Urea-oxidation-assisted electrochemical water splitting for hydrogen production on a bifunctional heterostructure transition metal phosphides combining metal-organic frameworks

Chunchao Chen; Liujun Jin; Lei Hu; Tingyu Zhang; Jinghui He; Peiyang Gu; Qingfeng Xu; Jianmei Lu

doi:10.1016/j.jcis.2022.08.127

Urea-oxidation-assisted electrochemical water splitting for hydrogen production on a bifunctional heterostructure transition metal phosphides combining metal-organic frameworks

J Colloid Interface Sci. 2022 Dec 15;628(Pt B):1008-1018. doi: 10.1016/j.jcis.2022.08.127. Epub 2022 Aug 24.

Authors

Chunchao Chen¹, Liujun Jin¹, Lei Hu¹, Tingyu Zhang¹, Jinghui He¹, Peiyang Gu¹, Qingfeng Xu², Jianmei Lu³

Affiliations

¹ College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, Jiangsu 215123, China.
² College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, Jiangsu 215123, China. Electronic address: xuqingfeng@suda.edu.cn.
³ College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, Jiangsu 215123, China. Electronic address: lujm@suda.edu.cn.

PMID: 36049277
DOI: 10.1016/j.jcis.2022.08.127

Abstract

Electrocatalyzed urea-assisted wastewater splitting is a promising approach for sustainable hydrogen production. However, the lack of cost-efficient electrocatalysts hinders its practical application. Herein, bimetal phosphide (NiCoP_x) nanowire arrays decorated with ultrathin NiFeCo metal-organic framework (NiFeCo-MOF) nanosheets on porous nickel foam (NF) were designed for urea-assisted wastewater splitting. The core-shell NiCoP_x@NiFeCo-MOF hybrids were prepared via successive hydrothermal, gas-phase phosphorization and hydrothermal strategies. Encouragingly, the novel NiCoP_x@NiFeCo-MOF/NF electrode served as an excellent bifunctional electrocatalyst for both the cathodic hydrogen evolution reaction (HER) and the anodic urea oxidation reaction (UOR) in urea-assisted water splitting, which merely required an overpotential of 44 mV to deliver a current density of 10 mA cm^-2 for HER and a voltage of 1.37 V to deliver a current density of 100 mA cm^-2 for UOR in 1.0 M KOH + 0.5 M urea. Benefiting from the highly exposed electroactive sites in exquisite three-dimensional (3D) hierarchical structure, multicomponent synergistic effect, accelerated electron transfer, easy electrolyte access and diffusion of released gas bubbles, the as-fabricated NiCoP_x@NiFeCo-MOF/NF exhibited outstanding electrocatalytic performance. The mechanism of water splitting was elucidated by density functional theory calculations. Interestingly, NiFeCo-MOF possessed optimized COO* adsorption ability on Ni sites that were beneficial to UOR intermediates. More significantly, this work paves the way for the design and fabrication of bifunctional electrocatalysts for urea-containing wastewater treatment and sustainable hydrogen production.

Keywords: Bifunctional catalyst; Cobalt phosphide; Hydrogen evolution reaction; Metal-organic framework; Urea electrolysis.