Nickel-Zinc Hydroxide-Orchestrated Nitrogen-Doped Carbon/ Bismuth Vanadate Nanosheet Aerogels Power 24 Hour Solar-to-Hydrogen Systems
Abstract
Ring-opening polymerization (ROP) affords a powerful driving force for the large-scale assembly of polymer precursors and photo-induced charge channels via incorporating aromatic repeat units into the polymer main chain. Herein, a range of monolithic aerogels were constructed based on the polymerization of a branched benzoxazine monomer, in which few-layer BiVO4 nanosheets were embedded within nitrogen self-doped carbon aerogels (NC). The resultant hierarchically structured NC/BiVO4 aerogels exhibited high specific surface area, ultralow density, and high electrical conductivity. The polymerization of the branched benzoxazine monomer facilitated direct and tight contact between NC and BiVO4, contributing to the generation of structural disorder (as evidenced by 19F Δδ and X-ray Pair Distribution Function (PDF) analysis) and thus enabling more efficient storage of reactive ions in the photocatalytic system. As a proof-of-concept demonstration, we assembled an integrated system where solar cells incorporating the 3D monolithic NC/BiVO4 aerogels charged rechargeable Ni-Zn batteries utilizing a zinc-doped nickel-based cathode (Ni0.95Zn0.05(OH)2.0), achieving a stable output voltage of 1.89 V. The solar-charged batteries enabled the system to operate not only during the day (via direct solar power) but also at night (via energy released from the batteries), resulting in a 24 h continuous, fully solar-powered uninterrupted overall water-splitting system.