Research Highlights

2D Cocatalysts

With the booming interest towards the utilization of solar energy for renewable energy, in article number 2111875, Wee-Jun Ong and co-workers review the recent progress and prospects on 2D/2D cocatalyst/g-C₃N₄ photocatalysts for solar-to-chemical conversion and environmental purification. Interfacing 2D/2D heterojunctions has been touted as an effective strategy to harness electron-hole redox centers that will prolong the lifetime of photocatalysts and improve the overall performance in energy and environmental science.

The solar-driven conversion of water and CO2 into value-added fuels has the potential to help us achieve net-zero carbon emissions. Among the semiconductor photocatalysts, ZnIn2S4 has hit the limelight due to its narrow bandgap and visible-light-responsive. Wee-Jun Ong et al. provide in-depth insights into the structure-performance relation of ZnIn2S4-based nanomaterials toward light-driven hydrogen evolution, overall water splitting and CO2 reduction.

Solar-powered chemistry

Solar-driven CO2-to-fuel conversion has become a promising avenue towards tackling the exponential rise in global CO2 emissions. As a class of metal-free nanomaterial, graphitic carbon nitride (g-C3N4) has been widely studied for solar-driven CO2 reduction with its allotropes (e.g. C3N5. C2N) rising in popularity recently. External-field assisted methods have incited much interest due to their synergistic contribution to the photochemical CO2 reduction reaction. The rise of viable solar technology paves a sustainable alternative to the current fuel source to close the carbon cycle and achieve a circular carbon economy.

Point-Defect Engineering

Solar energy is an abundant source of renewable energy, which can be harnessed via photocatalysis. Of which, point-defect engineering is a robust strategy to tune physico-chemical properties of graphitic carbon nitride toward enhanced photocatalytic H2O splitting, CO2 and N2 reduction. A comprehensive review is presented by Wee-Jun Ong and co-workers in article number 2006851.

The development of single-atom catalysts (SACs) for electrochemical devices is at the forefront of energy conversion. The comparison of stability, activity, and selectivity among various single atoms is one of the main research focuses of SACs. However, in-depth understanding of the role played by single-atom coordination atoms in catalysis is lacking. This cover art presents a a graphene-like boron–carbon-nitride (BCN) monolayer as the support of single metal atom for robust nitrogen reduction to ammonia. Therefore, this work may provide a research avenue for designing multi-active sites anchoring single atoms and substrate innate atoms based on mechanistic insights to guide future studies on electrocatalytic nitrogen reduction reactions.

2D/2D Heterostructured Photocatalysts

This cover art presents the latest insights into the interplay of 2D/2D heterojunctions and charge carrier dynamics toward ameliorated photo-driven water splitting, CO2 reduction, and N2 fixation, and discuss challenges and prospects in the field.

The cover art features a fluorescence-responsive self-healing hydrogel with a triple network structure, which exhibits a 100% recovery in tensile strength after healing in air for 30 s and a 90% recovery in tensile strength after healing in water for 60 s. Furthermore, this material can resist a rotation of 1800° without breaking at the healed site. With these sensing and self-healing abilities all in one, self-healing luminescent materials could be applied to tissue engineering, photoresponsive biosensors, flexible light guiding devices, structural health monitoring, etc.

The cover art features a scheme of artificial photosynthetic solar energy conversion. Inspired by the natural photosynthesis in plants, Wee-Jun Ong and co-workers have synthesized noble-metal-free iron phosphide (FeP) nanodot-modified porous graphitic carbon nitride (g-C₃N₄) as the photocatalyst for solar-to-hydrogen generation. Our experimental and computational results demonstrate that the FeP/g-C₃N₄ heterostructure composite can effectively boost photocatalytic hydrogen evolution under visible light without the presence of Pt noble metals. Overall, this work not only paves a new path in the engineering of monodispersed FeP-decorated g-C₃N₄ 0D/2D robust nanoarchitectures, but also elucidates potential insights for the utilization of noble-metal-free FeP nanodots as remarkable co-catalysts for superior photocatalytic H₂ evolution.

On page 18479, Wee-Jun Ong and co-workers systematically investigated high quality transition‐metal carbonitrides M₃CN (MXene) for electrocatalytic hydrogen generation using well‐defined density functional theory (DFT) calculations. In addition, only Ti₃CNO₂ and Nb₃CNO₂ have the potential to be HER active catalysts. Overall, this work presents in‐depth investigations for transition‐metal carbonitrides (MXene) and opens up new designs for robust metal carbonitrides as noble‐metal‐free cocatalysts for highly efficient and low‐cost MXene‐based nanocomposites for water splitting applications.

On page 21941, Wee-Jun Ong and co-workers systematically investigated single transition metal atoms anchored on graphitic carbon nitride (g-C₃N₄) with nitrogen vacancies (TM@NVs-g-C₃N₄), acting as electrocatalysts for N₂ reduction by means of density functional theory (DFT) calculations. Overall, this work exemplifies the in-depth investigations of different single TM atoms, including the coordination number and binding mode, which are essential to lay the groundwork for the advancement of single atom catalysis toward practical implementation.

Featured in Nanowerk

Photocatalysis, which is the mimicry of the natural photosynthesis, is a game-changing breakthrough for the conversion of solar energy to chemical fuels. As presented by Wee-Jun Ong and co-workers in article number 1700251, benefiting from the natural sheet-like structure in g-C₃N₄, precious-metal-free 1D Co₂P nanorods are hybridized with 2D g-C₃N₄ to form intact 1D/2D heterointerfaces for H₂ evolution without Pt as noble-metal co-catalysts. By tailoring 1D and 2D nanohybrids, this leads to unprecedented properties toward remarkable enhancement of solar H₂ production technology.

On page 9, Ong and co-workers provided a critical review on the state-of-the-art engineering of efficient photocatalysts for dinitrogen (N₂) fixation toward NH₃ synthesis. Strenuous efforts have been devoted to modifying the intrinsic properties of semiconductors (i.e. poor electron transport, rapid electron–hole recombination and sluggish reaction kinetics), including nanoarchitecture design, crystal facet engineering, doping and heterostructuring. In this review, the most recent advancements in understanding the charge carrier kinetics of photocatalysts with respect to charge transfer, migration and separation, which are of fundamental significance to photocatalytic N₂ fixation, are presented. As such, it is anticipated that this review will shed new light on photocatalytic N₂ fixation and NH₃ synthesis and will also provide a blueprint for further investigations and momentous breakthroughs in next-generation catalyst design.

Featured on Phys.org (Media News)

Despite the progress made in photocatalytic CO₂ reduction, the understanding of fundamental nanoscience is still limited. On page 1673, Ong and co-workers for the first time demonstrated the successful construction of metal-free zero-dimensional/two-dimensional (0D/2D) carbon nanodot (CND)-hybridized protonated g-C₃N₄ (pCN) (CND/pCN) heterojunction photocatalysts by means of electrostatic attraction. In this work, a combination of experimental and density functional theory (DFT) investigations is performed in addressing the gaps in the knowledge about CND/pCN photocatalysts, and to advance the CO₂ reduction process to an industrial scale. The efficient shuttling of electrons from the conduction band of pCN to CNDs hampers the recombination of electron–hole pairs. This significantly increased the probability of free charge carriers reducing CO₂ to CH₄ and CO. Overall, this study highlights the significance of comprehending the charge carrier dynamics of the CND/pCN hybrid nanocomposites, in order to ammeliorate solar energy conversion.