查看更多>>摘要：Excavating highly efficient M-N-C electrocatalysts for electrochemical CO2 reduction (ECR) is of paramount importance. Herein, we report a single-atom Co-N-C catalyst (CoN4-CB) with a high CO Faradaic efficiency (FECO, 98.7%) in ECR comparable to that of a similarly prepared NiN4-CB catalyst. Impressively, CoN4-CB demonstrates a CO turnover frequency of 27173 h-1 and a CO current density of -33.6 mA center dot cm- 2 at -0.76 V, 20.2 and 6.8 times higher than that of NiN4-CB, respectively. In a solar-driven ECR system composed of a Si solar cell and a flow cell, CoN4-CB shows a remarkably large current density of 98.3 mA center dot cm- 2 with an average FECO of 92.1%. Theoretical calculations suggest that the energy barrier for *COOH formation largely decreases on CoN4 sites compared with NiN4 sites, leading to a low onset potential and high activity for CO production. This work will boost the development of efficient M-N-C electrocatalysts and further practical application of solar-driven ECR system.
查看更多>>摘要：Metal oxide semiconductors are promising for photosynthetic H2O2 & nbsp;production, provided the issue of excessive charge recombination can be adequately addressed. Inducing internal electric field is a common remedial strategy to inhibit carrier recombination but challenging to accomplish without external power input. To overcome this drawback, a novel photocathode was designed and fabricated by combing photothermoelectricity and photoelectricity by adding a NaCo2O4 film under the CuBi2O4 & nbsp;film to generate an internal electric field from photoinduced temperature gradients. Our results show the significantly enhanced photoelectrochemical activity for the composite photocathode with an H2O2 & nbsp;production concentration of 192.9 mu mol/L, 2.4 times higher than CuBi2O4 . Photocurrent under controlled temperature gradients and COMSOL simulation defined that the enhancement comes from the synergy of photothermoelectricity and photoelectricity. This work demonstrates a feasible strategy to inhibit carrier recombination in photoelectrode with internal thermoelectric potential, which can significantly enhance the energy conversion efficiency without extra energy consumption.
da Silva, Marcos A. R.Silva, Ingrid F.Xue, QiLo, Benedict T. W....
11页
查看更多>>摘要：Fe-N-C materials, when prepared as single-atom catalysts (SAC), display excellent activities in oxidation reactions. The systematic investigation of the iron coordination mode revealed that Fe-N4C catalysts are the most active for C-H bond oxidation. However, many of these catalysts are synthesized through pyrolysis, which is characterized by a lack of control and structures with heterogeneous composition, rarely presenting only atomically dispersed Fe-N-C as active sites. Herein, an alternative, reliable and easily reproducible method to obtain highly active Fe SACs (atomically dispersed) with Fe-N4 sites is presented, which is based on ion exchange of sodium from high crystalline sodium poly(heptazine imide) (Na-PHI) by other ions. The obtained catalyst can photocatalytically oxidize C-H bonds selectively toward ketones using only dioxygen. Detailed mechanism investigations indicate that the active species in the C-H bond oxidation are highly valent Fe(IV)/Fe(V)-oxo species, which are further activated by the holes generated at the PHI support under light irradiation.
查看更多>>摘要：Rational design and exploitation of efficient and inexpensive catalysts for water electrolysis are highly desired, yet very challenging. Herein, for the first time, we report a nanostructured catalyst of nickel phosphides ruthenium phosphides self-supported on nickel foam (Ni2P-Ru2P/NF) through an in situ growthphosphorization process. As expected, by virtue of prominent intrinsic activity, rich electrochemically active sites, and high electronic conductivity, the resultant Ni2P-Ru2P/NF exhibits enhanced electrocatalytic behavior for the oxygen evolution reaction and hydrogen evolution reaction, which delivers low overpotentials of 160 and 101 mV at 10 mA cm(-2) in alkaline media, respectively. Remarkably, the Ni2P-Ru2P/NF can dramatically accelerate full water splitting with an ultralow cell voltage of 1.45 V at 10 mA cm(-2), which far exceeds the benchmark Pt-C/NF//RuO2/NF (1.64 V) and ranks among the best electrocatalysts previously reported.
Karinshak, KyleChen, Pak WingLiu, Ru-FenGolden, Stephen J....
11页
查看更多>>摘要：The impacts of feed modulation (frequency, amplitude) and catalyst design (composition and architecture) parameters are reported for the conversion of methane and NOx over a dual-layer Pt+Pd/Al2O3 + Mn0.5Fe2.5O4/Al2O3 monolith. CH4 and NOx conversion data show that the dual-layer catalyst outperforms single-layer samples having the same catalyst loadings, with and without spinel. Close proximity of the PGM and MFO functions in the mixed-layer catalyst lowers the CH4 conversion at high temperature while separating the PGM and spinel layers with an intermediate Al2O3 layer does not. Methane conversion enhancement is linked to its nonmonotonic dependence on O-2. The performance gains are tied to a transient activity spike that occurs during the lean-to-rich feed transition when water is present in the feed. The transient spike is attributed to the removal of CO and H-2 products via reactions with stored O-2 in the spinel, eliminating inhibition of methane steam reforming.
查看更多>>摘要：Heterogeneous Fenton-reaction accomplishes the destruction of pollutants via the oxidation of hydroxyl radicals during water purification. Herein, two facet-engineered (control of different exposed crystal planes) BiOI nanocatalysts (BI-001 and BI-110) as the dual-reaction-center catalysts were loaded on the polyvinylidene fluoride membrane, remarkably accelerating the occurrence of Fenton-reaction and leading to the enhanced degradation of the pollutants in complex water matrices. The degradation efficiency of paracetamol by BI-110 membrane (~96.0%) was significantly higher than that of BI-001 membrane (~26.1%) in catalytic activity. The electron paramagnetic resonance tests and theoretical calculations proved that BI-110 possesses more oxygen vacancies, which acts as the electron-rich sites to trigger the Fenton-reaction. Correspondingly, the pollutants were adsorbed on the electron-poor Bi3+ sites and donate electrons during the degradation process. This study provides a candidate strategy to break the limitations of Fenton reaction advanced oxidation processes for water purification using the tunable facet-engineered BiOI membrane.
查看更多>>摘要：Solar-induced overall water splitting to produce hydrogen is inspiring towards energy sustainability, but it is also formidable due to its limited efficiency seriously hindering its scale up for practical application. CdS is an important transition metal sulfide with low-work-function. However, its photostability is often deteriorated due to photocorrosion influence. To overcome this issue, single-atom Pd was employed here to decorate CdS to form a CdS-Pd nanocatalyst through a simple and controllable photoinduced reduction strategy. The synergetic semiconductor (CdS)-metal (Pd) interaction promotes the fast bulk-to-surface electron migration, thereby the resultant CdS-Pd (3.83 parts per thousand) nanocatalyst shows considerable structural stability and dramatically improved solar induced HER activity in overall water splitting, about 110-fold higher than that of pristine CdS. Meanwhile, high apparent quantum yields (AQYs) of 4.47%/1.81% and 33.92%/27.49% were respectively achieved with this decorated nanocatalyst under the light of 420 nm/500 nm in absence and presence of scavenger, demonstrating the high-efficiency under broadband light illumination. Density functional theory (DFT) calculation supports that the easy formation of H* intermediates on the decorated nanocatalyst due to low energy barriers accounts for the internal promoted mechanism for hydrogen production. This study provides important insight to gain stable CdSbased photocatalysts for high-efficient hydrogen production by overall water splitting.
查看更多>>摘要：Chemical looping concept paves way toward intrinsically safe and efficient oxidative coupling of methane (CL-OCM) process, because it permits the reaction to proceed via repeating reduction-oxidation cycle in two reactors. It is calling for a ground-breaking catalyst with enough high selective CH4-converting lattice-oxygen carrying capacity but represents a grand challenge. Herein, we report an efficient catalyst obtainable by decorating an oxygen carrier FeMnO3 with Na2WO4, with good cycling performance, achieving a high space time yield of 29.8 g(C2-C3) kg(cat)(-1) h(-1) with 20% CH4 conversion and 80% C-2-C-3 selectivity at 800 degrees C and a low catalyst/CH4 weight ratio of 13.5. CL-OCM process is established by "FeMnO3. [MnFe2O4 + MnO]" redox cycle. Na2WO4-decoration gets lattice oxygen stored in FeMnO3 transformed from non-selective to selective due to mitigation of latticeoxygen evolution. Scaled up CL-OCM testing with 10-gram catalyst also yields comparable results seen in the case of using 1-gram catalyst, validating great application potential.
查看更多>>摘要：Graphitic carbon nitride (g-C3N4) is promising for photocatalytic conversion of greenhouse gas CO2 into valuable solar fuels. Crystalline g-C3N4 (CCN) attracts great attention, nevertheless, the CO2 reduction efficiency and selectivity are still dissatisfying, due to the lack of suitable active sites. In this study, tungsten doped CCN (CCN-W) is constructed by forming W-N6 bonding at the cavity sites of adjacent heptazine units. Significantly, relative to CCN, the full-spectrum CO2 reduction rate (11.91 mu mol g(-1) h(-1)) on CCN-W is increased by > 5 times, meanwhile, the photoelectron selectivity to hydrocarbons (CH4 and C2H4) approaching 83% is increased by > 2 times. The W6+-doping introduced W-N-6 as multifunctional active sites enrich both the photoelectrons and CO2 molecules, and catalyze their selective conversion into hydrocarbons by reducing reaction barrier and moder-ately stabilizing CO intermediates. This study will offer new insight into modulating the CCN photocatalysts with multifunctional active sites for efficient and selective photocatalytic CO2 reduction.
查看更多>>摘要：A NiCo2O4 catalyst was evaluated for CO + NO reaction under a photo-thermal synergistic effect. Compared with crystalline samples, metastable NiCo2O4 with a crystalline/amorphous heterostructure exhibited higher catalytic activity due to its better low temperature reducibility and more oxygen vacancies (VOs). The collective TPR, XPS, and in-situ DRIFTS results revealed that more VOs induced by CO directly interacting with the lattice oxygen of NiCo2O4 could promote NO adsorption and activation, and visible light irradiation further reinforced the above processes by facilitating CO to capture lattice oxygen and enriching electrons in VOs. With the increase in re -action temperature, the electron-rich VOs could further drive NO dissociation into N-2. Herein, the VOs was not only an active center of catalytic reaction, but also acted as a bridge between CO and NO for lattice oxygen circulation. Thus, a photo-thermal synergistic effect for NO reduction by CO occurred over metastable NiCo2O4.
NSTL
Elsevier