Yolk–shell structured microspheres consisting of CoO/CoP hetero-interfaced nanocomposites as highly active hydrogen evolution reaction electrocatalysts for AEM electrolyzer stacks

Abstract

An anion exchange membrane water electrolyzer (AEM electrolyzer) is an advanced technology for converting electrical energy into hydrogen energy with high efficiency and low cost. However, its advantages are diminished by significant voltage losses due to insufficient catalytic activity. To address this issue, yolk–shell structured microspheres consisting of CoO/CoP hetero-interfaced nanocomposites (YS-CoO/CoP) have been developed as highly active hydrogen evolution reaction (HER) electrocatalysts, which exhibited and an over potential −126 mV at −10 mA cm⁻² and was applied in an AEM electrolyzer. The yolk–shell structure improves ion and gas transport, reducing mass transport losses, while enhancing HER activity resulting from electron redistribution at the CoO/CoP interface. The AEM electrolyzer equipped with YS-CoO/CoP for the HER and NiFe-LDH for the OER shows reduced activation and mass transport losses, achieving a high current density of 0.6 A cm⁻² at 1.8 V_cell. Additionally, a 3-cell AEM electrolyzer stack equipped with non-platinum group metal (non-PGM) electrocatalysts for both the OER and HER demonstrates high performance.