Coordination Engineering of Carbon Dots and Mn in Co-Based Phosphides for Highly Efficient Seawater Splitting at Ampere-Level Current Density.

Abstract

Direct electrolysis of seawater to generate hydrogen is an attractive approach for storing renewable energy. However, direct seawater splitting suffers from low current density and limited operating stability, which severely hinders its industrialization. Herein, a promising strategy is reported to obtain a nano needle-like array catalyst-CDs-Mn-CoxP on nickel foam, in which the Mn─O─C bond tightly binds Mn, Carbon dots (CDs), and CoxP together. The coordination engineering of CDs and Mn not only effectively regulates the electronic structure of CoxP, but also endows the as-prepared catalyst with selectivity and marked long-term stability at ampere-level current density. Low overpotentials of 208 and 447mV are required to achieve 1000mA cm-2 for hydrogen evolution reaction (HER) and Oxygen evolution reaction (OER) in simulated seawater, respectively. Cell potentials of 1.78 and 1.86V are needed to reach 500 and 1000mA cm-2 in alkaline seawater along with excellent durability for 350h. DFT studies have verified that the introduction of Mn and CDs effectively shifts the d-band center of Co-3d toward higher energy, thereby strengthening the adsorption of intermediates and enhancing the catalytic activity. This study sheds light on the development of highly effective and stable catalysts for large-scale seawater electrolysis.