Assembly Engineering of Rh Atoms on CoAl-Layered Double Hydroxide Nanosheets for Boosting Alkaline Water Splitting

Layered double hydroxides (LDHs), especially Co-based LDHs, are regarded as a class of promising electrocatalysts toward overall water splitting, due to their good performance in oxygen evolution reaction (OER). However, inferior activity toward hydrogen evolution reaction (HER) hinders their scale-up applications. Here, a one-step hydrothermal strategy is proposed to fabricate 3D self-supported Rh-incorporated CoAl LDH (Rh/CoAl LDH) nanosheet arrays as bifunctional catalysts for overall water splitting. The thickness and lateral size of CoAl LDHs depend strongly on the introduced content of Rh atoms. Importantly, Rh incorporation distorts the local atomic arrangement owing to different atom sizes on the CoAl laminate. The strong interaction between Rh atoms and CoAl LDHs dramatically boosts the HER activity by facilitating HER kinetics and improves the OER performance simultaneously. The Rh/CoAl-300 LDH electrode with optimized composition only requires an overpotential of 71 mV to reach 10 mA/cm2 for HER and 390 mV to achieve 100 mA/cm2 for OER. The alkaline electrolyzer assembled by bifunctional Rh/CoAl-300 LDH electrodes only needs a cell voltage of 1.54 V at an overall water splitting of 10 mA/cm2.