Enhancing deep visible-light photoelectrocatalysis with a single solid-state synthesis: Carbon nitride/TiO2 heterointerface.

Visible-light responsive, stable, and abundant absorbers are required for the rapid integration of green, clean, and renewable technologies in a circular economy. Photoactive solid-solid heterojunctions enable multiple charge pathways, inhibiting recombination through efficient charge transfer across the interface. This study spotlights the physico-chemical synergy between titanium dioxide (TiO2) anatase and carbon nitride (CN) to form a hybrid material. The CN(10%)-TiO2(90%) hybrid outperforms TiO2 and CN references and literature homologs in four photo and photoelectrocatalytic reactions. CN-TiO2 achieved a four-fold increase in benzylamine conversion, with photooxidation conversion rates of 51, 97, and 100 % at 625, 535, and 465 nm, respectively. The associated energy transfer mechanism was elucidated. In photoelectrochemistry, CN-TiO2 exhibited 23 % photoactivity of the full-spectrum measurement when using a 410 nm filter. Our findings demonstrate that CN-TiO2 displayed a band gap of 2.9 eV, evidencing TiO2 photosensitization attributed to enhanced charge transfer at the heterointerface boundaries via staggered heterojunction type II.

Electrostatic [FeFe]-hydrogenase-carbon nitride assemblies for efficient solar hydrogen production.

The assembly of semiconductors as light absorbers and enzymes as redox catalysts offers a promising approach for sustainable chemical synthesis driven by light. However, achieving the rational design of such semi-artificial systems requires a comprehensive understanding of the abiotic-biotic interface, which poses significant challenges. In this study, we demonstrate an electrostatic interaction strategy to interface negatively charged cyanamide modified graphitic carbon nitride (NCNCNX) with an [FeFe]-hydrogenase possessing a positive surface charge around the distal FeS cluster responsible for electron uptake into the enzyme. The strong electrostatic attraction enables efficient solar hydrogen (H2) production via direct interfacial electron transfer (DET), achieving a turnover frequency (TOF) of 18 669 h-1 (4 h) and a turnover number (TON) of 198 125 (24 h). Interfacial characterizations, including quartz crystal microbalance (QCM), photoelectrochemical impedance spectroscopy (PEIS), intensity-modulated photovoltage spectroscopy (IMVS), and transient photocurrent spectroscopy (TPC) have been conducted on the semi-artificial carbon nitride-enzyme system to provide a comprehensive understanding for the future development of photocatalytic hybrid assemblies.

Rational Design of Carbon Nitride Photoelectrodes with High Activity Toward Organic Oxidations.

Carbon nitride (CNx ) is a light-absorber with excellent performance in photocatalytic suspension systems, but the activity of CNx photoelectrodes has remained low. Here, cyanamide-functionalized CNx (NCN CNx ) was co-deposited with ITO nanoparticles on a 1.8 Šthick alumina-coated FTO electrode. Transient absorption spectroscopy and impedance measurements support that ITO acts as a conductive binder and improves electron extraction from the NCN CNx , whilst the alumina underlayer reduces recombination losses between the ITO and the FTO glass. The Al2 O3 |ITO : NCN CNx film displays a benchmark performance for CNx -based photoanodes with an onset of -0.4 V vs a reversible hydrogen electrode (RHE), and 1.4±0.2 mA cm-2 at 1.23 V vs RHE during AM1.5G irradiation for the selective oxidation of 4-methylbenzyl alcohol. This assembly strategy will improve the exploration of CNx in fundamental and applied photoelectrochemical (PEC) studies.