Laser-engineered nanocomposite electrodes for hydrogen generation and in situ sewage wastewater treatment

Abstract

This work demonstrates a sustainable approach to produce clean hydrogen by utilizing sewage wastewater as an electrolyte. This strategy aims to eliminate the requirement of conventional purified water required as an electrolyte source. Here, a Mo-doped Ni-based metal–organic framework precursor is carbonized over Ni foam using CO₂ laser to synthesize a bimetallic composite with conductive and porous carbon serving as an electrocatalyst. The Mo dopant concentration during synthesis was systematically varied to optimize the electronic structure of the Ni centre to enhance its electrocatalytic activity for the hydrogen evolution reaction. The laser-annealed Ni–Mo-based electrocatalyst obtained from the optimized Mo doping exhibited a low overpotential of 132 mV with a Tafel slope of 126 mV dec⁻¹ in alkaline sewage water. Interestingly, the Ca and Mg salts present in the sewage electrolyte are electro-precipitated during the run, resulting in simultaneous cathode scaling and water softening along with hydrogen production. This approach also presents a potential route to extract valuable minerals, adding a resource-recovery element to the process. Therefore, the simultaneous hydrogen production with integrated wastewater remediation demonstrates a promising route towards a circular economy framework.