Ligand-Bound CO2 as a Nonclassical Route toward Efficient Photocatalytic CO2 Reduction with a Ni N-Confused Porphyrin.

Implementing the synergistic effects between the metal and the ligand has successfully streamlined the energetics for CO2 activation and gained high catalytic activities, establishing the important breakthroughs in photocatalytic CO2 reduction. Herein, we describe a Ni(II) N-confused porphyrin complex (NiNCP) featuring an acidic N-H group. It is readily deprotonated and exists in an anion form during catalysis. Owing to this functional site, NiNCP gave rise to an outstanding turnover number (TON) as high as 217,000 with a 98% selectivity for CO2 reduction to CO, while the parent Ni(II) porphyrin (NiTPP) was found to be nearly inactive. Our mechanistic analysis revealed a nonclassical reaction pattern where CO2 was effectively activated via the attack of the Lewis-basic ligand. The resulting ligand-bound CO2 adduct could be further reduced to produce CO. This new metal-ligand synergistic effect is anticipated to inspire the design of highly active catalysts for small molecule activations.

Accelerating Charge Kinetics in Photocatalytic CO2 Reduction by Modulating the Cobalt Coordination in Heterostructures of Cadmium Sulfide/Metal-Organic Layer.

Artificial photocatalytic CO2 reduction (CO2R) holds great promise to directly store solar energy into chemical bonds. The slow charge and mass transfer kinetics at the triphasic solid-liquid-gas interface calls for the rational design of heterogeneous photocatalysts concertedly boosting interfacial charge transfer, local CO2 concentration, and exposure of active sites. To meet these requirements, in this study heterostructures of CdS/MOL (MOL = metal-organic layer) furnishing different redox Co sites are fabricated for CO2R photocatalysts. It is found that the coordination environment of Co is key to photocatalytic activity. The best catalyst ensemble comprising ligand-chelated Co2+ with the bipyridine electron mediator demonstrates a high CO yield rate of 1523 µmol h-1 gcat -1, selectivity of 95.8% and TON of 1462.4, which are ranked among the best seen in literature. Comprehensive photochemical and electroanalytical characterizations attribute the high CO2R performance to the improved photocarrier separation and charge kinetics originated from the proper energy band alignment and coordination chemistry. This work highlights the construction of 2D heterostructures and modulation of transition metal coordination to expedite the charge kinetics in photocatalytic CO2 reduction.

Pulse Electrolysis Turns on CO2 Methanation through N-Confused Cupric Porphyrin.

Breaking the D4h symmetry in the square-planar M-N4 configuration of macrocycle molecular catalysts has witnessed enhanced electrocatalytic activity, but at the expense of electrochemical stability. Herein, we hypothesize that the lability of the active Cu-N3 motifs in the N-confused copper (II) tetraphenylporphyrin (CuNCP) could be overcome by applying pulsed potential electrolysis (PPE) during electrocatalytic carbon dioxide reduction. We find that applying PPE can indeed enhance the CH4 selectivity on CuNCP by 3 folds to reach the partial current density of 170 mA cm-2 at >60 % Faradaic efficiency (FE) in flow cell. However, combined ex situ X-ray diffraction (XRD), transmission electron microscope (TEM), and in situ X-ray absorption spectroscopy (XAS), infrared (IR), Raman, scanning electrochemical microscopy (SECM) characterizations reveal that, in a prolonged time scale, the decomplexation of CuNCP is unavoidable, and the promoted water dissociation under high anodic bias with lowered pH and enriched protons facilitates successive hydrogenation of *CO on the irreversibly reduced Cu nanoparticles, leading to the improved CH4 selectivity. As a key note, this study signifies the adaption of electrolytic protocol to the catalyst structure for tailoring local chemical environment towards efficient CO2 reduction.

Proton Shuttling by Polyaniline of High Brønsted Basicity for Improved Electrocatalytic Ethylene Production from CO2.

Hybrid organic/inorganic composites with the organic phase tailored to modulate local chemical environment at the Cu surface arise as an enchanting category of catalysts for electrocatalytic CO2 reduction reaction (CO2 RR). A fundamental understanding on how the organics of different functionality, polarity, and hydrophobicity affect the reaction path is, however, still lacking to guide rational catalyst design. Herein, polypyrrole (PPy) and polyaniline (PANI) manifesting different Brønsted basicity are compared for their regulatory roles on the CO2 RR pathways regarding *CO coverage, proton source and interfacial polarity. Concerted efforts from in situ IR, Raman and operando modelling unveil that at the PPy/Cu interface with limited *CO coverage, hydridic *H produced by the Volmer step favors the carbon hydrogenation of *CO to form *CHO through a Tafel process; Whereas at the PANI/Cu interface with concentrated CO2 and high *CO coverage, protonic H+ shuttled through the benzenoid -NH- protonates the oxygen of *CO, yielding *COH for asymmetric coupling with nearby *CO to form *OCCOH under favored energetics. As a result of the tailored chemical environment, the restructured PANI/Cu composite demonstrates a high partial current density of 0.41 A cm-2 at a maximal Faraday efficiency of 67.5 % for ethylene production, ranking among states of the art.

Robust Electrocatalytic CO2 Reduction in Acid Enabled by "Molecularly Charged" Cobalt Phthalocyanine: A Profound Understanding from Electric Double Layer.

Electrocatalytic CO2 reduction (eCO2R) in acid holds promise in renewable electricity-powered CO2 utilization with high efficiency, but the hydrogen evolution reaction (HER) often prevails and results in a low eCO2R selectivity. Here, using cobalt phthalocyanine/Ketjen black (CoPc/KB) as the model catalysts, we systematically study the effect of active site density, operational current density, and hydrated cations on the acidic eCO2R selectivity and decipher it through the componential dynamics of electric double layer (EDL). The optimal CoPc-4/KB demonstrates a near-unity CO Faradaic efficiency from 50 to 400 mA cm-2 and superb operational stability (>120 h) at 100 mA cm-2. Aided by in situ Raman and infrared spectroscopies, we reveal that the proper cations establish an electrostatic shield for mitigating bulk H+ penetration and mediate the interfacial water structure for suppressing HER. This study should elicit further profound thinking on robust eCO2R system design from the perspective of multiphasic and dynamic EDL.

A "Trinity" Design of Li-O2 Battery Engaging the Slow-Release Capsule of Redox Mediators.

Nonaqueous Li-O2 battery (LOB) represents one of the promising next-gen energy storage solutions owing to its ultrahigh energy density but suffers from problems such as high charging overpotential, slow redox kinetics, Li anode corrosion, etc., calling for a systemic optimization of the battery configuration and structural components. Herein, an ingenious "trinity" design of LOB is initiated by implementing a hollowed cobalt metal organic framework (MOF) impregnating iodized polypyrrole simultaneously as the cathode catalyst, anode protection layer, and slow-release capsule of redox mediators, so as to systemically address issues of impeded mass transport and redox kinetics on the cathode, dendrite growth, and surface corrosion on the anode, as well as limited intermediate solubility in the low donor-number (DN) solvent. As a result of the systemic effort, the LOB constructed demonstrates an ultralow discharge/charge polarization of 0.2 V, prolonged cycle life of 1244 h and total discharge capacity of 28.41 mAh cm-2 . Mechanistic investigations attribute the superb LOB performance to the redox-mediated solution growth mechanism of crystalline Li2 O2 with both enhanced reaction kinetics and reversibility. This study offers a paradigm in designing smart materials to raise the performance bar of Li-O2 battery toward realistic applications.

Proteomic analysis identifies HMGA2 as a novel biomarker of overall survival in papillary renal cell carcinoma.

PURPOSE: Although papillary renal cell carcinoma (PRCC) has a relatively favorable prognosis, a small number of patients with lymph node or distant metastasis have a poor prognosis. Owing to the complex typing and heterogeneity of PRCC, it remains difficult to provide risk stratification. The objective of our research was to identify potential markers of PRCC prognosis. METHODS: We performed proteomics and bioinformatics analyses on six pairs of formalin-fixed paraffin-embedded tumor and paired normal tissue samples. The Cancer Genome Atlas (TCGA) data were used to analyze the prognostic value of differentially expressed proteins (DEPs) in PRCC. We verified the expression of the major biomarker through immunohistochemistry (IHC) in 91 PRCC tumor specimens. RESULTS: Proteomic analysis revealed 1544 DEPs between tumor and paired normal tissues. PRCC transcriptomic data from the TCGA database revealed that compared to non-tumor tissues, the expression of high-mobility group protein A2 (HMGA2) was upregulated in tumor tissues, and patients with high HMGA2 expression exhibited shorter overall survival times. HMGA2 was associated with PRCC tissue subtype and higher cell pleomorphism. Both TCGA and IHC results showed that HMGA2 expression was associated with lymph node metastasis and clinical stage. CONCLUSION: HMGA2 was positively correlated with malignant progression and could be a valuable novel prognostic biomarker for PRCC risk stratification.