Anchoring Cs+ Ions on Carbon Vacancies for Selective CO2 Electroreduction to CO at High Current Densities in Membrane Electrode Assembly Electrolyzers.

Electrolyte cations have been demonstrated to effectively enhance the rate and selectivity of the electrochemical CO2 reduction reaction (CO2RR), yet their implementation in electrolyte-free membrane electrode assembly (MEA) electrolyzer presents significant challenges. Herein, an anchored cation strategy that immobilizes Cs+ on carbon vacancies was designed and innovatively implemented in MEA electrolyzer, enabling highly efficient CO2 electroreduction over commercial silver catalyst. Our approach achieves a CO partial current density of approximately 500 mA cm-2 in the MEA electrolyzer, three-fold enhancement compared to pure Ag. In-situ Raman and theoretical analyses, combined with machine learning potentials, reveal anchored Cs induces an electric field that significantly promotes the adsorption of *CO2- intermediates through performing muti-point energy calculations on each structure. Furthermore, reduced adsorption of *OH intermediates effectively hampers competing hydrogen evolution reaction, as clarified by disk electrode experiments and density functional theory studies. Additionally, coupling our system with commercial polysilicon solar cells yields a notable solar-to-CO energy conversion efficiency of 8.3%. This study opens a new avenue for developing effective cation-promoting strategy in MEA reactors for efficient CO2RR.

Promoting water dissociation for efficient solar driven CO2 electroreduction via improving hydroxyl adsorption.

Exploring efficient electrocatalysts with fundamental understanding of the reaction mechanism is imperative in CO2 electroreduction. However, the impact of sluggish water dissociation as proton source and the surface species in reaction are still unclear. Herein, we report a strategy of promoting protonation in CO2 electroreduction by implementing oxygen vacancy engineering on Bi2O2CO3 over which high Faradaic efficiency of formate (above 90%) and large partial current density (162 mA cm-2) are achieved. Systematic study reveals that the production rate of formate is mainly hampered by water dissociation, while the introduction of oxygen vacancy accelerates water dissociation kinetics by strengthening hydroxyl adsorption and reduces the energetic span of CO2 electroreduction. Moreover, CO3* involved in formate formation as the key surface species is clearly identified by electron spin resonance measurements and designed in situ Raman spectroscopy study combined with isotopic labelling. Coupled with photovoltaic device, the solar to formate energy conversion efficiency reaches as high as 13.3%.

Precisely Tailoring Nitrogen Defects in Carbon Nitride for Efficient Photocatalytic Overall Water Splitting.

Precisely tailoring the nitrogen defects has been verified to be a promising approach for promoting the photocatalytic efficiency of C3N4. Herein, two-coordinated-N vacancies are selectively introduced into the C3N4 framework by a facile Cl- modification method, whereas its concentration can be facilely tuned by varying Cl- usage in the process of thermal polymerization. Impressively, the optimal defective C3N4 (20 mg) exhibited superior hydrogen and oxygen evolution rates of 48.2 and 21.8 µmol h-1, respectively, in photocatalytic overall water splitting and an apparent quantum efficiency of 6.9% at 420 nm, the highest of reported single-component C3N4 photocatalysts for overall water splitting. Systematic studies including XPS, DFT simulations, and NEXAFS reveal that Cl- modification preferentially facilitates the introduction of two-coordinated-N vacancies through tuning the formation energy and promotes charge carrier separation efficiency, thereby greatly enhancing the photocatalytic efficiency. This work allows for a viable approach to rationally designing defective C3N4 for efficient photocatalysis.

Hydrated electrons mediated in-situ construction of cubic phase CdS/Cd thin layer on a millimeter-scale support for photocatalytic hydrogen evolution.

In this study, non-noble metal Cd decorated cubic phase CdS (CdS/Cd) thin layer on a millimeter-scale chitosan-Mg(OH)2 xerogel beads (CMB) were elaborately designed and successfully synthesized via facile hydrated electrons (eaq•-) assistant strategy. The in-situ formation of metallic Cd was driven by eaq•- generated from UV/Na2SO3 process. Owing to metallic Cd, CMB@CdS/Cd exhibited better visible-light absorption ability and more efficient separation capability for photo-induced carriers, its hydrogen production efficiency was about threefold improved compared to CMB@CdS. Both characterization methods and density functional theory calculations determined a built-in electric field from metallic Cd to CdS and Ohmic-contact between Cd and CdS, which largely promoted the carriers transfer efficiency. Moreover, the introduction of metallic Cd on the CdS could reduce the ΔGH*, thus greatly boosting the photocatalytic hydrogen production efficiency. This work provides a simple and green approach to construct metallic Cd coupled semiconductor to achieve efficient photocatalytic applications.

Zr-Al co-doped SrTiO3 with suppressed charge recombination for efficient photocatalytic overall water splitting.

Zr-Al co-doped SrTiO3 with reduced Ti3+ concentration demonstrates more than 2 times enhancement compared with Al-doped SrTiO3 in photocatalytic overall water splitting. Systematic studies reveal that the co-doping of Zr4+ can reduce the substitution of Ti4+ by Al3+ and effectively suppress the formation of charge carrier recombination centers (Ti3+).

Insights into the Operation of Noble-Metal-Free Cocatalyst 1T-WS2 -Decorated Zn0.5 Cd0.5 S for Enhanced Photocatalytic Hydrogen Evolution.

Due to inefficient charge separation and low surface catalytic conversion efficiencies, cocatalysts are required for achieving photocatalytic hydrogen evolution. Being a noble-metal-free cocatalyst, metallic 1T-WS2 with excellent conductivity can function for this reaction. Herein, 1T-WS2 /Zn0.5 Cd0.5 S is constructed via a simple and feasible grinding approach. The composite containing 7.5 % 1T-WS2 in 1T-WS2 /Zn0.5 Cd0.5 S achieves a hydrogen evolution rate of 61.65 mmol g-1 h-1 and an external quantum efficiency of 8.04 % at 420 nm, which is 37 times that of bare Zn0.5 Cd0.5 S (1.67 mmol g-1 h-1 ). The electrical conductivity of metallic 1T-WS2 reduces the transfer impedance at the interface and thus accelerates the non-radiative energy transfer and electron transport rate. The different Fermi levels of 1T-WS2 and Zn0.5 Cd0.5 S form a Schottky junction, which promotes the transfer of photogenerated electrons from Zn0.5 Cd0.5 S to 1T-WS2 . More importantly, the close interface contact between 1T-WS2 and Zn0.5 Cd0.5 S results in strong electron interactions, which is conducive to the spatial separation of photogenerated electrons and holes. This work will further expand the application of 1T-WS2 in the photocatalytic hydrogen evolution process.

Boron Dopant Induced Electron-Rich Bismuth for Electrochemical CO2 Reduction with High Solar Energy Conversion Efficiency.

Electrochemical CO2 reduction to formate offers a mild and feasible pathway for the utilization of CO2 , and bismuth is a promising metal for its unique hydrogen evolution reaction inhibition. Reported works of Bi-based electrodes generally exhibit high selectivity while suffering from relatively narrow working potential range. From the perspective of electronic modification engineering, B-doped Bi is prepared by a facile chemical reduction method in this work. With B dopant, above 90% Faradaic efficiency for formate over a broad window of working potential of -0.6 to -1.2 V (vs. reversible hydrogen electrode) is achieved. In situ Raman spectroscopy, X-ray adsorption spectroscopy, and computational analysis demonstrate that the B dopant induces the formation of electron-rich bismuth, which is in favor of the formation of formate by fine-tuning the adsorption energy of *OCHO. Moreover, full-cell electrolysis system coupled with photovoltaic device is constructed and achieves the solar-to-formate conversion efficiency as high as 11.8%.

Designing Carbonized Loofah Sponge Architectures with Plasmonic Cu Nanoparticles Encapsulated in Graphitic Layers for Highly Efficient Solar Vapor Generation.

Solar vapor generation represents a promising approach to alleviate water shortage for producing fresh water from undrinkable water resources. Although Cu-based plasmonics have attracted tremendous interest due to efficient light-to-heat conversion, their application faces great challenges in the oxidation resistance of Cu and low evaporation rate. Herein, a hybrid of three-dimensional carbonized loofah sponges and graphene layers encapsulated Cu nanoparticles is successfully synthesized via a facile pyrolysis method. In addition to effective light harvesting, the localized heating effect of stabilized Cu nanoparticles remarkably elevated the surface temperature of Cu@C/CLS to 72 °C, and a vapor generation rate as high as 1.54 kg m-2 h-1 with solar thermal efficiency reaching 90.2% under 1 Sun illumination was achieved. A study in the purification of sewage and muddy water with Cu@C/CLS demonstrates a promising perspective in a practical application. These results may offer a new inspiration for the design of efficient nonprecious Cu-based photothermal materials.

Efficient photocatalytic conversion of CH4 into ethanol with O2 over nitrogen vacancy-rich carbon nitride at room temperature.

A record ethanol production rate of 281.6 µmol g-1 h-1 for the photocatalytic conversion of methane over nitrogen vacancy-rich carbon nitride at room temperature was achieved. Systematic studies demonstrate that the CH4 was activated by the highly reactive ˙OH radicals generated, via H2O2, from the photo-reduction of O2 with H2O.

Cl- modification for effective promotion of photoelectrochemical water oxidation over BiVO4.

Postsynthetic treatment is an attractive method to enhance photoelectrochemical water splitting. The facile Cl- modification approach developed in this work remarkably promotes the photocurrent density of BiVO4 up to 2.7 mA cm-2 by facilitating carrier transfer in addition to a charge carrier separation efficiency enhancement.

Copper nanoparticles selectively encapsulated in an ultrathin carbon cage loaded on SrTiO3 as stable photocatalysts for visible-light H2 evolution via water splitting.

One-nanometre-thick carbon cage encapsulated copper nanopaticles on SrTiO3 (STO) synthesized through a facile chemical vapour deposition method showed remarkable stability and performance for both photocatalytic hydrogen evolution and thermocatalytic reduction of 4-nitrophenol. X-ray photoelectron spectroscopy and Raman results demonstrate that the graphene cage effectively protected Cu nanoparticles from being oxidized.

Remarkable Visible-Light Photocatalytic Activity Enhancement over Au/p-type TiO2 Promoted by Efficient Interfacial Charge Transfer.

Metal-induced photocatalysis has emerged as a promising approach for exploiting visible-light-responsive composite materials for solar energy conversion, which is generally hindered by low photocatalytic efficiency. Herein, for the first time, an Au/p-TiO2 (p-type TiO2) strategy with the hole transfer mechanism is developed, remarkably promoting visible-light photocatalytic performance. An efficient acetone evolution rate (138 µmol·g-1·h-1) in the photocatalytic isopropyl alcohol (IPA) degradation under λex = 500 nm light (light intensity, 5.5 mW/cm2) was achieved over Au/p-TiO2, which is approximately 5 times as high as that over Au/n-TiO2 under the same conditions. Photoluminescence and electrochemical impedance spectroscopy measurements indicate enhanced charge carrier separation and transfer for Au/p-TiO2. In an elaborate study, apparent quantum efficiency and transmission electron microscopy characterization on selective PbO2 deposition over p-TiO2 revealed that visible-light-excited holes other than electrons generated in the Au interband transition transferred to p-TiO2, which is opposite to the general route in Au/n-TiO2 (n-type TiO2). Energetic holes generated in the d band of Au led to a fluent transfer across the Schottky barrier, which is further confirmed by the IPA photodegradation mechanism study with different scavengers over Au/p-TiO2. This discovery opens up new opportunities in designing and developing efficient metal semiconductor composite materials with visible-light response.

0D/2D Heterojunctions of Vanadate Quantum Dots/Graphitic Carbon Nitride Nanosheets for Enhanced Visible-Light-Driven Photocatalysis.

0D/2D heterojunctions, especially quantum dots (QDs)/nanosheets (NSs) have attracted significant attention for use of photoexcited electrons/holes due to their high charge mobility. Herein, unprecedent heterojunctions of vanadate (AgVO3 , BiVO4 , InVO4 and CuV2 O6 ) QDs/graphitic carbon nitride (g-C3 N4 ) NSs exhibiting multiple unique advances beyond traditional 0D/2D composites have been developed. The photoactive contribution, up-conversion absorption, and nitrogen coordinating sites of g-C3 N4 NSs, highly dispersed vanadate nanocrystals, as well as the strong coupling and band alignment between them lead to superior visible-light-driven photoelectrochemical (PEC) and photocatalytic performance, competing with the best reported photocatalysts. This work is expected to provide a new concept to construct multifunctional 0D/2D nanocomposites for a large variety of opto-electronic applications, not limited in photocatalysis.

CO tolerance of Pt/FeOx catalyst in both thermal catalytic H2 oxidation and electrochemical CO oxidation: the effect of Pt deficit electron state.

CO poisoning of Pt catalysts is one of the major challenges to the commercialization of proton exchange membrane fuel cells. One promising solution is to develop CO-tolerant Pt-based catalysts. A facilely synthesized Pt/FeOx catalyst exhibited outstanding CO tolerance in the oxidation of H2 and electrochemical CO stripping. Light-off temperature of H2O formation over Pt/FeOx was achieved even below 30 °C in the presence of 3000 ppm CO at a space velocity of 18 000 mL g-1cat h-1. For the electrochemical oxidation of CO, the onset and peak potentials decreased by 0.17 V and 0.10 V, respectively, in comparison with those of commercial Pt/C. More importantly, by a combination of hard X-ray photoemission spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies it was found that the decreased electron density of Pt in Pt/FeOx enhanced the mobility of adsorbed CO, suppressed Pt-CO bonding and significantly increased the CO tolerance of Pt/FeOx.

Nanometals for Solar-to-Chemical Energy Conversion: From Semiconductor-Based Photocatalysis to Plasmon-Mediated Photocatalysis and Photo-Thermocatalysis.

Nanometal materials play very important roles in solar-to-chemical energy conversion due to their unique catalytic and optical characteristics. They have found wide applications from semiconductor photocatalysis to rapidly growing surface plasmon-mediated heterogeneous catalysis. The recent research achievements of nanometals are reviewed here, with regard to applications in semiconductor photocatalysis, plasmonic photocatalysis, and plasmonic photo-thermocatalysis. As the first important topic discussed here, the latest progress in the design of nanometal cocatalysts and their applications in semiconductor photocatalysis are introduced. Then, plasmonic photocatalysis and plasmonic photo-thermocatalysis are discussed. A better understanding of electron-driven and temperature-driven catalytic behaviors over plasmonic nanometals is helpful to bridge the present gap between the communities of photocatalysis and conventional catalysis controlled by temperature. The objective here is to provide instructive information on how to take the advantages of the unique functions of nanometals in different types of catalytic processes to improve the efficiency of solar-energy utilization for more practical artificial photosynthesis.

High performance Au-Cu alloy for enhanced visible-light water splitting driven by coinage metals.

A Au-Cu alloy strategy is, for the first time, demonstrated to be effective in enhancing visible-light photocatalytic H2 evolution via promoting metal interband transitions. Au3Cu/SrTiO3, in which oxidation of Cu was successfully restrained, showed the highest visible-light H2 evolution activity.

Highly efficient and stable photocatalytic reduction of CO2 to CH4 over Ru loaded NaTaO3.

An efficient and stable photocatalytic activity was obtained over NaTaO3 by introducing an electron donor (H2) into the CO2 reduction process with water. Ru/NaTaO3 demonstrated the best activity (CH4 51.8 µmol h(-1) g(-1)) and product selectivity in converting CO2 to CH4.

A highly durable p-LaFeO3/n-Fe2O3 photocell for effective water splitting under visible light.

A new p-type photocathode LaFeO3 was successfully fabricated, and a stable (120 h) and effective water splitting (H2: 11.5 µmol h(-1), O2: 5.7 µmol h(-1)) was realized via construction of a p-LaFeO3/n-Fe2O3 photocell. This study offers a new alternative to p-type photocathode materials and the low cost design of durable PEC devices for solar conversion.

Constructing a multicomponent junction for improved visible-light photocatalytic performance induced by Au nanoparticles.

Au induced visible-light photocatalytic performance is, for the first time, demonstrated to be effectively enhanced by a proper construction of a junction nanostructure. A study of the ˙O2(-) and H2O2 radicals indicates the efficient electron transfer across the Au-SrTiO3-TiO2 composite facilitated by the junction effect is responsible for the enhancement, and ultimately promotes the photocatalytic process.

Photocatalytic reduction of carbon dioxide by hydrous hydrazine over Au-Cu alloy nanoparticles supported on SrTiO3/TiO2 coaxial nanotube arrays.

Efficient photocatalytic conversion of CO2 into CO and hydrocarbons by hydrous hydrazine (N2H4⋅H2O) is achieved on SrTiO3/TiO2 coaxial nanotube arrays loaded with Au-Cu bimetallic alloy nanoparticles. The synergetic catalytic effect by the Au-Cu alloy nanoparticles and the fast electron-transfer in SrTiO3/TiO2 coaxial nanoarchitecture are the main reasons for the efficiency, while N2H4⋅H2O as the H source and electron donor provides a reducing atmosphere to protect the surface Cu atoms from oxidation, therefore maintaining the alloying effect which is the basis for the high photocatalytic activity and stability. This approach opens a feasible route to enhance the photocatalytic efficiency, which also benefits the development of photocatalysts and co-catalysts.