3D Conjugated Hole Transporting Materials for Efficient and Stable Perovskite Solar Cells and Modules.

The orthogonal structure of the widely used hole transporting material (HTM) 2,2',7,7'-tetrakis(N, N-di-p-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD) imparts isotropic conductivity and excellent film-forming capability. However, inherently weak intra- and inter-molecular π-π interactions result in low intrinsic hole mobility. Herein, a novel HTM, termed FTPE-ST, with a twist conjugated dibenzo(g,p)chrysene core and coplanar 3,4-ethylenedioxythiophene (EDOT) as extended donor units, is designed to enhance π-π interactions, without compromising on solubility. The three-dimensional (3D) configuration provides the material multi-direction charge transport as well as excellent solubility even in 2-methylanisole, and its large conjugated backbone endows the HTM with a high hole mobility. Moreover, the sulfur donors in EDOT units coordinate with lead ions on the perovskite surface, leading to stronger interfacial interactions and the suppression of defects at the perovskite/HTM interface. As a result, perovskite solar cells (PSCs) employing FTPE-ST achieve a champion power conversion efficiency (PCE) of 25.21% with excellent long-time stability, one of the highest PCEs for non-spiro HTMs in n-i-p PSCs. In addition, the excellent film-forming capacity of the HTM enables the fabrication of FTPE-ST-based large-scale PSCs (1.0 cm2) and modules (29.0 cm2), which achieve PCEs of 24.21% (certificated 24.17%) and 21.27%, respectively.

Monolithic FAPbBr3 photoanode for photoelectrochemical water oxidation with low onset-potential and enhanced stability.

Despite considerable research efforts on photoelectrochemical water splitting over the past decades, practical application faces challenges by the absence of efficient, stable, and scalable photoelectrodes. Herein, we report a metal-halide perovskite-based photoanode for photoelectrochemical water oxidation. With a planar structure using mesoporous carbon as a hole-conducting layer, the precious metal-free FAPbBr3 photovoltaic device achieves 9.2% solar-to-electrical power conversion efficiency and 1.4 V open-circuit voltage. The photovoltaic architecture successfully applies to build a monolithic photoanode with the FAPbBr3 absorber, carbon/graphite conductive protection layers, and NiFe catalyst layers for water oxidation. The photoanode delivers ultralow onset potential below 0 V versus the reversible hydrogen electrode and high applied bias photon-to-current efficiency of 8.5%. Stable operation exceeding 100 h under solar illumination by applying ultraviolet-filter protection. The photothermal investigation verifies the performance boost in perovskite photoanode by photothermal effect. This study is significant in guiding the development of photovoltaic material-based photoelectrodes for solar fuel applications.

Dynamic Surface Reconstruction of Amphoteric Metal (Zn, Al) Doped Cu2 O for Efficient Electrochemical CO2 Reduction to C2+ Products.

The recognition of the surface reconstruction of the catalysts during electrochemical CO2 reduction (CO2RR) is essential for exploring and comprehending active sites. Although the superior performance of Cu-Zn bimetallic sites toward multicarbon C2+ products has been established, the dynamic surface reconstruction has not been fully understood. Herein, Zn-doped Cu2 O nano-octahedrons are used to investigate the effect of the dynamic stability by the leaching and redeposition on CO2RR. Correlative characterizations confirm the Zn leaching from Zn-doped Cu2 O, which is redeposited at the surface of the catalysts, leading to dynamic stability and abundant Cu-Zn bimetallic sites at the surface. The reconstructed Zn-doped Cu2 O catalysts achieve a high Faradaic efficiency (FE) of C2+ products (77% at -1.1 V versus reversible hydrogen electrode (RHE)). Additionally, similar dynamic stability is also discovered in Al-doped Cu2 O for CO2RR, proving its universality in amphoteric metal-doped catalysts. Mechanism analyses reveal that the OHC-CHO pathway can be the C-C coupling processes on bare Cu2 O and Zn-doped Cu2 O, and the introduction of Zn to Cu can efficiently lower the energy barrier for CO2RR to C2 H4 . This research provides profound insight into unraveling surface dynamic reconstruction of amphoteric metal-containing electrocatalysts and can guide rational design of the high-performance electrocatalysts for CO2RR.

Efficient urea electrosynthesis from carbon dioxide and nitrate via alternating Cu-W bimetallic C-N coupling sites.

Electrocatalytic urea synthesis is an emerging alternative technology to the traditional energy-intensive industrial urea synthesis protocol. Novel strategies are urgently needed to promote the electrocatalytic C-N coupling process and inhibit the side reactions. Here, we report a CuWO4 catalyst with native bimetallic sites that achieves a high urea production rate (98.5 ± 3.2 µg h-1 mg-1cat) for the co-reduction of CO2 and NO3- with a high Faradaic efficiency (70.1 ± 2.4%) at -0.2 V versus the reversible hydrogen electrode. Mechanistic studies demonstrated that the combination of stable intermediates of *NO2 and *CO increases the probability of C-N coupling and reduces the potential barrier, resulting in high Faradaic efficiency and low overpotential. This study provides a new perspective on achieving efficient urea electrosynthesis by stabilizing the key reaction intermediates, which may guide the design of other electrochemical systems for high-value C-N bond-containing chemicals.

Surface Reconstruction and Passivation of BiVO4 Photoanodes Depending on the "Structure Breaker" Cs.

Monoclinic BiVO4 is one of the most promising photoanode materials for solar water splitting. The photoelectrochemical performance of a BiVO4 photoanode could be significantly influenced by the noncovalent interactions of redox-inert metal cations at the photoanode-electrolyte interfaces, but this point has not been well investigated. In this work, we studied the Cs+-dependent surface reconstruction and passivation of BiVO4 photoanodes. Owing to the "structure breaker" nature of Cs+, the Cs+ at the BiVO4 photoanode-electrolyte interfaces participated in BiVO4 surface photocorrosion to form a Cs+-doped bismuth vanadium oxide amorphous thin layer, which inhibited the continuous photocorrosion of BiVO4 and promoted surface charge transfer and water oxidation. The resulting cocatalyst-free BiVO4 photoanodes achieved 3.3 mA cm-2 photocurrent for water oxidation. With the modification of FeOOH catalysts, the photocurrent at 1.23 VRHE reached 5.1 mA cm-2, and a steady photocurrent of 3.0 mA cm-2 at 0.8 VRHE was maintained for 30 h. This work provides new insights into the understanding of Cs+ chemistry and the effects of redox-inert cations at the electrode-electrolyte interfaces.

Iron atomic cluster supported on Co/NC having superior water oxidation activity over iron single atom.

Carbon-supported iron-cobalt bimetallic electrocatalysts usually exhibit robust catalytic activity toward the oxygen evolution reaction (OER). However, the spatial isolation of Fe species at atomic level on cobalt-carbon solid remains a great challenge for practical catalytic applications in the OER. Here, we report the fabrication of CoFe bimetal porous carbon electrocatalysts by pyrolysis of molecularly defined iron complexes such as FePc (Pc = phthalocyanine) and Fe(acac)3 pre-encapsulated in the cavities of zeolitic imidazolate framework (ZIF)-67. With this unique strategy, high-loading atomic Fe nanoclusters (Fe-ACs) and Fe single atoms (Fe-SAs) were supported on Co/NC hybrids relying on the size of the molecular Fe precursors. The former exhibited superior OER performance to the single Fe atom-decorated Co/NC, as well as other ZIF-67-derived electrocatalysts. Theoretical modulation suggests Co as the OER active site for Fe-ACs@Co/NC at the in situ-formed FeOOH-ACs/Co3O4 interface, while Fe was proposed as the active site for Fe-SAs@Co/NC.

Highly Efficient Biomass Upgrading by a Ni-Cu Electrocatalyst Featuring Passivation of Water Oxidation Activity.

Electricity-driven organo-oxidations have shown an increasing potential recently. However, oxygen evolution reaction (OER) is the primary competitive reaction, especially under high current densities, which leads to low Faradaic efficiency (FE) of the product and catalyst detachment from the electrode. Here, we report a bimetallic Ni-Cu electrocatalyst supported on Ni foam (Ni-Cu/NF) to passivate the OER process while the oxidation of 5-hydroxymethylfurfural (HMF) is significantly enhanced. A current density of 1000 mA cm-2 can be achieved at 1.50 V vs. reversible hydrogen electrode, and both FE and yield keep close to 100 % over a wide range of potentials. Both experimental results and theoretical calculations reveal that Cu doping impedes the OH* deprotonation to O* and hereby OER process is greatly passivated. Those instructive results provide a new approach to realizing highly efficient biomass upgrading by regulating the OER activity.

Highly Stable and Efficient Oxygen Evolution Electrocatalyst Based on Co Oxides Decorated with Ultrafine Ru Nanoclusters.

Exploring highly active and durable electrocatalysts for oxygen evolution reaction (OER) is significant to achieve efficient anion exchange membrane (AEM) water electrolysis. Herein, hollow Co-based N-doped porous carbon spheres decorated with ultrafine Ru nanoclusters (HS-RuCo/NC) are reported as efficient OER electrocatalysts via the pyrolysis of carboxylate-terminated polystyrene-templated bimetallic zeolite imidazolate frameworks accommodating Ru (III) ions. The unique hollow structure with hierarchically porous characteristics contributes to the electrolyte penetration for fast mass transport and the exposure of more metal sites. Theoretical and experimental studies reveal the synergistic effect between the in situ formed RuO2 and Co3 O4 as another critical factor for the high OER performance, where the coupling of RuO2 with Co3 O4 can optimize the electronic configuration of RuO2 /Co3 O4 heterostructure and decrease the energy barrier during OER. Meanwhile, the presence of Co3 O4 can efficiently suppress the over-oxidation of RuO2 , endowing the catalysts with high stability. As expected, when the resultant HS-RuCo/NC was integrated into an AEM water electrolyzer, the obtained electrolyzer exhibits a cell voltage of 2.07 V to launch the current density of 1 A cm-2 and excellent long-term stability at 500 mA cm-2 under room temperature in alkaline solution, outperforming the commercial RuO2 -based AEM water electrolyzer (2.19 V).

Sacrificial W Facilitates Self-Reconstruction with Abundant Active Sites for Water Oxidation.

Water oxidation is an important reaction for multiple renewable energy conversion and storage-related devices and technologies. High-performance and stable electrocatalysts for the oxygen evolution reaction (OER) are urgently required. Bimetallic (oxy)hydroxides have been widely used in alkaline OER as electrocatalysts, but their activity is still not satisfactory due to insufficient active sites. In this research, A unique and efficient approach of sacrificial W to prepare CoFe (oxy)hydroxides with abundant active species for OER is presented. Multiple ex situ and operando/in situ characterizations have validated the self-reconstruction of the as-prepared CoFeW sulfides to CoFe (oxy)hydroxides in alkaline OER with synchronous W etching. Experiments and theoretical calculations show that the sacrificial W in this process induces metal cation vacancies, which facilitates the in situ transformation of the intermediate metal hydroxide to CoFe-OOH with more high-valence Co(III), thus creating abundant active species for OER. The Co(III)-rich environment endows the in situ formed CoFe oxyhydroxide with high catalytic activity for OER on a simple flat glassy carbon electrode, outperforming those not treated by the sacrificial W procedure. This research demonstrates the influence of etching W on the electrocatalytic performance, and provides a low-cost means to improve the active sites of the in situ self-reconstructed bimetallic oxyhydroxides for OER.

In-Situ Generated CsPbBr3 Nanocrystals on O-Defective WO3 for Photocatalytic CO2 Reduction.

Metal halide perovskite (MHP) nanocrystals (NCs) have shown promising application in photocatalytic CO2 reduction, but their activities are still largely restrained by severe charge recombination and narrow solar spectrum response. Assembly of heterojunctions can be beneficial to the charge separation in MHPs while the assembly process usually brings native interfacial defects, impeding efficient charge separation between two materials. Herein, an in-situ generation strategy was developed to prepare CsPbBr3 /WO3 heterojunction, using WO3 nanosheets (NSs) as growing substrate for the growth of CsPbBr3 NCs. The developed CsPbBr3 /WO3 heterojunction exhibited a high-quality interface, greatly facilitating charge transfer between two semiconductors. The hybrid photocatalyst displayed an excellent activity toward CO2 reduction, which was about 7-fold higher than pristine CsPbBr3 NCs and 3.5-fold higher than their assembled counterparts. The experimental results and theoretical simulations revealed that a Z-scheme mechanism with a favorable internal electric field was responsible for the good performance of CsPbBr3 /WO3 heterojunction. By using O-defective WO3 NSs as a near-infrared (NIR) light absorber, the CsPbBr3 /WO3 heterojunction could harvest NIR light and showed an impressive activity toward CO2 reduction. This work demonstrates a new strategy to design MHP-based heterojunctions by synergistically considering the interface quality, charge transfer mode, interfacial electric field, and light response range between two semiconductors.

Unraveling the Photogenerated Electron Localization on the Defect-Free CH3NH3PbI3(001) Surfaces: Understanding and Implications from a First-Principles Study.

The localization of photogenerated electrons in photovoltaic and photocatalytic materials is crucial for reducing the electron-hole recombination rate. Here, the photogenerated electron localization is systematically investigated on the CH3NH3PbI3 (MAPbI3) perovskite using first-principles calculations. It is found that under vacuum conditions, the photogenerated electron is delocalized in the MAPbI3 bulk as well as on the stochiometric MAPbI3(001) surface with the CH3NH3I (MAI) termination, while it is trapped on the defect-free PbI2-terminated surface. Our ab initio molecular dynamics simulations reveal that the introduction of solutions will prompt the formation of localized electronic states. The photogenerated electron is discovered to be localized on both the MAI- and PbI2-terminated surfaces in the presence of solutions with different concentrations of HI, from pure water to the saturated solution. We demonstrate that the Pb-I bond weakening or breaking resulting in an unsaturated coordination of a Pb site is the prerequisite to trap the photogenerated electron.

Achieving rational design of alloy catalysts using a descriptor based on a quantitative structure-energy equation.

An approach to rationally design optimal alloy catalysts is established using nitric oxide (NO) oxidation as an example. We introduce a quantitative structure-energy equation to predict the chemisorption energies of adsorbates on alloy catalysts. The structure-energy descriptor is used to rationally design Pt-based and Ni-based alloy catalysts for NO oxidation. Full first principles calculations with kinetic simulations demonstrate that these designed catalysts possess much better catalytic performances than the traditional catalysts.

Efficient, Full Spectrum-Driven H2 Evolution Z-Scheme Co2P/CdS Photocatalysts with Co-S Bonds.

Exploring high-efficiency, low-cost, and stable photocatalysts that enable full solar spectrum including UV, visible, and near-infrared (NIR) light utilization for photocatalytic hydrogen generation still faces huge challenge. Herein, a Co2P/CdS Z-scheme photocatalyst without a noble metal is rationally fabricated to achieve ultrabroad UV-vis-NIR harvesting. Compared to Pt/CdS, CdS, and Co2P, the optimized Co2P/CdS exhibits much more outstanding performance with the H2 generation rates of 262.16, 66.98, and 3.93 mmol/g/h under solar, visible (780 nm > λ > 420 nm), and NIR (λ > 780 nm) light, respectively. Particularly, 10% Co2P/CdS displays a prominent apparent quantum efficiency value of 2.26% at 700 nm. The Z-scheme transform route can effectively enhance the separation of charge carriers in Co2P/CdS for UV-vis-driven HER, as confirmed by photoluminescence and photoelectrochemical measurements. More importantly, the Co-S bonds at the interface demonstrated by Fourier transform infrared, Raman (mapping), and X-ray photoelectron spectroscopy and density functional theory calculations can act as a "bridge" for charge transfer, thereby enhancing the full spectrum-driven H2 evolution. To the best of our knowledge, this is a rare research on full spectrum-driven photocatalytic HER without a noble metal.