Bowei Zhang1 Shan Hu1

1, Iowa State University, Ames, Iowa, United States

To address increasing environmental and energy concerns, generating clean-energy fuel via a sustainable route is highly desirable. Hydrogen production from water splitting is one of the most promising technologies for meeting this target. The key to industrial application of water splitting is the design of efficient, robust, and cost-efficient catalysts as the electrodes.

As electrocatalysis reactions are surface processes, the activity of an electrocatalyst is usually dependent on the amount of accessible surface-active sites, the facileness of mass transport to/from the surface, and the electrical conductivity of the catalyst.1 Metal-organic frameworks (MOFs) provide an ideal platform for designing promising catalysts because of their high porosity and diverse nanostructures and compositions.2 However, one of the challenges of using MOFs for electrocatalysis is the very small pore size (usually within few nanometers) of bulk MOF materials, which inhibits the effective mass transport of electrolyte to the active sites and the diffusion of products, leading to impeded electrode performance. Despite the great promise of MOF electrocatalyst, significant research effort is still needed to overcome the inherit disadvantages of MOF.

Herein, we synthesized self-supported Co-based MOF nanosheets on carbon cloth and converted it to sponge-like Co-Ni hydroxide (Co-Ni-OH) by Ni salt etching method and then phosphorized the obtained product at low-temperature. Finally, the obtained sponge-like Co-Ni phosphide was converted into corresponding hydroxide (Co-Ni-OH-D) by linear scanning voltammetry scans in alkaline. The as-synthesized Co-Ni-OH-D is structurally different from the precursor Co-Ni-OH and cannot be directly synthesized with the method for growing Co-Ni-OH. The sponge-like Co-Ni-OH-D provided abundant meso-/micro-porosity for prompting the reaction rate. Co-Ni-OH-D electrode exhibits excellent electrocatalysis activities toward water splitting. This work provides a general method for deriving efficient catalyst from MOF.

References: (1) J. Duan, et al. Nat. Commun. 8 (2017). (2) G. Cai, et al. Chem 2.6 (2017) 791-802.