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Owing to a large band gap and high surface energy determined via theoretical calculation, anatase TiO2 with dominant (211) facets can be expected to serve as one of the candidates for inorganic photoanode materials. Unfortunately, high-energy (211) surfaces containing four- and five-coordinated Ti atoms usually diminish rapidly during the crystal growth by a thermal process as a result of the minimization of surface energy. Here we report a successful preparation of an anatase TiO2 photoanode with dominant (211) facets on various substrates by magnetron sputtering technology. The proposed formation mechanism of (211) facets is derived from the competition between high-energy ion impinging and thermodynamics in the deposition process. The TiO2 photoanode with over 1 μm thickness yields a record charge-separation efficiency of ∼54.4% at 0.46 V versus the reversible hydrogen electrode, corresponding to a photocurrent density of ∼0.32 mA cm−2. The photogenerated charge carriers are directionally separated within the crystal grains by the internal magnetic field and quickly transported on the (211) surfaces with unsaturated coordination sites. Most importantly, we find that the photoanode simultaneously integrates flexible, hard and lubricant effects into photoelectrochemical behaviors, leading to long-term stable operation (over 1100 h), good durability with a low wear rate, and facile bendability (similar performance before and after bending). We also fabricate a large-area (10 × 10 cm2) photoanode and use it in an unbiased photoelectrochemical device, further suggesting its scaling and practical potential. [ABSTRACT FROM AUTHOR]

Correction for 'Atomically dispersed cobalt on graphitic carbon nitride as a robust catalyst for selective oxidation of ethylbenzene by peroxymonosulfate' by Jiaquan Li et al., J. Mater. Chem. A, 2021, 9, 3029–3035, https://doi.org/10.1039/D0TA11503G. [ABSTRACT FROM AUTHOR]

Despite considerable progress in the field of sustainable ammonia technology, the low efficiency and yield have remained the main bottleneck in artificial nitrogen fixation under ambient conditions. In this work, an ultrathin carbon quantum dot modified hydrogenated mesoporous SrTiO3 heterostructure (CQDs/STO) has been developed as a bifunctional catalyst for enhanced nitrogen reduction. CQDs/STO exhibits a high photocatalytic activity and an ammonia yield of 143 μmol g−1 h−1 has been achieved without any sacrificial reagent, which is about 7 times that of STO nanoparticles. Furthermore, we demonstrate that CQDs/STO can be utilized as a bifunctional catalyst for cascade photoelectrochemical nitrogen reduction, resulting in a ∼50% increase in the ammonia yield. DFT calculations reveal that the synergy between SrTiO3 and CQDs has the capability for photocatalytic reduction of N2 with the O-vacancies in SrTiO3 playing a key role also as electrocatalytic centers. We believe that such a cascade catalytic system provides a new insight into designing photoelectrochemical devices for solar-driven nitrogen fixation. [ABSTRACT FROM AUTHOR]

Nanostructure is the most important aspect in the development of high performance supercapacitors. In this work, we designed and developed new one-dimensional hierarchical hollow nickel–cobalt layered double hydroxide nanocages assembled on MnO2 nanotubes with uniformly dispersed CoS2 nanoparticles, MnO2@NiCo-LDH/CoS2, using a zeolitic imidazolate skeleton (ZIF-67) as the template via multiple hydrothermal and sulfuration processes. This unique one-dimensional hierarchical nanostructure is characterized by a high specific area and high structural stability. The presence of CoS2 nanoparticles in the nanocage increases the electrical conductivity and enhances the stability of the structure. Electrochemical studies show that MnO2@NiCo-LDH/CoS2 electrode materials have a high specific capacitance of 1547 F g−1 at a current density of 1 A g−1 and 1189 F g−1 at 10 A g−1, exhibiting high rate performance (76.9%) and high stability (82.3%), which is substantially better than the performance of most recently reported similar systems. The asymmetric supercapacitor assembled with MnO2@NiCo-LDH/CoS2 and activated carbon has a maximum energy density of 50 W h kg−1 and a maximum power density of 9658 W kg−1. The unique nanostructure and excellent performance of the asymmetric supercapacitor in the present study demonstrate a new platform for developing highly efficient supercapacitor materials with high energy density and high power density. [ABSTRACT FROM AUTHOR]

La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) solid oxide fuel cell cathodes were poisoned by Cr at different temperatures and polarization conditions with a Cr–Fe alloy as the interconnect. Cr induced degradation was analysed by electrochemical impedance spectroscopy (EIS) focusing on the electrochemical resistance (Rchem) that reflects the cathode electrochemical properties. It was found that Rchem increased more with increasing temperatures. However cathodic polarization exhibited a synergistic effect with the temperature, which accelerated the LSCF cathode degradation at 800 °C while lowering the degree of degradation at 900 °C. By correlating complementary micro- and nano-scale microstructure characterization with the impedance analysis, the degradation mechanisms were investigated. A new Cr incorporation mechanism involving preferential formation of nanometre size Fe–Co–Cr–O spinel particles within the cathode up to the cathode/electrolyte interface was found to be responsible for the reduced degradation at 900 °C combined with cathodic polarization. The new mechanism reveals that the activity of B site elements in LSCF and possibly other perovskite cathodes plays an important role under certain combined temperature and polarization conditions, therefore future research in designing Cr resistant perovskite cathode materials may consider strategies that utilize the exsolution of B site elements for the formation of beneficial spinel phases. [ABSTRACT FROM AUTHOR]

Metal-oxide nanoclusters (NCs) such as FeOx, CoOx, and NiOx are incorporated into iron phthalocyanine (FePc) supported on graphene, MOx/FePc, via a facile self-assembly method. MOx/FePc electrocatalysts show high activity, selectivity and stability for the electrochemical CO2 reduction reaction (CO2RR) as compared with the corresponding metal phthalocyanines, i.e., FePc, CoPc and NiPc, under identical test conditions. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy reveals that MOx/FePc undergoes a metal ion replacement of the iron center of Pc, forming electrochemically substituted metal Pc, e-MPc where M = Co and Ni, co-existing with the replaced FeOx nanoparticles (NPs) in the vicinity of the e-MPc. The results indicate that the e-MPc with in situ dispersed FeOx NPs, FeOx/e-CoPc and FeOx/e-NiPc exhibits excellent activity, high selectivity and stability for the CO2RR. [ABSTRACT FROM AUTHOR]

Bismuth based oxides have excellent ionic conductivity and fast oxygen surface kinetics and show promising potential as highly active electrode materials in solid oxide cells (SOCs) such as solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs). However, the low melting temperature and high activity of bismuth based oxides severely limit their wide applications in SOCs. Herein, we successfully synthesized a 40 wt% Er0.4Bi1.6O3 decorated La0.76Sr0.19MnO3+δ (ESB–LSM) electrode via a new gelation method and directly assembled it on a Ni–yttria-stabilized zirconia (Ni–YSZ) cermet supported YSZ electrolyte cell without the conventional high temperature pre-sintering step. ESB decoration substantially enhances the electrocatalytic activity of the LSM electrode for the oxygen reduction/evolution reactions (ORR/OER). A YSZ electrolyte cell with the directly assembled ESB–LSM electrode exhibits a peak power density of 1.62 W cm−2 at 750 °C, significantly higher than 0.48 and 0.88 W cm−2 obtained on cells with a directly assembled pristine LSM and LSM–YSZ composite electrode, respectively. Most importantly the cells with the directly assembled ESB–LSM oxygen electrodes show excellent stability in SOFC, SOEC and reversible SOC operating modes for over 200 h. The present study demonstrates a significant advancement in the development of bismuth based oxide decorated high performance and stable oxygen electrodes for reversible SOCs. [ABSTRACT FROM AUTHOR]

It is highly desirable but challenging to develop a highly active as well as durable bifunctional electrocatalyst for the reversible oxygen reduction reaction and evolution reaction (ORR & OER). Here a new class of bifunctional oxygen electrocatalysts has been developed based on ultrafine transition metal-oxide nanoparticles (NPs), such as NiO, FeO or NiFeO, embedded in an amorphous MnOx shell, where the embedded NP core contributes to the high OER activity and the porous amorphous MnOx shell functions as an effective ORR catalyst as well as providing effective structural confinement to the metal-oxide NP core. The best performance was obtained for NiFeO@MnOx, exhibiting a potential gap, ΔE, of 0.798 V to achieve a current of 3 mA cm−2 for the ORR and 5 mA cm−2 for the OER in 0.1 M KOH solution, better than that of Ir/C (0.924 V) and Pt/C (1.031 V). Most importantly, NiFeO@MnOx shows superior stability due to the outstanding structural confinement effect of the amorphous MnOx, achieving a ΔE of 0.881 V after 300 cycles, outperforming 1.093 V obtained for the state-of-the-art Ir–Pt/C oxygen electrocatalysts. [ABSTRACT FROM AUTHOR]

An oxygen electrode finds many applications in various electrochemical energy conversion devices such as fuel cells and metal–air batteries. Highly efficient gas–proton transportation at the electrode is very important to enhance the power density of these devices. Herein, we report the construction of a highly efficient oxygen electrode with substantially improved proton conductivity and gas transportation properties using three dimensionally ordered macroporous Nafion/Cs2.5H0.5PW12O40, 3DOM Nafion/CsHPW, scaffold supported Pt/C nanocomposites. The best results were obtained for cells with 3DOM Nafion/CsHPW with 10% CsHPW, achieving a maximum power density of 955 mW cm−2, 31% higher than 730 mW cm−2 for the cell with the conventional Nafion-binder based oxygen electrode. The proton conductivity of the 10% 3DOM Nafion/CsHPW catalyst layer is 1.56 × 10−2 S cm−1, 112% higher than 7.35 × 10−3 S cm−1 measured for the conventional catalyst layer with the Nafion binder. The results demonstrate the significant advantages of the oxygen electrodes with the Pt/C-3DOM Nafion/CsHPW architecture over the conventional Nafion-binder based ones, with the significantly enhanced proton conductivity of uniformly distributed CsHPW nanoparticles (NPs) and much better gas diffusion properties of the 3DOM architecture. [ABSTRACT FROM AUTHOR]

The co-doped lanthanum silicate oxyapatites, La9.5A0.5Si5.5Fe0.5O26.5 (A = Ba, Sr, and Ca), are synthesized by the high-temperature solid state reaction process. The phase formation and structure properties of undoped lanthanum silicate oxyapatite (La9.67Si6O26.5, LSO), Fe-doped lanthanum silicate oxyapatite (La10Si5FeO26.5, LSFO) and co-doped lanthanum silicate oxyapatites (La9.5A0.5Si5.5Fe0.5O26.5, A = Ba, Sr, and Ca) are characterized by X-ray diffraction (XRD) and scanning electron spectroscopy (SEM). The effect of co-doping of A (A = Ba, Sr, Ca) and Fe on the microstructure, sinterability and oxide ion conductivity of lanthanum silicate oxyapatites is investigated in detail. The results show that, as compared to LSO and LSFO oxyapatites, co-doping of A (A = Ba, Sr, and Ca) and Fe significantly benefits the sintering and densification process, and enhances the oxide ion conductivity. For co-doped oxyapatites, the oxide ion conductivities are related to the dopant size, the best properties are obtained for the oxyapatite co-doped with Ca and Fe. The co-doped La9.5Ca0.5Si5.5Fe0.5O26.5 (LCSFO) oxyapatite is a good electrolyte for SOFCs, with an oxide ion conductivity of 1.39 × 10−2 S cm−1 at 800 °C and a low activation energy of 90.71 kJ mol−1. The bulk density and oxide ion conductivities of co-doped oxyapatite ceramics increase significantly with the increase of the sintering temperature. The grain bulk and grain boundary resistances of La9.5Ba0.5Si5.5Fe0.5O26.5 (LBSFO), La9.5Sr0.5Si5.5Fe0.5O26.5 (LSSFO) and LCSFO oxyapatite ceramics are significantly smaller than those of LSO and LSFO oxyapatite ceramics sintered under the identical conditions. [ABSTRACT FROM AUTHOR]

A comprehensive strategy has been developed to synthesize highly ordered mesoporous Nafion membranes with different structure symmetries including 2D hexagonal (2D-H), 3D face-centered (3D-FC), 3D cubic-bicontinuous (3D-CB) and 3D body-centered (3D-BC), using a soft template method with the assistance of a silica colloidal mediator. The Nafion membrane derived from the self-assembled mesoporous Nafion–silica composites maintained the microstructures of the silica framework, which was confirmed by small angle X-ray scattering (SAXS) and TEM. The in situ time-resolved synchrotron SAXS clearly indicates that the presence of silica colloids is critical for the formation of the highly ordered mesoporous structured phase in the precursor solution. The best results are observed on Nafion membranes with 2D-H structure in terms of proton conductivity and cell performance under reduced relative humidity (RH) conditions, achieving proton conductivities of 0.08, 0.062 and 0.038 S cm−1 at 100, 40 and 0%RH, respectively. Moreover, the power output of the mesoporous Nafion membrane cells show a S-shaped dependence on RH and are stable under anhydrous conditions (i.e., 0% RH), demonstrating the outstanding high water retention capability of the mesoporous structure of the membranes. [ABSTRACT FROM AUTHOR]

Borosilicate-based glasses are the most common sealant materials for solid oxide fuel cells (SOFCs). However, boron species vaporizing from glass sealants poison and degrade the electrocatalytic activity of cathodes of SOFCs. In this study, we report the development of a new class of glass sealants based on bismuth and zinc doped borosilicates with significantly suppressed boron volatility. Doping Bi induces the [BO3] → [BO4] transition with an increased binding energy of boron, while addition of Zn leads to the formation of a boron-containing compound, Sr3B2SiO8, with significantly increased stability of boron in the glass matrix. Using La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) perovskite oxide as the cathode to assess the boron deposition and poisoning, the results indicate that the polarization performance of the LSCF cathode for the O2 reduction reaction in the presence of Bi and Zn doped glass is very stable with a negligible change in the microstructure of the electrodes. In contrast, in the case of conventional borosilicate glass, boron preferentially deposits in the electrode/electrolyte region under cathodic polarization, forming primarily LaBO3, disintegrating the perovskite structure and significantly degrading the electrochemical activity of the LSCF cathodes. Doping Bi or Zn remarkably reduces the boron volatility of the glass, thus effectively inhibiting the poisoning of boron species on the microstructure and electrocatalytic activity of SOFC cathodes such as LSCF. The present results demonstrate for the first time that the Bi and Zn doping is the most effective strategy to minimize the boron poisoning from the source by suppressing the boron vaporization of borosilicate-based glass sealant materials. [ABSTRACT FROM AUTHOR]

A novel active graphene-like nanosheet (AGN) with a high specific surface area is first developed as an efficient electrocatalyst support synthesized through an efficient ion-exchange-assisted synthesis route. The AGN shows high electronic conductivity and strong cohesive force and distribution effects toward the catalyst nanoparticles. The AGN supported PdxPty bimetallic catalyst system with ultralow Pt loading exhibits excellent catalytic performance and superb durability for the oxygen reduction reaction of fuel cells, giving a high mass activity of 1930 mA mgPt-1 at 0.9 V vs. RHE. [ABSTRACT FROM AUTHOR]

A nitrogen and phosphorus-dual-doped carbon nanotube (N, P-CNT) array has been successfully synthesized by a novel one-pot method, using an aminophosphonic acid resin as the N, P and C sources. The N, P-CNTs are open with large inner channels, allowing oxygen molecules to access a large number of catalytically active sites on the inner walls. The N, P-CNTs are not only comparable to Pt/C in electrocatalytic activity for the oxygen reduction reaction (ORR) in 0.1 M KOH, but are also highly stable and tolerant to methanol and CO poisoning. An onset potential of 0.95 V close to that of Pt/C and a well-defined limiting current plateau for the ORR are observed. Moreover, there is almost no visible current density decrease on N, P-CNTs after 5000 cycles. [ABSTRACT FROM AUTHOR]

There are significant technological and economical advantages for operating a proton exchange membrane fuel cell (PEMFC) at temperatures above 100-150 °C. One of the key components in the development of high temperature PEMFCs is the proton exchange membrane (PEM). The PEM not only needs to be highly stable in the harsh chemical and physical environment in fuel cells, but also needs to possess high proton conductivity at elevated temperatures and under low humidity conditions. In this paper, the research activity and progress in the development of high temperature PEMs will be briefly reviewed but the main emphasis will be on the development of unsupported and functionalized nano and mesoporous structured inorganic materials such as TiO[sub 2], Fe[sub 2]O[sub 3], Al[sub 2]O[sub 3] and SiO[sub 2] as high temperature PEMs for fuel cells. Among various inorganic proton conducting materials, heteropolyacid (e.g., H[sub 3]PW[sub 12]O[sub 40] or HPW) functionalized mesoporous silica, HPW-meso-silica, shows particularly promising potential as new PEMs for fuel cells. The challenge and prospects of the development of functionalized mesoporous silica based PEMs for fuel cells operated at high temperatures (300-450 °C) are discussed. [ABSTRACT FROM AUTHOR]

The sluggish water oxidation reaction represents a significant challenge in water splitting for energy storage using hydrogen. We herein report the synthesis of MnO2 nanowires with the ultrasmall diameter and aspect ratio as high as 125 on graphene using a novel in situ polymer-mediated self-assembly approach in aqueous solution and under ambient conditions. The self-assembly process is simple and controllable by the concentration and pH of the polymer solution, in which the polymer serves as a soft template to direct the growth of MnO2 nanowires and also stabilize the structure, forming a unique graphene supported MnO2 nanowire, G@MnO2 NW. This nanostructure shows the most significant improvement of the catalytic activity compared to the graphene supported MnO2 nanoparticle and commercial Pt/C toward water oxidation under both alkaline and neutral conditions, and demonstrates for the first time a remarkable effect of the shape of MnO2 nanostructures on water oxidation catalysis. For example, at 0.7 V, it produces a current density of 5.9 mA cm−2, 14.8 times that of the graphene supported MnO2 nanoparticle (4.0 mA cm−2) and 8.4 times that of Pt/C (0.7 mA cm−2) in alkaline solution. Furthermore, it displays the highest turnover frequency reported among all the Mn oxides used for water oxidation catalysis. The G@MnO2 NW shows great potential as a water oxidation catalyst for energy storage applications. [ABSTRACT FROM AUTHOR]