Nickel catalysed and decorated CO2 laser induced graphene from bio-waste-derived thermoset polymer as a high-performance catalyst for oxygen evolution reaction

Abstract

In this work, we examine carbonization of natural product derived thermoset polymer by CO2 laser-assisted direct-write transient pyrolysis process without and with the addition of nickel salt for possible catalytic intervention. We find that nickel indeed plays an interesting and crucial role in significantly enhancing the graphene content in the laser processed sample (Ni-LIG) retaining its few monolayer character. The unique and significant advantages of laser induced transient pyrolysis process are: a) it is a direct write process enabling in-process functionality patterning, if needed, b) it is highly energy economic because energy is localized and directed to the desired process zone, c) being a transient process it can be implemented under ambient conditions, and d) it creates distinctly different microstructure as compared to furnace annealing. It was further observed that upon incorporation of the Ni(CH3COO)2.4H2O salt in the polymer the LIG process reduces it to Ni (111), which in turn catalyses the nucleation process and lowers the activation barrier for graphene formation by annealing the defects. Moreover, due to the very low lattice mismatch between Ni (111) and graphene facilitates its high growth quality. The concurrent decoration of Ni/NiO on graphene is also shown to promote water dissociation as well as adsorption of water oxidation intermediates. This leads to an impressive value of the overpotential for oxygen evolution reaction (OER) at 10 mA/cm2 of only 290 mV in 1 M KOH. Additionally, the catalytic capacity and structure remain stable after 30 h of continuous work in 1 M KOH.