An efficient monolithic green reactor for Photo(electro)catalysis: Hybridizing g-C3N4 with Fe/Ni nanoparticles on wood sponge for water oxidation, N2 and CO2 photofixation, and interfacial solar steam generation

In this work, we present a novel multifunctional photo(electro)catalytic system by innovatively hybridizing graphitic carbon nitride (g-C3N4) with Fe/Ni (FeNi) nanoparticles (NPs) and integrating them onto a biodegradable wood sponge (WS) substrate, resulting in an effective green monolithic reactor. To the best of our knowledge, this is the first report combining g-C3N4 with FeNi NPs in various heterojunction structure supported on a naturally porous WS framework. This unique architecture significantly enhances visible light harvesting, interfacial charge separation, and mass transport. The layered g-C3N4/FeNi structure achieves a photocurrent density of 0.31 mA cm−2 at 1.23 V vs. RHE, six times higher than pristine g-C3N4. The WS monolithic substrate, featuring a high surface area and abundant open channels, enables efficient solar-driven N2 and CO2 photoreduction. The resulting WS/g-C3N4 (CN)/FeNi system exhibits superior photofixation performance, with NH3, CO, and CH3OH with evolution rates of 2600, 302, and 70 μmol g−1 h−1, respectively. FeNi NPs serve as active sites to facilitate molecular sorption and boost interfacial electron transfer. Also, WS/CN/FeNi photoabsorber demonstrates excellent interfacial solar steam generation, reaching a water evaporation flux of 1.43 kg m−2 h−1 under 1 sun (1 kW m−2). The device demonstrates excellent stability and reusability over multiple cycles, maintaining consistent performance under simulated sunlight irradiation. The integrated design offers a promising strategy for solar energy conversion, utilization, and storage, contributing to the development of sustainable energy technologies.