Harvesting ionic power from a neutralization reaction through a heterogeneous graphene oxide membrane

Nanofluidics is a system of fluid transport limited to a nano-confined space, including the transport of ions and molecules. The use of intelligent nanofluidics has shown great potential in energy conversion. However, ion transport is hindered by homogeneous membranes with uniform charge distribution and concentration polarization, which often leads to an undesirable power conversion performance. Here, we demonstrate the feasibility of a neutralization reaction-enhanced energy conversion process based on heterogeneous graphene oxide (GO) nanofluidics with a bipolar structure. The asymmetric charge distribution inherent to the heterogeneous nanofluidics facilitates a complementary two-way ion diffusion process, which in turn promotes efficient charge separation and superposed ionic diffusion. An output power density of up to 29.58 W m^-2 is achieved with 0.1 M HCl/NaOH as the acid-base pair (ABP), which is about 712% and 117% higher than using symmetric unipolar pGO and nGO membranes. Both experiments and theoretical simulations indicate that the tunable asymmetric heterostructure contributes to regulating diffusion-based ion transport and enhancing the ion flux. This work not only establishes a significant paradigm for the utilization of chemical reactions within nanofluidic systems but also opens up new avenues for ground-breaking discoveries in the fields of chemistry, nanotechnology, and materials science.