Solar-Driven Polyvinyl Alcohol Remediation: Black Phosphorus Quantum Dot Sensitized g-C3N4 Photocatalyst Vs. H2 Evolution in Photocatalytic Fuel Cells

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In response to polyvinyl alcohol (PVA) waste pollution, we developed a composite photocatalyst by sensitizing g-C3N4 with black phosphorus quantum dots (BPQDs) using a simple mechanical stirring technique. Both g-C3N4 and BPQDs are inorganic semiconductors, enabling efficient photoinduced charge transfer. Leveraging the adjacency of C, N, and P elements in the periodic table facilitated the formation of P-N or P-C bonds, resulting in uniform BPQD decoration on two-dimensional layered g-C3N4, with an average size of 2.2 nm. Under solar light simulator irradiation for 20 minutes, the composite photocatalyst exhibited significantly enhanced photocatalytic activity, increasing PVA degradation efficiency from 27.1% (pure g-C3N4) to 85.9%. Experimental observations and theoretical calculations suggest the establishment of a Z-scheme route at the g-C3N4/BPQDs interface, facilitating photoinduced electron transfer from g-C3N4 to BPQDs, leading to augmented carrier generation and separation, reduced charge-transfer resistance, and accelerated PVA degradation. The proposed composite photocatalyst holds promise in addressing PVA pollution and promoting environmental sustainability.Additionally, in a dual-chamber photocatalytic fuel cell setup, simultaneous degradation of PVA and hydrogen evolution were achieved, employing commercial P25 as the photoanode and Ag@Fe2O3 nanoparticles as the cathode. Moreover, the feasibility of a Fenton-like reaction at the cathode, utilizing Fe2+ ions and pumped O2, was demonstrated. The effects of different cathode materials, PVA types, and pH values on device performance were assessed, with quenching tests highlighting the pivotal roles of h+ and OH· radicals in PVA degradation. The device's long-term stability was established through cycling experiments.