Modulation of oxygen vacancies in NiFe layered double hydroxides through dual-doping with Mo/Cr cations for efficient seawater hydrogen production

Abstract

Seawater splitting to produce hydrogen holds promise for renewable energy but faces challenges from chloride ions, causing electrode corrosion and competition between chlorine oxidation reaction (ClOR) and oxygen evolution reaction (OER). Therefore, it is crucial to develop highly efficient and stable electrocatalysts for seawater splitting. Here, we employ a dual-doping strategy of Mo/Cr cations and a sulfuration approach to fabricate the S-MoCr-NiFe@NF bifunctional catalyst with a 3D nano-flower structure. The S-MoCr-NiFe@NF catalyst exhibits remarkable catalytic performance for the oxygen evolution reaction (OER) in 1.0 M KOH + 0.5 M NaCl and 1.0 M KOH + Seawater, achieving current densities of 10 mA cm⁻² at low overpotentials of 116 and 141 mV, respectively. Furthermore, it was demonstrated that the S-MoCr-NiFe@NF catalyst exhibited remarkable performance in alkaline overall seawater splitting, requiring only 1.48 and 1.57 V to achieve current densities of 10 mA cm⁻² in 1.0 M KOH + 0.5 M NaCl and 1.0 M KOH + Seawater, respectively. The in-situ Raman and DFT calculations confirm Ni as the primary active sites, reducing the energy barrier of the rate-determining step and enhancing OER performance. This study will offer a viable approach to developing and creating highly effective bifunctional catalysts for seawater splitting.