Surface-Dependent Hydrogen Evolution Activity of Copper Foil

Abstract

Single-crystal planes are ideal platforms for catalytic research. In this work, rolled copper foils with predominantly (220) planes were used as the starting material. By using temperature gradient annealing, which caused grain recrystallization in the foils, they were transformed to those with (200) planes. In acidic solution, the overpotential of such a foil (10 mA cm^-2) was found to be 136 mV lower than that of a similar rolled copper foil. The calculation results show that hollow sites formed on the (200) plane have the highest hydrogen adsorption energy and are active centers for hydrogen evolution. Thus, this work clarifies the catalytic activity of specific sites on the copper surface and demonstrates the critical role of surface engineering in designing catalytic properties.

Keywords: copper foils; crystal planes control; hydrogen evolution; temperature gradient annealing.

Scheme 1

Preparation of copper foils. (a,c) are schematic diagrams of rolling process and temperature gradient annealing process, respectively; (b,d) are photographs of S-Cu, IA-Cu, and CA-Cu, respectively.

Figure 1

Characterization of samples S-Cu, IA-Cu, and CA-Cu. (a) XRD patterns and SEM images of samples S-Cu (b), IA-Cu (c), and CA-Cu (d).

Figure 2

HER performance of samples S-Cu, IA-Cu, and CA-Cu. (a) LSV curves, (b) overpotentials at 10 mA cm⁻², (c) Tafel curves, (d) Nyquist plots.

Figure 3

CV curves of samples S-Cu (a), IA-Cu (b), and CA-Cu (c). (d) Non-Faradaic current density (Δj) as a function of scan rate (mV s⁻¹) of the electrode (slopes corresponding to the DLC values).

Figure 4

(a) LSV curves normalized by ECSA values, (b) DLC values of samples S-Cu, IA-Cu, and CA-Cu.

Figure 5

Adsorption energy of hydrogen on top, bridge, and hole sites of Cu (111), (220), and (200) planes. (a) Atomic models of hydrogen adsorption on Cu top, bridge, and hollow sites. (b) Free energy diagram, where * denotes the active site of the catalyst. (c) ΔG_H values for the same sites.