Controlled Synthesis of MoNi₄ Ultrathin Nanosheet Arrays as an Efficient Bifunctional Electrocatalyst for Urea-Assisted Hydrogen Production

Abstract

The utilization of water electrolysis as a technology for industrial hydrogen production is considered highly appealing. Currently, the sluggish anodic oxygen evolution reaction (OER), which involves a four-electron transfer process, hampers the overall efficiency of water splitting. The coupling of urea electrocatalysis with the hydrogen evolution reaction (HER) holds significant promise in achieving energy-efficient hydrogen production. Here, we present a study showcasing the in situ synthesis of arrays consisting of ultrathin MoNi 4 nanosheets on a Ni foam (NF) substrate (MoNi 4 /NF). The catalyst exhibits high bifunctional activity due to its excellent intrinsic activity, increased exposure of active sites, and favorable morphology and structure of the electrode material. Specifically, overpotentials as low as 146 mV and 1.42 V are sufficient to drive a current density of 100 mA cm −2 for the HER and urea oxidation reaction (UOR), respectively. Moreover, the utilization of optimized MoNi 4 /NF as a dual-electrode catalyst enables the provision of a current density of 100 mA cm −2 for hybrid water splitting when operating at a cell voltage of 1.54 V. This study presents a novel concept for the advancement of effective and enduring bifunctional electrocatalysts capable of facilitating both the HER and the UOR.