First Authors: Huaxing Li, Rongjie Li, and Heng Li
Corresponding Authors: Gang Liu, Xuebo Chen, Lirong Zheng, and Xiaoying Qi
DOI: 10.1016/j.apcatb.2026.126534
This study combines single-atom catalysis with a Schottky junction. Atomically dispersed Rh atoms were successfully anchored on a 2D/2D Ti₃C₂/g-C₃N₄ Schottky junction through ball milling and photoreduction. The Rh single atoms not only act as efficient electron-transfer channels but also downshift the p-band centers of coordinated N and O atoms, optimizing the Gibbs free energy of hydrogen adsorption and enabling efficient visible-light-driven photocatalytic hydrogen evolution.
In February 2026, Applied Catalysis B: Environment and Energy published online new work from a research team including the National Center for Nanoscience and Technology on photocatalytic hydrogen production. A Ti₃C₂/g-C₃N₄ Schottky-junction photocatalyst modified with isolated Rh atoms achieved a visible-light-driven hydrogen-evolution rate of 1195.5 μmol h⁻¹ g⁻¹.
Graphitic carbon nitride (g-C₃N₄) is an important semiconductor for photocatalytic hydrogen evolution because of its high stability, low toxicity, and visible-light response. Its efficiency, however, is limited by low electrical conductivity and slow surface-reaction kinetics. Constructing a Schottky junction promotes charge separation, but further accelerating charge-transfer dynamics and optimizing the intrinsic reaction rate at active sites remain essential for improving overall performance.
The researchers used a Perfectlight Microsolar 300 Xenon Lamp for visible-light-driven photocatalytic hydrogen-evolution experiments. Stable and controllable irradiation conditions help ensure reproducible catalytic-evaluation data.
Bulk g-C₃N₄ was first converted into ultrathin nanosheets, which were then ball-milled with Ti₃C₂ nanosheets to construct a 2D/2D heterointerface. Finally, Rh single atoms were photoreduced and deposited on the Ti₃C₂/CN surface under visible light. HAADF-STEM reveals numerous uniformly dispersed isolated Rh atoms, while EDX elemental mapping confirms successful formation of the ternary composite.
Rh K-edge XANES and FT-EXAFS show that Rh is present in a partially oxidized positive state and atomically dispersed in Rh–N₄ and Rh–O₃ coordination environments. XPS reveals spontaneous electron transfer from CN to Ti₃C₂, a characteristic signature of Schottky-junction formation.
In situ illuminated XPS shows that photogenerated electrons are driven toward Ti₃C₂. DMPO–•O₂⁻ EPR measurements demonstrate that the Schottky junction and Rh single atoms synergistically improve charge-separation efficiency. UV–Vis diffuse-reflectance spectroscopy shows a redshift of the absorption edge to 466 nm, corresponding to a band gap of 2.66 eV. DFT calculations and charge-density-difference analysis further support suppression of electron backflow by the Schottky barrier.
0.25-Rh/TCCN-3 achieves a hydrogen-evolution rate of 1195.5 μmol h⁻¹ g⁻¹, which is 102 times that of pristine CN and 11 times that of TCCN-3. No obvious activity loss is observed after 16 h of cycling. Transient photocurrent, EIS, and PL measurements collectively confirm more efficient charge separation and a lower carrier-recombination rate.
TCCN-3 exhibits an interfacial electron-transfer process with a time constant of approximately 33.5 ps. In 0.25-Rh/TCCN-3, an additional ultrafast 1.9 ps process is observed and assigned to electron injection from the Schottky junction into the Rh single atoms. The Rh atoms therefore function as “electron pumps” that efficiently extract and transport charge.
Rh is coordinated in an Rh–N₄ configuration on the CN(001) surface. After Rh modification, the p-band center of the coordinated N atoms shifts downward from −5.34 to −6.60 eV, improving ΔGH* at the N site from −1.39 to −0.46 eV and lowering the reaction-energy barrier.
Rh adopts an Rh–O₃ coordination configuration. The p-band center of the coordinated O atoms shifts downward from −3.72 to −4.35 eV, while ΔGH* improves from −0.52 to −0.04 eV, approaching the ideal value. Following visible-light excitation of CN, electrons migrate toward Ti₃C₂ under the built-in electric field and are then injected ultrafast through Rh–O₃ and Rh–N₄ channels into Rh sites, where they reduce protons to H₂.
This work constructs a Ti₃C₂/g-C₃N₄ Schottky-junction photocatalyst modified with Rh single atoms, delivering a hydrogen-evolution rate 102 times that of pristine g-C₃N₄. The Schottky junction provides the driving force for charge separation, while Rh–N₄ and Rh–O₃ coordination environments establish rapid electron-transfer channels. The Rh single atoms also regulate the p-band centers of active sites and the adsorption–desorption behavior of reaction intermediates, offering a new strategy for designing artificial photosynthetic systems.
Gang Liu is a researcher whose work focuses on hierarchical nanocomposites, two-dimensional layered materials, metal nanoparticles and single atoms, photocatalytic hydrogen production, photocatalytic CO₂ reduction, and the adsorption and degradation of environmental organic pollutants.
Huaxing Li, Rongjie Li, Heng Li, Xidong Zhang, Jiaguo Yu, Gang Liu, Lirong Zheng, Xiaoying Qi, and Xuebo Chen. “Single Rh Atoms on Ti₃C₂/g-C₃N₄ Schottky Junction: Downshifting p-Band Centers and Accelerating Charge Dynamics for Enhanced Photocatalytic H₂ Evolution.” Applied Catalysis B: Environment and Energy, 2026, 388: 126534.
