5-Hydroxymethylfurfural oxidation reaction (HMFOR) is regarded as a promising approach to attain biomassderived high-value chemical products. As the HMFOR process is complicated, and the two-step oxidation of the aldehyde group and hydroxyl group in 5-hydroxymethylfurfural (HMF) is typically involved, it is fundamentally significant to understand the different catalytic processes for HMFOR. In this work, we identify direct and synergistic oxidation types for HMFOR on cobalt oxide catalysts. For the direct HMFOR process, Co 3 O 4 was found to have a higher activity for the aldehyde group than for the hydroxyl group due to the higher reaction barrier of hydration in the hydroxyl oxidation. By studying the hydroxyl oxidation behaviors in transition metal oxides, NiO exhibited optimal hydroxyl activity owing to the appropriate OH adsorption energy for alcohol dehydrogenation. Therefore, the optimal HMFOR performance was achieved by accurately introducing Ni into the tetrahedral catalytic sites of cobalt spinel oxides to improve the hydroxyl activity. The integrated catalytic sites enhanced the overall activity of HMFOR with 92.42% FDCA yield and 90.35% faradaic efficiency. This work provides a promising perspective for designing efficient electrocatalysts for HMFOR.

Searching for low-cost, environmentally friendly, and highly active catalysts for C−H bond activation in propane dehydrogenation (PDH) reaction remains a great challenge. Herein, SiO 2 nanomeshes (NMs) with ultrashort three-dimensional (3D) channels were constructed to effectively confine the Co single atoms (Co SAs/ SiO 2 NMs). The ultrashort 3D channels were formed by gasifying carbon in the self-assembled SiO 2 @polymer composites under the air atmosphere. The carbon removal process resulted in abundant oxygen (O*) defects in the channel windowsill that immobilized the dissociative Co 1 species to afford the sintering-resistant Co SAs/SiO 2 NMs catalyst. The as-obtained Co SAs/SiO 2 NMs with unsaturated Co−O 3 sites exhibited an outstanding PDH catalytic behavior (95% selectivity and 196 h −1 turnover frequency), superior to Co SAs/SiO 2 commerce (83%, 49 h −1 ), Co NPs/SiO 2 NMs (87%, 13 h −1 ), and most non-noble metal-based catalysts. Furthermore, Co SAs/SiO 2 NMs showed high long-term stability with no significant deactivation during 24 h of reaction. Theoretical and experimental analysis indicated that these unsaturated Co−O 3 sites could selectively activate the first and second C−H bonds and limit the further splitting of C−H (C) bonds during PDH. This work paves a way for designing high-efficiency single-atom catalysts for PDH.

While Fe–N–C materials exhibit great potential for catalyzing the oxygen reduction reaction (ORR), their activity origin, especially the significant activity difference in acidic and alkaline media, remains a long-standing conundrum hindering the development of such catalysts. Here, we show an unanticipated pH-dependent regulation mechanism in Fe–N–C materials via first-principles microkinetic computations that explicitly consider the pH, solvation, and electrode potential effects. We find that, under typical operating potentials, the well-established FeN4 centers of Fe −N–C catalysts, regardless of the pyridinic and pyrrolic-type N-coordination environments, are not adsorbate-free but covered by an intrinsic intermediate *OH at pH = 1 and *O at pH = 13, resulting in FeN4–OH and FeN4–O centers formed in situ. We evaluate the pH- and potential-dependent kinetics and thermodynamics of the real active Fe centers of Fe–N–C catalysts against experimental measurements. We demonstrate that the activity difference of Fe–N–C catalysts is attributed to the *O coordination-induced optimization of the electronic structure and intermediate adsorption over the *OH case. Our work provides the mechanistic insight into the pH effects and paves the way toward a more effective catalyst design.

With high theoretical capacity and operating voltage, KVPO 4 F is a potential high energy density cathode material for potassium-ion batteries. However, its performance is usually limited by F loss, poor electronic conductivity, and unsteady electrode/electrolyte interface. Herein, a simple one-step sintering process is developed, where vanadium−oxalate−phosphite/phosphate frameworks and fluorinated polymer are used to synthesize carbon-coated KVPO 4 F nanoplates. It is found that the V−F−C bond generated by fluorinated-polymer-derived carbon at the interface of KVPO 4 F/C nanoplates diminishes the F loss, as well as enhances K-ions migration ability and the electronic conductivity of KVPO 4 F. The as-synthesized KVPO 4 F/C cathode delivers a reversible capacity of 106.5 mAh g −1 at 0.2 C, a high working voltage of 4.28 V, and a rate capability with capacity of 73.8 mAh g −1 at the ultrahigh current density of 100 C. In addition, a KVPO 4 F/C//soft carbon full cell exhibits a high energy density of 235.5 Wh kg −1 .

Copper-based catalysts are widely explored in electrochemical CO2 reduction (CO2RR) because of their ability to convert CO2 into high-value-added multicarbon products. However, the poor stability and low selectivity limit the practical applications of these catalysts. Here, we proposed a simple and efficient asymmetric low-frequency pulsed strategy (ALPS) to significantly enhance the stability and the selectivity of the Cu-dimethylpyrazole complex Cu3(DMPz)3 catalyst in CO2RR. Under traditional potentiostatic conditions, Cu3(DMPz)3 exhibited poor CO2RR performance with the Faradaic efficiency (FE) of 34.5% for C2H4 and FE of 5.9% for CH4 as well as the low stability for less than 1 h. We optimized two distinguished ALPS methods toward CH4 and C2H4, correspondingly. The high selectivities of catalytic product CH4 (FECH4 = 80.3% and above 76.6% within 24 h) and C2H4 (FEC2H4 = 70.7% and above 66.8% within 24 h) can be obtained, respectively. The ultralong stability for 300 h (FECH4 > 60%) and 145 h (FEC2H4 > 50%) was also recorded with the ALPS method. Microscopy (HRTEM, SAED, and HAADF) measurements revealed that the ALPS method in situ generated and stabilized extremely dispersive and active Cu-based clusters (∼2.7 nm) from Cu3(DMPz)3. Meanwhile, ex situ spectroscopies (XPS, AES, and XANES) and in situ XANES indicated that this ALPS method modulated the Cu oxidation states, such as Cu(0 and I) with C2H4 selectivity and Cu(I and II) with CH4 selectivity. The mechanism under the ALPS methods was explored by in situ ATR-FTIR, in situ Raman, and DFT computation. The ALPS methods provide a new opportunity to boost the selectivity and stability of CO2RR.