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Crystalline carbon nitride can potentially manifest heightened light-harvesting efficiency, coupled with proficient charge migration rates, attributable to the diminished count of recombination centers for photoexcited carriers. This phenomenon stems from the extensive π-conjugated framework and the dispersion of π-electrons. This investigation adopts a self-assembly strategy, utilizing hydrogen-bonded bridging melem with cyanuric acid, to yield crystalline oxygen-bridged carbon nitride. The strategic introduction of oxygen doping, positioned at the junction between heptazine units, and the crystalline architecture endow BCN with augmented photocatalytic H2 evolution capacity. This culminates in a H2 production rate under visible light irradiation that surpasses that of pristine BCN by approximately 23.2 times, and an apparent quantum efficiency (AQE) of 13.2% at 420 nm. The confluence of the oxygen-bridging mechanism and crystalline architecture within carbon nitride profoundly augments the partition and migration pace of photoexcited carriers, resulting in the amplified photocatalytic performance of BCN. This strategic paradigm charts a fresh trajectory toward an exponential augmentation of carbon nitride performance, nimbly regulating both crystalline architecture and elemental doping. [ABSTRACT FROM AUTHOR]

Developing a highly efficient and low-cost oxygen-evolution-reaction (OER) electrocatalyst is an important route to overcome the rate-determining step of water splitting. Here, we directly grew a CoS2 nanoarray core with an N-doped graphitic carbon (NGC) shell on Ni foam (NF) to construct a core–shell nanorod array electrode, CoS2@NGC@NF. The CoS2 core with a high work function (∼5.5 eV) tends to capture electrons from the NGC layer (4.5–5.2 eV) to induce an electron-poor NGC shell with a significant downshift of the carbon Fermi level, facilitating the adsorption of O-containing intermediates and affording decreased activation energy during the OER process. As a result, the three-dimensional NGC encapsulated CoS2 array assembly exhibited excellent electrocatalytic OER activity with a low overpotential of 243 mV at a current density of 10 mA cm−2 and a small Tafel slope of 71 mV dec−1 in 1.0 M KOH. Our findings may suggest that manipulating the interface energetics by the work function difference is a potential route to the design of high-performance OER electrocatalysts. [ABSTRACT FROM AUTHOR]

The substantial overpotential of CO2 activation, the complex CO2 reduction pathway, and the competitive H2 evolution reaction (HER) limit the practical applications of CO2-based electrochemical energy conversion and storage technologies due to their low energy efficiency and product selectivity. Here, we proposed a strategy that combines mesopores and redox-active couple to effectively capture CO2 and selectively generate CO product. As an example, we construct a redox-active couple, Zn2+/Zn+, on the low-crystallinity mesoporous ZnGa2O4 electrocatalyst. The mesopores not only help to capture CO2 effectively but also inhibit the H2 evolution. The weak lattice constraint of low crystallinity benefits the formation of a Zn2+/Zn+ redox couple to strongly interact with CO2 molecule for subsequent activation and catalytic conversion, thus effectively decreasing the activation energy of CO2 to the active species CO2− and accelerating the proton transfer to form the crucial COOH* intermediate. Consequently, this catalyst exhibited a high faradaic efficiency of 96% among Zn-based electrodes for CO generation at the relatively low applied potential of −1.4 V vs. Ag/AgCl (−0.8 V vs. RHE), and excellent stability during 10 h operation in a 0.1 M KHCO3 solution. [ABSTRACT FROM AUTHOR]

Understanding the mechanism underlying photocatalytic product selectivity will provide valuable guidance in developing novel catalysts and reaction pathways. In this article, the role of surface chemistry in product generation is well-demonstrated using LaTiO2N, Ta3N5, and their hybrids with dominant (002) and (020) facets, respectively. Photocatalytic test results show that CO2 could be reduced to CH4 and CO in the presence of LaTiO2N and Ta3N5 photocatalysts, respectively. The detected intermediates suggest that the reaction pathway could possibly be UGRAPHIC DISPLAY="INLINE" ID="UGT1" SRC="UGT1"/. Product selectivity is dependent on the ability to capture CO onto the photocatalyst surface, which is probably related to the electronegativity of the adsorption sites. Strong adsorption of CO on the LaTiO2N surface favors the subsequent hydrogenation reaction to generate CH4, while weak CO adsorption on Ta3N5 results in CO as the main product of CO2 reduction, which is demonstrated by theoretical calculations as well. Such product selectivity is mainly related to the surface chemistry of the photocatalyst and independent of the surface charge concentration. Our results provide a progressive understanding of selective product formation during photocatalytic CO2 reduction. [ABSTRACT FROM AUTHOR]

Oriented attachment (OA) has been widely used as a term to describe solution-based particle (generally, ＜10 nm in size) growth proceeding by crystallographic alignment. A big challenge in large-sized crystal growth by the OA crystallization process is the removal of the additives that cause the OA assembling process to occur. Here, we find that the molten salt environment is an ideal medium for OA growth of large-sized inorganic particles without the requirement of any additives. As an example, in Li ion-based molten salts, hundred-nanometer-size LaTaON2 single crystals with no specific morphology can spontaneously assemble into micrometer-size regular crystals. Theoretical and experimental evidence indicated that this OA growth process among the large-sized crystals is governed by a trade-off between electrostatic repulsion and van der Waals attraction, which can be adjusted by the adsorption difference of positive and negative ions on the crystal surface. Finally, due to the significant decrease in charge recombination at grain boundaries, the large single crystal electrode exhibited an enhanced photoelectrochemical performance of 5.1 mA cm−2 at 1.23VRHE, the highest performance among the previously reported LaTaON2 photoanodes. Our findings offer a new approach to assemble large-size single crystals for advanced nanodevices. [ABSTRACT FROM AUTHOR]

Charge separation/transfer and photocorrosion are two major factors limiting the photoelectrochemical (PEC) applications of the Ta3N5 photocatalyst. Herein, we have fabricated Ta3N5 single-crystal nanorods with Mg doping by flux-assisted crystal growth, aiming to shorten the charge transport distance and increase the electrical conductivity. The optimized Mg-doped Ta3N5 photoanodes exhibit an unprecedented PEC water splitting activity with an AM 1.5G photocurrent of 1.5 mA cm−2 at 1.23 VRHE. The high performance is attributed to the fact that the bulk modification, Mg doping, can induce oxygen-impurity surface states as effective electron trap centers, thus increasing the electrical conductivity of Ta3N5 and charge separation efficiency. After a conformal surface modification with CoOOH by a simple electrodeposition method as a water oxidation electrocatalyst to improve the hole extraction and reaction kinetics, the Mg-doped Ta3N5 photoanodes afford an over 4-fold increase in photocurrent (ca. 6.5 mA cm−2 at 1.23 VRHE) and about 70% retention of the initial photocurrent after 70 min irradiation at 1.0 VRHE. Our results testify that the bulk and surface co-modification is an effective route to develop high-performance PEC water splitting devices. [ABSTRACT FROM AUTHOR]

Inevitable surface defects on α-Fe2O3 photoanodes, a promising candidate for photoelectrochemical (PEC) water splitting with excellent stability and absorption in the visible light region, greatly limit their PEC performance for water oxidization. Surface modification is an effective strategy to decrease the negative effects of the surface defects. However, a challenge in understanding the nature of surface modification still remains. Here, we found that an ion-permeable Al2O3 coating layer can effectively prevent oxygen diffusion to the photoanode surface, thus suppressing the back reaction from oxygen reduction. The ion-permeable Al2O3 leads to ineffective surface state passivation due to the possible interface corrosion effect of OH− ions that decrease the interactions between Al2O3 and Fe2O3. In contrast, the ion-impermeable Al2O3 layer exhibits strong interactions with Fe2O3 and is mainly responsible for both surface state passivation and back reaction suppression, improving the photocurrent onset potential. Our results indicated that the modification of ion-impermeable passivation layers is a potential effective strategy to enhance the PEC performance. [ABSTRACT FROM AUTHOR]

The removal of nitrogen oxides (NOx) originating from human activities continues to be a challenge for environmental protection due to the lack of an efficient method to capture and convert nitrogen oxides. Here, as a typical example of a bifunctional catalyst, a new low-cost Ni–Ga based oxide catalyst with an inverse spinel structure was developed for NO removal. It exhibits the synergetic catalysis properties of Ni and Ga: strong NO capture properties from the Ni species and applicable NO catalytic conversion from both the Ni and Ga species. The NO removal by the Ni–Ga based catalyst is strongly dependent on the Ga ligand environment. The largely inverse spinel structure with an inversion parameter of 92% and the tetrahedral preference of Ga3+ greatly contribute to the high performance for NO conversion due to the electron transfer occurring easily in the low coordination environment of the Ga ions. The electron transfer process in the Ni–Ga based catalyst can be further activated by Zn doping, increasing the catalytic ability for NO conversion. Our results open up a new route for designing efficient catalysts, combining the strong gas capture properties of a specific element with high catalytic NO conversion properties, by constructing an appropriate element ligand environment. [ABSTRACT FROM AUTHOR]

Tailored nanostructures offer a new way to facilitate electron-hole separation and offer additional opportunities to generate unique photocatalysts that demonstrate novel light absorption, thermodynamic and kinetic properties. A simple and efficient approach to the synthesis of a large variety of g-C3N4 tailored nanostructures is reported. Herein, NH3 and H2O2 were used as controllable chemical scissors to tailor bulk g-C3N4 to a large variety of g-C3N4 nanostructures, which include exfoliated porous, quantum dot, nanomites and nanospindles. The tailored g-C3N4 shows a photoreactivity of H2 evolution 3.0 (pure water) and 4.1 (saturated KCl solution) times higher than bulk g-C3N4 under λ > 420 nm. We believe this strategy affords new opportunities for structural tuning of X-doped (X = N, S, P, and O) carbon materials, as well as their exploration in catalysis, organic synthesis, nanomedicine and energy storage. [ABSTRACT FROM AUTHOR]