reaction (HER) and 270 mV to reach 30 mA cm−2 for oxygen evolution reaction (OER) in alkaline electrolyte, respectively. When utilized as both cathode and anode in alkaline solution for overall water splitting, cell voltages of 1.55 and 1.87 V are needed to reach 10 and 100 mA cm−2, respectively. Density functional theory (DFT) results indicate that the strong interactions between Ni and W increase the local electronic states of W atoms. The Ni2W4C provides active sites for cleaving H–OH bonds, and the W3C facilitates the combination of Hads intermediates into H2 molecules. The in situ electrochemical-Raman results demonstrate that the strong absorption ability for hydroxyl and water molecules and further demonstrate that W atoms are the real active sites.