Binary Cooperative Thermal Treatment of Cellulose and MoS₂ for Preparation of Sustainable Paper-Based Electrochemical Devices for Hydrogen Evolution

The simple, fast, scalable, and integrative preparation of sustainable electrodes using earth-abundant materials toward energy applications is a long-standing challenge. In this work, we attempted to achieve such features by developing a binary cooperative thermal process using cellulose sheets and molybdenum disulfide (MoS₂) toward hydrogen evolution reaction (HER). The thermal process converts cellulose into a highly conductive hydrophobic carbon-based material while generating chemical defects on MoS₂. The latter is of fundamental importance to improve the catalytic activity for HER through activating the well-known inert MoS₂ basal planes. Thermal desulfurization was confirmed by X-ray photoelectron spectroscopy, Kelvin probe force microscopy, Raman spectroscopy and energy-dispersive X-ray spectroscopy. Interestingly, a desulfurization gradient was observed at the MoS₂ particles, where the edges are more defective than the basal planes. The resulting defect-like MoS₂ particles are highly active toward HER. In addition, the porosity of paper enables simple filtration of catalysts and the possibility to tune electrochemically active surface area by simply adding isopropanol before the electrolysis. Finally, we showed an ultrafast coating method using a commercial MoS₂ spray on sheets of paper that enables H₂ bubble generation at specific regions of the electrode. The overpotential (η) positively shifted more than 300 mV when compared with non- treated MoS₂, reaching η = 240 mV to obtain 10 mA cm^-2 of HER current density.