Highly active bimetallic noble metal alloys electrocatalyst

Abstract

As Hydrogen fuel is looking to be a strong contender for an alternative source of fuel in the future, an efficient catalyst has to be found to aid in the water splitting process. In this report, thin film electrocatalysts of Rh, Rh-Pt and Rh-Ir were fabricated by using Atomic Layer Deposition (ALD) on a glassy carbon (GCE) substrate.

The composition of each electrode was assessed using field emission scanning electron microscope with energy dispersive x-ray analysis (FESEM-EDX), x-ray reflectometry (XRR) and x-ray photoelectron spectroscopy (XPS).

Linear Sweep Voltammetry (LSV) and chronopotentiometry (CP) were used to evaluate the performance of each fabricated electrocatalyst. Overpotential values were obtained from the LSV curve. Tafel plots were obtained from the LSV curve, and exchange current densities were calculated from the Tafel plot. A good electrocatalyst will have low overpotential, low Tafel slope, high exchange current density and good stability.

The results showed that Rh-Ir had surprisingly low overpotentials of -0.148 V on average, with a standard deviation of 0.0189 V. Rh-Ir also had high exchange current densities of 6.92 mA/cm2, with a standard deviation of 1.97 mA/cm2. However, its Tafel slope was high and the Rh samples had lower Tafel slopes of -479.8 mV/dec. The OER was not very good for all the samples. Not all the samples were able to achieve overpotential values at J = 0.1 mA/cm2. It should also be noted that all exchange current densities calculated for OER are much smaller compared to the HER exchange current densities.

This report presents the work on the process of fabricating thin films of Rh, Rh-Pt and Rh-Ir on GCEs by using a novel ALD. The fabricated thin films on GCEs will then be used as an electrocatalyst for water splitting. Based on the findings, the three fabricated electrodes show low overpotentials and Tafel slopes in HER and OER. They also have decent exchange current densities and stabilities.