Chitosan Hydrogel Derived Carbon Foam with Typical Transition-Metal Catalysts for Efficient Water Splitting

Abstract Herein, we present a stepwise approach for constructing 3-dimensional porous carbon foam pretreated via glutaraldehyde cross-linking and decorated with highly dispersed molybdenum carbide (CF-Glu-Mo) or Co-doped FeNi carbonate hydroxide (CF-Glu-CoFeNi), which is structurally derived from the initial chitosan hydrogel. The as-prepared CF-Glu-Mo and CF-Glu-CoFeNi can act as mono-functional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. In 1.0 M KOH, CF-Glu-Mo exhibits a small overpotential of 88 mV with a low Tafel slope of 56 mV dec-1 under the working condition of 10 mA cm-2 for HER, and CF-Glu-CoFeNi requires an overpotential of 290 mV for OER to reach a current density of 50 mA cm-2, accompanied by a low Tafel slope of 115 mV dec-1. In this case, these integrated electrodes derived from the robust interconnection between the electrocatalyst and the chitosan hydrogel derived carbon foam make the whole water decomposition behavior more direct and efficient, which is reasonably attributed to hierarchically porous nanostructures and intrinsically high conductivity. The full electrolyzer assembled with carbon cloth (CC) of CF-Glu-Mo/CC||CF-Glu-CoFeNi/CC can drive full alkaline water splitting by applying a voltage of 1.65 V at a catalytic current of 10 mA cm-2 for 24 h. Meanwhile, this work provides a feasible approach for the development of efficient water splitting electrocatalysts through the rational design and regulation of heterogeneous interfaces and nanostructures.