Modulating the Oxidation State of Titanium via Dual Anions Substitution for Efficient N2 Electroreduction

Interfacial Push-Pull Dynamics Enable Rapid Had Desorption for Enhanced Formate Electrooxidation

The electrocatalytic conversion of formate in alkaline solutions is of paramount significance in the realm of fuel cell applications. Nonetheless, the adsorptive affinity of adsorbed hydrogen (Had) on the catalyst surface has traditionally impeded the catalytic efficiency of formate in such alkaline environments. To circumvent this challenge, our approach introduces an interfacial push-pull effect on the catalyst surface. This mechanism involves two primary actions: First, the anchoring of palladium (Pd) nanoparticles on a phosphorus-doped TiO2 substrate (Pd/TiO2-P) promotes the formation of electron-rich Pd with a downshifted d band center, thereby "pushing" the desorption of Had from the Pd active sites. Second, the TiO2-P support diminishes the energy barrier for Had transfer from the Pd sites to the support itself, "pulling" Had to effectively relocate from the Pd active sites to the support. The resultant Pd/TiO2-P catalyst showcases a remarkable mass activity of 4.38 A mgPd-1 and outperforms the Pd/TiO2 catalyst (2.39 A mgPd-1) by a factor of 1.83. This advancement not only surmounts a critical barrier in catalysis but also delineates a scalable pathway to bolster the efficacy of Pd-based catalysts in alkaline media.

Understanding Bridging Sites and Accelerating Quantum Efficiency for Photocatalytic CO2 Reduction

We report a novel double-shelled nanoboxes photocatalyst architecture with tailored interfaces that accelerate quantum efficiency for photocatalytic CO2 reduction reaction (CO2RR) via Mo-S bridging bonds sites in Sv-In2S3@2H-MoTe2. The X-ray absorption near-edge structure shows that the formation of Sv-In2S3@2H-MoTe2 adjusts the coordination environment via interface engineering and forms Mo-S polarized sites at the interface. The interfacial dynamics and catalytic behavior are clearly revealed by ultrafast femtosecond transient absorption, time-resolved, and in situ diffuse reflectance-Infrared Fourier transform spectroscopy. A tunable electronic structure through steric interaction of Mo-S bridging bonds induces a 1.7-fold enhancement in Sv-In2S3@2H-MoTe2(5) photogenerated carrier concentration relative to pristine Sv-In2S3. Benefiting from lower carrier transport activation energy, an internal quantum efficiency of 94.01% at 380 nm was used for photocatalytic CO2RR. This study proposes a new strategy to design photocatalyst through bridging sites to adjust the selectivity of photocatalytic CO2RR.

Powerful Orbital Hybridization of Copper-Silver Bimetallic Nanosheets for Electrocatalytic Nitrogen Reduction to Ammonia

Electrochemical nitrogen reduction (eNRR) is a promising strategy to replace the energy- and capital-intensive Haber-Bosch process. Unfortunately, the low selectivity of the eNRR process impedes the industrial application of this approach. In this work, a highly efficient and stable NRR electrocatalyst is obtained via coreduction of Cu and Ag precursors using the holly leaves as reducing agents. The as-obtained Cu₃Ag bimetallic nanosheets exhibit excellent NRR performance with an NH₃ production rate of 31.3 μg h^-1 mg^-1_cat. and a Faradaic efficiency of 31.3% at -0.2 V vs RHE. According to density functional theory (DFT) calculation, the outstanding performance of Cu₃Ag bimetallic nanosheets could be caused by the fact that Ag optimizes the 3d orbital occupation of Cu and synergistically enhances the charge transfer during the NRR process, resulting in a suitable adsorption strength of the intermediates.

Defective TiO2- x for High-Performance Electrocatalytic NO Reduction toward Ambient NH3 Production

Synthesis of green ammonia (NH₃ ) via electrolysis of nitric oxide (NO) is extraordinarily sustainable, but multielectron/proton-involved hydrogenation steps as well as low concentrations of NO can lead to poor activities and selectivities of electrocatalysts. Herein, it is reported that oxygen-defective TiO₂ nanoarray supported on Ti plate (TiO_{2- x} /TP) behaves as an efficient catalyst for NO reduction to NH₃ . In 0.2 m phosphate-buffered electrolyte, such TiO_{2- x} /TP shows competitive electrocatalytic NH₃ synthesis activity with a maximum NH₃ yield of 1233.2 µg h^-1  cm^-2 and Faradaic efficiency of 92.5%. Density functional theory calculations further thermodynamically faster NO deoxygenation and protonation processes on TiO_{2- x} (101) compared to perfect TiO₂ (101). And the low energy barrier of 0.7 eV on TiO_{2- x} (101) for the potential-determining step further highlights the greatly improved intrinsic activity. In addition, a Zn-NO battery is fabricated with TiO_{2- x} /TP and Zn plate to obtain an NH₃ yield of 241.7 µg h^-1  cm^-2 while providing a peak power density of 0.84 mW cm^-2 .

Oxide-Derived Bismuth as an Efficient Catalyst for Electrochemical Reduction of Flue Gas

Post-combustion flue gas (mainly containing 5-40% CO₂ balanced by N₂ ) accounts for about 60% global CO₂ emission. Rational conversion of flue gas into value-added chemicals is still a formidable challenge. Herein, this work reports a β-Bi₂ O₃ -derived bismuth (OD-Bi) catalyst with surface coordinated oxygen for efficient electroreduction of pure CO₂ , N_2, and flue gas. During pure CO₂ electroreduction, the maximum Faradaic efficiency (FE) of formate reaches 98.0% and stays above 90% in a broad potential of 600 mV with a long-term stability of 50 h. Additionally, OD-Bi achieves an ammonia (NH₃ ) FE of 18.53% and yield rate of 11.5 µg h^-1 mg_cat ^-1 in pure N₂ atmosphere. Noticeably, in simulated flue gas (15% CO₂ balanced by N₂ with trace impurities), a maximum formate FE of 97.3% is delivered within a flow cell, meanwhile above 90% formate FEs are obtained in a wide potential range of 700 mV. In-situ Raman combined with theory calculations reveals that the surface coordinated oxygen species in OD-Bi can drastically activate CO₂ and N₂ molecules by selectively favors the adsorption of *OCHO and *NNH intermediates, respectively. This work provides a surface oxygen modulation strategy to develop efficient bismuth-based electrocatalysts for directly reducing commercially relevant flue gas into valuable chemicals.

·H effectively enhance electrocatalytic nitrogen fixation

Nowadays, most reported ammonia (NH₃) yields and Faradaic efficiency (FE) of electrocatalysts are very low in the field of electrocatalytic nitrogen reduction reactions (NRR). Here, we are reported ·H for the first time in the field of electrocatalytic NRR, which are generated by sulfite (SO₃^2-) and H₂O in electrolyte solutions upon exposure to UV light. The high NH₃ yields can achieve 100.7 μg h^-1 mg_cat^-1, while stability can achieve 64 h and the FE can achieve 27.1% at -0.3 V (vs. RHE) with UV irradiation. In situ Fourier transform infrared spectroscopy (FTIR), electron spin resonance (ESR), density functional theory (DFT) and ¹H nuclear magnetic resonance (NMR) tests showed that the ∙H effectively lowered the reaction energy barrier at each step of the NRR process and inhibits the occurrence of competitive hydrogen evolution reaction (HER). This explores the path and provides ideas for the field of electrocatalysis involving water.

First-principles screening of transition metal doped anatase TiO2(101) surfaces for the electrocatalytic nitrogen reduction

The electrocatalytic nitrogen reduction reaction (eNRR) has been attracting intensive scientific attention as a potential alternative to the industrial Haber-Bosch process for ammonia production. Although many materials have been investigated, optimal catalysts for the reaction remain to be found. In this work, we performed the theoretical screening of 3d-5d transition metal doped anatase TiO₂ for the eNRR. The most favorable doping site of each transition metal on the (101) surface was located. We found that the doping of transition metals promotes the formation of oxygen vacancies which are beneficial for the reaction. The scaling relations between the energies of the key intermediates were investigated. Using a machine learning algorithm (SVM), we identified two adsorption modes for the end-on adsorbed *HNN, which exhibited different scaling relations with *NH₂. From a two-step process, we screened out several candidates, among which Au and Ta were proposed to be the most efficient dopants. Electronic structure analysis reveals that they can efficiently lower the energy of the intermediates. These results should be helpful for the design of more efficient TiO₂-based catalysts for the eNRR.

Unifying the Nitrogen Reduction Activity of Anatase and Rutile TiO2 Surfaces

TiO₂ is a model transition metal oxide that has been applied frequently in both photocatalytic and electrocatalytic nitrogen reduction reactions (NRR). However, the phase which is more NRR active still remains a puzzle. This work presents a theoretical study on the NRR activity of the (001), (100), (101), and (110) surfaces of both anatase and rutile TiO₂ . We found that perfect surfaces are not active for NRR, while the oxygen vacancy can promote the reaction by providing excess electrons and low-coordinated Ti atoms that enhance the binding of the key intermediate (HNN*). The NRR activity of the eight facets can be unified into a single scaling line. The anatase TiO₂ (101) and rutile TiO₂ (101) surfaces were found to be the most and the second most active surfaces with a limiting potential of -0.91 V and -0.95 V respectively, suggesting that the TiO₂ NRR activity is not very phase-sensitive. For photocatalytic NRR, the results suggest that the anatase TiO₂ (101) surface is still the most active facet. We further found that the binding strength of key intermediates scale well with the formation energy of oxygen vacancy, which is determined by the oxygen coordination number and the degree of relaxation of the surface after the creation of oxygen vacancy. This work provides a comprehensive understanding of the activity of TiO₂ surfaces. The results should be helpful for the design of more efficient TiO₂ -based NRR catalysts.