Cobalt-Loaded Carbon\nNitride Demonstrates Enhanced\nPhotocatalytic Production of H<sub>2</sub> from Lignocellulosic Biomass\nComponents

Photocatalytic production of hydrogen (H<sub>2</sub>)\nfrom biomass\nis a promising avenue for advancing sustainable energy generation.\nWe prepared carbon nitride (CN<sub><i>x</i></sub>) with\ncobalt (Co) as an oxidation cocatalyst (denoted CN<sub><i>x</i></sub>/Co) to improve photocatalytic H<sub>2</sub> production through\nphotoreforming components of lignocellulosic biomass under visual\nlight irradiation. CN<sub><i>x</i></sub>/Co was synthesized\nby loading Co onto preformed CN<sub><i>x</i></sub> through\na straightforward thermal deposition. The thermal loading of Co at\n450 °C led to the formation of a mixed valence CoO<sub><i>x</i></sub>, which shifted Co<sup>2+</sup> character to Co<sup>3+</sup> over the course of the hydrogen evolution reaction (HER).\nCompared to CN<sub><i>x</i></sub> without Co, our materials\nwith 0.3 and 0.6 wt % Co demonstrate twice the apparent quantum yield\n(AQY) for H<sub>2</sub> production under irradiation at 405 nm using\nglucose as a sacrificial electron donor (3.0% and 2.8%, respectively,\nvs 1.4%). Time-resolved spectroscopic investigations indicate that\nthe Co extracts charges in the subnanosecond time scale and promotes\nthe formation of beneficial long-lived charges. Impressively, some\nphotocatalytic activity is observed when using the robust polymers\nof cellulose and lignin as the oxidation substrates (0.2 and 0.1%\nAQY, respectively). The ability to oxidize abundant biomass without\nextensive prepreparation is promising for waste upcycling applications.