Conductive CuCo-Based Bimetal Organic Framework for Efficient Hydrogen Evolution.

Abstract

Metal-organic frameworks (MOFs) with intrinsically porous structures and well-dispersed metal sites are promising candidates for electrocatalysis; however, the catalytic efficiencies of most MOFs are significantly limited by their impertinent adsorption/desorption energy of intermediates formed during electrocatalysis and very low electrical conductivity. Herein, Co is introduced into conductive Cu-catecholate (Cu-CAT) nanorod arrays directly grown on a flexible carbon cloth for hydrogen evolution reaction (HER). Electrochemical results show that the Co-incorporated Cu-CAT nanorod arrays only need 52 and 143 mV overpotentials to drive a current density of 10 mA cm^-2 in alkaline and neutral media for HER, respectively, much lower than most of the reported non-noble metal-based electrocatalysts and comparable to the benchmark Pt/C electrocatalyst. Density functional theory calculations show that the introduction of Co can optimize the adsorption energy of hydrogen (ΔG_H* ) of Cu sites, almost close to that of Pt (111). Furthermore, the adsorption energy of water ( <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>Δ</mi> <msub><mi>E</mi> <mrow><msub><mi>H</mi> <mn>2</mn></msub> <mi>O</mi></mrow> </msub> </mrow> </math> ) of Co sites in the CuCo-CAT is significantly lower than that of Cu sites upon coupling Cu with Co, effectively accelerating the Volmer step in the HER process. The findings, synergistic effect of bimetals, open a new avenue for the rational design of highly efficient MOF-based electrocatalysts.