Directly preparing well-dispersed ultra-hydrophilic NiFeP nanoparticle/Mxene complexes from spent electroless Ni plating solution as efficient hydrogen evolution catalysts

A novel approach is proposed to prepare well-dispersed ultra-hydrophilic NiFeP nanoparticle/Mxene complex by recovering Ni, P, and organic acid from spent electroless Ni-plating solution. The mechanism of NiP-based nanoparticle formation and size regulation during the hydrothermal process is analyzed. Ni2+ chelated with sodium citrate in the electroless Ni plating effluent anchors on the Ti3C2 surface with -OH functional groups by chemical reaction and charge adsorption owing to Mxene surface negativity. The as-prepared ultrafine NiFeP nanodots are connected with alkali-induced Ti3C2 Mxene nanosheets, which possess ultra-hydrophilic performance and rapid H2 bubble desorption behavior. The introduction of alkali-induced Ti3C2 MXene as a substrate controls particle agglomeration in the hydrothermal crystallization process and achieves perfect dispersed distribution of NiFeP nanoparticles to further increase the specific surface area of catalyst. Consequently, the NiFeP/Ti3C2 nanohybrid catalyst exhibits outstanding hydrogen evolution reaction (HER) electrocatalyst performance as a result, with an overpotential of 122 mV at 10 mA cm−2, quick reaction kinetics of 68 mV dec−1, and strong long-term stability over 24 h in 1 M KOH. This research develops a strategy for directly preparing high-value catalyst materialization from spent electroless Ni-plating solution.