Self-assembly of functionalized Echinops-like Rh porous nanostructure electrocatalysts for highly efficient seawater splitting

Abstract

Although water electrolysis provides a promising technology for global hydrogen economics, highly efficient electrocatalysts are required to boost the sluggish kinetics of both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) under neutral conditions. Herein, we synthesized novel polyethyleneimine (PEI) functionalized Echinops-like Rh porous nanostructures (Echinops-like Rh PNNSs) by a solvothermal method, which originated from the self-assembly of Rh two-dimensional (2D) sub-nanoflakes with 1.2 nm thickness. As a good electron donor, −NH₂ on PEI could modulate the electronic structure of Echinops-like Rh PNNSs, reducing the adsorption energy of H₂O on the surface of Echinops-like Rh PNNSs. Meanwhile, −NH₂ groups could specifically enrich H₂O molecules under neutral conditions, which facilitates water splitting. The as-synthesized Echinops-like Rh PNNSs exhibit high HER activity with ultralow overpotential, low Tafel slope, and excellent stability. Moreover, the Echinops-like Rh PNNSs also showed an enhanced OER activity than commercial RuO₂ with a small overpotential of 79.5 mV at 10 mA cm⁻² in neutral media. When using Echinops-like Rh PNNSs as both anode and cathode catalysts for overall seawater splitting, a cell voltage of only 1.61 V is needed for generating 10 mA cm⁻² current density, greatly boosting the efficiency of seawater splitting.