Atomic layer deposition of cobalt phosphate thin films for the oxygen evolution reaction

Electrodeposited cobalt phosphate has been reported as a valid alternative to noble metals as an electrocatalyst for the Oxygen Evolution Reaction (OER). In parallel, Atomic Layer Deposition (ALD) is increasingly being used in (photo)electrocatalytic applications. In this contribution we report on the electrocatalytic activity towards OER of ALD-prepared cobalt phosphate thin films. The selected ALD approach enables tuning of the Co-to-P atomic ratio, which is found to significantly affect the activity of the prepared electrocatalyst. Specifically, concurrently with a Co-to-P ratio increase from 1.6 to 1.9, the current density for OER increases from 1.77 mA/cm² at 1.8 V vs. RHE (Reversible Hydrogen Electrode) to 2.89 mA/cm² at 1.8 V vs. RHE. Moreover the sample with a Co-to-P ratio of 1.9 has superior performance when compared to electrodeposited cobalt phosphate thin films reported in the literature.