Rational design of carbon nitride photoelectrodes with high activity toward organic oxidations Carolina Pulignani 1 , Camilo A. Mesa 1 , Sam A. J. Hillman 2 , Taylor Uekert 3 , Sixto Giménez 1 , James R. Durrant 2 , Erwin Reisner 1,3 1 University of Cambridge, UK, 2 Universitat Jaume I (UJI), Spain, 3 Imperial College London, UK Carbon nitride (CN x ), an inexpensive, non-toxic, noble metal-free polymeric semiconductor, has attracted much recent attention for its use as a sustainable light absorber in artificialphotosynthesis and organic photocatalysis. The use of this material as a photoelectrocatalyst and its use in photoelectrochemical cells could result in cheap and sustainable devices capable of storing solar energy in chemical bonds. Although the performances of CN x suspensions are already approaching practical levels, the photocurrent density reported for carbon nitride photoelectrodes is still limited by some of itsintrinsic characteristics (i.e., low conductivity, high recombination rates, low surface area, and weak particle adhesion). [1] Moreover, current reports lack from a basic understanding of the intrinsic processes happening within the CN x films, preventing the rational design of more competitive photoelectrodes. [2] In this poster, we report a facile and reproducible method to synthesize versatile and high-performance cyanamide-functionalized carbon nitride ( NCN CN x )photoanodes based on a rational design.The co-deposition of NCN CN x with indium tin oxide (ITO) nanoparticles onto a 1.8 Å thick alumina-coated FTO glass substrate led to a record 1.4 ± 0.2 mA cm –2 at 1.23 V vs RHE with a very low onset of –0.4 V vs RHE, incident photon-to-current efficiency (IPCE) of60.0 ± 3.6%, and Faradaic efficiencies ≥ 95% for the selective oxidation of 4-methylbenzyl alcohol to the corresponding aldehyde. These performances are new benchmarks in developing carbon nitride photoelectrodes (c.f., 0.67 mA cm –2 using a sacrificial hole scavenger as the previous record). [3] Moreover, we proved the versatility towardsthe oxidation of various alcohols such as glycerol, the main by-product of biodiesel production, ethylene glycol, model molecule for plastic photoreforming; and simple alcohols accessible from plant biomass, such as methanol and ethanol. Furthermore, we have carried out detailed photoelectrochemical, photo-induced absorption, transient absorption spectroscopy, transient photocurrent, and photoelectrochemical impedance spectroscopy measurements to rationalize and provide a well-supported explanation for the role of each component in achieving these excellent charge separation properties, and high hole-extraction efficiency. More specifically, the ITO nanoparticlesact as a conductive binder and improve electron extraction from the CN x , which otherwise remain trapped in the organic semiconductor, while thealumina underlayer increases the electrical contact between the ITO nanoparticles and the FTO-coated electrode. References 1. Volokh, M.; Peng, G.; Barrio, J.; Shalom, M. Angew. Chemie - Int. Ed. 2019, 58, 6138–6151[2] 2. Godin, R.; Wang, Y.; Zwijnenburg, M. A.; Tang, J.; Durrant, J. R. J. Am. Chem. Soc. 2017, 139, 5216–5224[3] 3. Peng, G; Volokh, M.; Tzadikov, J.; Sun, J.; Shalom, M. Adv. Energy Mater. 2018, 8, 1–7
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