Tissue paper-derived porous carbon encapsulated transition metal nanoparticles as advanced non-precious catalysts: Carbon-shell influence on the electrocatalytic behaviour

Porous carbon encapsulated non-precious metal nanocatalysts have recently opened the ways towards the development of high-performance water remediation and energy conversion technologies. Herein, we report a facile, scalable and green synthetic methodology to fabricate porous carbon encapsulated transition metal nanocatalysts (M@TP: M = Cu, Ni, Fe and Co) using commercial tissue paper. The morphology, crystalline structure, chemical composition and textural properties of the M@TP nanocatalysts were thoroughly characterized. The catalytic activity of the M@TP nanocatalysts was investigated for the degradation of Congo red (CR) via peroxymonosulfate activation. Co@TP-6 was found to be the most active catalyst allowing 97.68% degradation in 30 min with a higher rate constant of 0.109 min^-1. The nanocatalysts also displayed a carbon shell thickness-dependent electrocatalytic hydrogen evolution reaction (HER) activity, most likely due to the shielding effect of the carbon layers over the electron transfer (ET) processes at the metal core/carbon interfaces. Remarkably, the Ni@TP-6 electrocatalyst, with the smaller carbon shell thickness, showed the best electrocatalytic performance. They delivered an ultralow onset potential of -30 mV vs RHE, an overpotential of 105 mV at a current density of 10 mA·cm^-2 and an excellent electrochemical stability to keep the 92% of the initial current applied after 25000 s, which is comparable with the HER activity of the state-of-the-art Ni-based catalysts.