In situ regulating the interfacial work function of Ag doped Ni(OH)2 via trace of Fe2+ for efficient water splitting

Abstract

Traditional approaches for tuning the water electrolysis performance of catalysts through manipulating their work function (WF) have primarily focused on the design of pre-catalysts prior to electrochemical test. Herein, an in situ interfacial WF modulation concept has been developed to synthesize the Fe modified nickel-based hydroxide electrocatalyst with enhanced OER (named as 0.168-FeO-Ag-Ni(OH)2/NF) and HER (0.168-FeH-Ag-Ni(OH)2/NF) activity. The modulator is trace amounts of Fe2+ in 1 M KOH, while the support comprises silver-modified nickel hydroxide, in which the Ag possesses a valence catalysis effect on Ni or Fe sites. Under optimized Fe2+ content, the deposition of Fe facilitates the release of the WF of Ag-Ni(OH)2/NF and accelerates the electron transfer between the catalyst and reaction intermediates. Meanwhile, the charge transfer from Fe to Ni sites coupled with the blue shift of d-band promote the adsorption of water molecules and the desorption of hydrogen protons, thereby accelerating the hydrogen evolution reaction kinetics. Consequently, the OER and HER activity of 0.168-FeO-Ag-Ni(OH)2/NF and 0.168-FeH-Ag-Ni(OH)2/NF enhanced 4.31 and 2.48 times, respectively. Notably, compared with Ag-Ni(OH)2/NF(+)//Ag-Ni(OH)2/NF(−), at a high current density of 1000 mA cm−2, the potential for energy consumption reduction of 0.168-FeO-Ag-Ni(OH)2/NF(+)//0.168-FeH-Ag-Ni(OH)2/NF(−) couple is at least 6 %, which endows it a promising application prospect in the actual electrolytic water system in the future.