Review—Origin and Promotional Effects of Plasmonics in Photocatalysis

Plasmonic effects including near-field coupling, light scattering, guided mode through surface plasmon polaritons (SPPs), Förster resonant energy transfer (FRET), and thermoplasmonics are extensively used for harnessing inexhaustible solar energy for photovoltaics and photocatalysis. Recently, plasmonic hot carrier-driven photocatalysis has received additional attention thanks to its specific selectivity in the catalytic conversion of gas molecules and organic compounds, resulting from the direct injection of hot carriers into the lowest unoccupied molecular orbital of the adsorbate molecule. The excellent light trapping property and high efficiency of hot charge-carrier generation through electromagnetic surface plasmon decay have been identified as the dominant mechanisms that promote energy-intensive chemical reactions at room temperature and atmospheric pressure. However, understanding the electromagnetic effects of plasmonics and distinguishing them from chemical effects in photocatalysis is challenging. While there exist several reviews underlining the experimental observations of plasmonic effects, this critical review addresses the physical origin of the various plasmon-related phenomena and how they can promote photocatalysis. The conditions under which each plasmonic effect dominates and how to distinguish one from another is also discussed. Finally, future research directions are proposed with the aim to accelerate progress in this field at the interface between chemistry and physics

Tungsten Oxide-Based Z-Scheme for Visible Light-Driven Hydrogen Production from Water Splitting

The stoichiometric water splitting using a solar-driven Z-scheme approach is an emerging field of interest to address the increasing renewable energy demand and environmental concerns. So far, the reported Z-scheme must comprise two populations of photocatalysts. In the present work, only tungsten oxides are used to construct a robust Z-scheme system for complete visible-driven water splitting in both neutral and alkaline solutions, where sodium tungsten oxide bronze (Na0.56WO3–x) is used as a H2 evolution photocatalyst and two-dimensional (2D) tungsten trioxide (WO3) nanosheets as an O2 evolution photocatalyst. This system efficiently produces H2 (14 μmol h–1) and O2 (6.9 μmol h–1) at an ideal molar ratio of 2:1 in an aqueous solution driven by light, resulting in a remarkably high apparent quantum yield of 6.06% at 420 nm under neutral conditions. This exceptional selective H2 and O2 production is due to the preferential adsorption of iodide (I–) on Na0.56WO3–x and iodate (IO3–) on WO3, which is evidenced by both experiments and density functional theory calculation. The present liquid Z-scheme in the presence of efficient shuttle molecules promises a separated H2 and O2 evolution by applying a dual-bed particle suspension system, thus a safe photochemical process

Polymer Photoelectrodes for Solar Fuel Production: Progress and Challenges

Converting solar energy to fuels has attracted substantial interest over the past decades because it has the potential to sustainably meet the increasing global energy demand. However, achieving this potential requires significant technological advances. Polymer photoelectrodes are composed of earth-abundant elements, e.g. carbon, nitrogen, oxygen, hydrogen, which promise to be more economically sustainable than their inorganic counterparts. Furthermore, the electronic structure of polymer photoelectrodes can be more easily tuned to fit the solar spectrum than inorganic counterparts, promising a feasible practical application. As a fast-moving area, in particular, over the past ten years, we have witnessed an explosion of reports on polymer materials, including photoelectrodes, cocatalysts, device architectures, and fundamental understanding experimentally and theoretically, all of which have been detailed in this review. Furthermore, the prospects of this field are discussed to highlight the future development of polymer photoelectrodes

Tungsten oxide-based Z-scheme for visible light-driven hydrogen production from water splitting

The stoichiometric water splitting using a solar-driven Z-scheme approach is an emerging field of interest to address the increasing renewable energy demand and environmental concerns. So far, the reported Z-scheme must comprise two populations of photocatalysts. In the present work, only tungsten oxides are used to construct a robust Z-scheme system for complete visible-driven water splitting in both neutral and alkaline solutions, where sodium tungsten oxide bronze (Na0.56WO3–x) is used as a H2 evolution photocatalyst and two-dimensional (2D) tungsten trioxide (WO3) nanosheets as an O2 evolution photocatalyst. This system efficiently produces H2 (14 μmol h–1) and O2 (6.9 μmol h–1) at an ideal molar ratio of 2:1 in an aqueous solution driven by light, resulting in a remarkably high apparent quantum yield of 6.06% at 420 nm under neutral conditions. This exceptional selective H2 and O2 production is due to the preferential adsorption of iodide (I–) on Na0.56WO3–x and iodate (IO3–) on WO3, which is evidenced by both experiments and density functional theory calculation. The present liquid Z-scheme in the presence of efficient shuttle molecules promises a separated H2 and O2 evolution by applying a dual-bed particle suspension system, thus a safe photochemical process

From scrap metal to highly efficient electrodes: harnessing the nanotextured surface of swarf for effective utilisation of Pt and Co for hydrogen production

Hydrogen is considered to be the key element to achieving climate neutrality, leading to a massive demand for electrocatalysts. This work explores the transformation of metal waste into active and stable electrode materials for water splitting by modifying the surface through atomic deposition of platinum (Pt) and cobalt (Co). Our study finds that with the addition of only 28 μg cm−2 of Pt and 30 μg cm−2 of Co to metal waste, high-performance electrolysis can be achieved. We investigated discarded stainless-steel (SST), titanium (Ti), and nickel (Ni) alloys and found that they had nanotextured surfaces, consisting of 10–50 nm wide grooves, which offered an excellent platform for effective bonding of Pt or Co atoms. We demonstrate a strong synergistic relationship between the metal of the swarf surface and the metal of catalytically active centers, such that only some combinations lead to effective electrocatalysts. Furthermore, we discovered that the surface density of atomically deposited Pt or Co has a profound impact on the nanoscale morphology of the active centers, providing a mechanism for the optimization of electrocatalytic characteristics. For instance, the optimal Pt loading (28 μg cm−2) on Ti swarf yields 5–20 nm Pt nanoparticles within the grooves with exceptional hydrogen evolution reaction (HER) activity. Similarly, the optimal surface density of Co (30 μg cm−2) on Ni swarf generates ∼100 nm interlinked flakes of Co(OH)2 with outstanding oxygen evolution reaction (OER) performance. Combining these best electrodes in a full-cell electrolyser resulted in a current density of 40 mA cm−2 at 1.6 V vs. RHE and the rates of H2 and O2 production of 22.09 and 10.75 mmol min−1, respectively, with 100% faradaic efficiency with no decrease in activity in 24 hours. This study opens the door to more sustainable electrode fabrication and effective hydrogen production in alkaline water electrolysis

Direct Deposition of Copper Atoms onto Graphitic Step Edges Lowers Overpotential and Improves Selectivity of Electrocatalytic CO2 Reduction

Minimizing our reliance on bulk precious metals is to increase the fraction of surface atoms and improve the metal-support interface. In this work, we employ a solvent/ligand/counterion-free method to deposit copper in the atomic form directly onto a nanotextured surface of graphitized carbon nanofibers (GNFs). Our results demonstrate that under these conditions, copper atoms coalesce into nanoparticles securely anchored to the graphitic step edges, limiting their growth to 2–5 nm. The resultant hybrid Cu/GNF material displays remarkable electrocatalytic properties in CO2 reduction reaction (CO2RR), exhibiting selectivity for formate production with a faradaic efficiency of ~ 94% at a low overpotential of 0.17 V and an exceptionally high turnover frequency of 2.78×106 h− 1. The Cu nanoparticles adhered to the graphitic step edges significantly enhance electron transfer to CO2, with the formation of CO2∙− intermediate identifiedas the rate-determining step. Long-term CO2RR tests coupled with atomic-scale elucidation of changes in Cu/GNF reveal nanoparticles coarsening, and a simultaneous increase in the fraction of single Cu atoms. These changes disfavour CO2RR, as confirmed by density functional theory calculations, revealing that CO2 cannot effectively compete with H2O for adsorption on single Cu atoms on the graphitic surfaces

Author Correction: Single-atom Cu anchored catalysts for photocatalytic renewable H2 production with a quantum efficiency of 56%

Correction to: Nature Communications https://doi.org/10.1038/s41467-021-27698-3, published online 10 January 2022.In Supplementary Fig. 28b in the Supplementary PDF for this article, the figure panel incorrectly read ‘345 mW/cm2’ but should have been ‘34.5 mW/cm2’.In the caption of Supplementary Fig. 20 in the Supplementary PDF for this article, the term ‘isotropic analysis’ should have read ‘isotopic analysis’.In the caption of Supplementary Fig. 21 in the Supplementary PDF for this article, the term ‘isotropic analysis’ should have read ‘isotopic analysis’.In the caption of Supplementary Fig. 28b in the Supplementary PDF for this article, the term ‘isotropic test’ should have read ‘isotopic test’

Synergy of nanocrystalline carbon nitride with Cu single atom catalyst leads to selective photocatalytic reduction of CO2 to methanol

Carbon nitride (C3N4) possesses both a band gap in the visible range and a low-lying conduction band potential, suitable for water splitting and CO2 reduction reactions (CO2RR). Yet, bulk C3N4 (b-C3N4) suffers from structural disorder leading to sluggish reaction kinetics. This can be improved by graphitisation; however, current processes in the literature, lead to a variety of graphitised C3N4 (g-C3N4), making it difficult to link the degrees of graphitisation with the functional properties. Herein, we employ complementary analyses, including electrochemical impedance, photoluminescence, and photocurrent, to elucidate structure–property–function relationships. Guided by the descriptors, we developed a facile two-step annealing method that yields nanocrystalline carbon nitride (nc-C3N4), comprising nanoscale graphitic domains within an amorphous matrix. The nanocrystalline grains of nc-C3N4 allow effective immobilisation of Cu atoms and stabilisation of low oxidation states (Cu(I)). Electron microscopy and energy-dispersive X-ray spectroscopy demonstrate that Cu is atomically dispersed. Importantly, the addition of only 0.11 wt% of copper to nc-C3N4 drastically decreases the charge recombination and resistance to change transfer. The synergy of the Cu single-atom catalyst and nanocrystalline domains in carbon nitride (Cu/nc-C3N4) leads to a remarkable 99% selectivity towards methanol production with a rate of 316 μmol gcat−1 h−1 during the photocatalytic CO2RR, which is absent in Cu/b-C3N4