Dynamic competitive adsorption mechanism was constructed by Mo incorporation to achieve the high activity and durability electrolysis of saline-alkali water for hydrogen production

• Mo/(CoFeNi) 3 S 2 with crystal-amorphous biphase supernanometer structure was synthesized. • Dynamic competitive adsorption mechanism was constructed by Mo incorporation. • Regulation of adsorption mechanism inhibits Cl - corrosion and keeps the OER activity. • High selectivity and efficiency direct electrolysis of saline-alkali water was achieved. The development of highly selective and bifunctional catalysts for direct electrolysis of saline-alkali water is a major challenge, which can inhibit the corrosion of the active site on the catalyst by Cl - . In this paper, we successfully synthesized the Mo/(CoFeNi) 3 S 2 catalyst with crystal-amorphous dual-phase supra-nano (SNDP) structure on nickel foam (NF) by a simple two-step hydrothermal method, which can be used for the direct electrolysis of saline-alkali water to produce hydrogen and oxygen at industrial current density. Electrochemical contrast test and in situ characterization test show that the introduction of Mo clusters is crucial for the improvement of the intrinsic activity and durability of catalysts. Theoretical calculation results show that the introduction of Mo clusters changes the dominant adsorption ion of Ni site from Cl - to OH – , and the competitive adsorption between the Cl - and OH – result in the preferential adsorption of OH – at the Ni site and Cl - at the Mo site, which can prevent Cl - from attacking the active sites for oxygen evolution during the electrolysis of saline-alkali water. At an industrial current density of 500 mA cm −2 , the performance of Mo/(CoFeNi) 3 S 2 is maintained for 1000 h without significant degradation, which proves the feasibility of direct electrolytic saline-alkali water to produce hydrogen and oxygen.