Structural analysis of transient reaction intermediate in formic acid dehydrogenation catalysis using two-dimensional IR spectroscopy.

The molecular structure of a catalytically active key intermediate is determined in solution by employing 2D IR spectroscopy measuring vibrational cross-angles. The formate intermediate (2) in the formic acid dehydrogenation reaction catalyzed by a phosphorus-nitrogen PN3P-Ru catalyst is elucidated. Our spectroscopic studies show that the complex features a formate ion directly attached to the Ru center as a ligand, and a proton added to the imine arm of the dearomatized PN3P* ligand. During the catalytic process, the imine arms are not only reversibly protonated and deprotonated, but also interacting with the protic substrate molecules, effectively serving as the local proton buffer to offer remarkable stability with a turnover number (TON) over one million.

High-performance Förster resonance energy transfer-based dye-sensitized photocatalytic H2 evolution with graphene quantum dots as the homogeneous energy donor.

A high-performance dye-sensitized photocatalytic H2 evolution system was developed based on Förster resonance energy transfer (FRET) by employing water-soluble and highly photoluminescent N,S codoped graphene quantum dots (NSGQDs) as the homogeneous energy donor, erythrosin B (ErB) as the sensentizing dye, and platinum nanoparticles (Pt NPs) as the catalyst. NSGQDs absorbed high-energy photons that undergo FRET to transfer the excitation energy to the sensitizing ErB for maximizing light absorption and also served as an electron transfer and loading matrix of Pt NPs for accelarating the electron transfer; as a result, the ErB-sensitized NSGQD-Pt system afforded much higher H2 evolution activity than the NSGQD-free dye-sensitized system.

Dehydrogenation of Formic Acid Catalyzed by a Ruthenium Complex with an N,N'-Diimine Ligand.

We report a ruthenium complex containing an N,N'-diimine ligand for the selective decomposition of formic acid to H2 and CO2 in water in the absence of any organic additives. A turnover frequency of 12 000 h-1 and a turnover number of 350 000 at 90 °C were achieved in the HCOOH/HCOONa aqueous solution. Efficient production of high-pressure H2 and CO2 (24.0 MPa (3480 psi)) was achieved through the decomposition of formic acid with no formation of CO. Mechanistic studies by NMR and DFT calculations indicate that there may be two competitive pathways for the key hydride transfer rate-determining step in the catalytic process.

Efficient Electrocatalytic Reduction of CO2 by Nitrogen-Doped Nanoporous Carbon/Carbon Nanotube Membranes: A Step Towards the Electrochemical CO2 Refinery.

Herein we introduce a straightforward, low cost, scalable, and technologically relevant method to manufacture an all-carbon, electroactive, nitrogen-doped nanoporous-carbon/carbon-nanotube composite membrane, dubbed "HNCM/CNT". The membrane is demonstrated to function as a binder-free, high-performance gas diffusion electrode for the electrocatalytic reduction of CO2 to formate. The Faradaic efficiency (FE) for the production of formate is 81 %. Furthermore, the robust structural and electrochemical properties of the membrane endow it with excellent long-term stability.

High-Sulfur-Vacancy Amorphous Molybdenum Sulfide as a High Current Electrocatalyst in Hydrogen Evolution.

The remote hydrogen plasma is able to create abundant S-vacancies on amorphous molybdenum sulfide (a-MoSx ) as active sites for hydrogen evolution. The results demonstrate that the plasma-treated a-MoSx exhibits superior performance and higher stability than Pt in a proton exchange membrane based electrolyzers measurement as a proof-of-concept of industrial application.

Water-soluble fullerenol-mediated electron transfer in molecular systems toward enhanced solar hydrogen production.

We present here that visible-light-induced electron transfer from an excited dye to an in situ generated Pt cocatalyst can be promoted by employing water-soluble fullerenol (C60(OH)24) as an electron mediator, and as a result, the fullerenol-based molecular system shows a 3 times higher H2 evolution activity than C60(OH)24-free system.

A hierarchical carbon foam-hosted Co2P nanoparticles monolithic electrode for ampere-level and super-durable electrocatalytic hydrogen production.

In this work, we develop a hierarchical carbon foam-based monolithic electrode (Co2P@HCF) from Co2+-adsorbed polyvinyl alcohol (PVA) sponge via the successive carbonization and phosphorization. Owing to the 3D hierarchical porous structure, excellent electrolyte wettability, good mechanical strength, and intimate embedding of highly dispersed Co2P nanoparticles, the Co2P@HCF electrode delivers a high current density of 1.0 A cm-2 for the hydrogen evolution reaction (HER) at ultralow overpotentials of 189.6 and 218.6 mV in 0.5 M H2SO4 and 1.0 M KOH solutions, respectively, with remarkable durability for 100 h.

An in situ exsolved Cu-based electrocatalyst from an intermetallic Cu5Si compound for efficient CH4 electrosynthesis.

A Cu-based electrocatalyst (e-Cu5Si) is developed by in situ exsolving ultrathin SiOx layer-coated CuO/Cu nanoparticles (<100 nm) on the surface of a conductive intermetallic Cu5Si parent. This specially designed e-Cu5Si catalyst exhibits high performance for the CO2 reduction reaction (CO2RR), which affords an excellent CH4 faradaic efficiency (FE) of 49.0% with partial current density of over 140.1 mA cm-2 at -1.2 V versus reversible hydrogen electrode (RHE) in a flow cell, with outstanding stability. The strongly coupled multiphase interfaces among the SiOx layer, CuO/Cu species, and substrate contribute to fast interfacial electron transfer for the CO2RR. Moreover, in situ Raman analysis suggests that the ultrathin SiOx layer simultaneously stabilizes the active Cu1+ species and promotes the protonation of *CO to form *CHxO, thereby greatly improving overall selectivity and activity of CH4 production.

A Cu hollow fiber with coaxially grown Bi nanosheet arrays as an integrated gas-penetrable electrode enables high current density and durable formate electrosynthesis.

While high current density formate (HCOO-) electrosynthesis from CO2 reduction has been achieved in a flow cell assembly, the inevitable flooding and salt precipitation of traditional gas-diffusion electrodes (GDEs) severely limit the overall energy efficiency and stability. In this work, an integrated gas-penetrable electrode (GPE) for HCOO- electrosynthesis was developed by coaxially growing vertically aligned high density Bi nanosheet arrays on a porous Cu hollow fiber (Bi NSAs@Cu HF) via controllable galvanic replacement. The interior porous Cu HF serves as a robust gas-penetrable and conductive host for continuously delivering CO2 gas to surface-anchored Bi NSAs, resulting in numerous well-balanced triphase active interfaces for the electrocatalytic CO2 reduction reaction (CO2RR). The most active Bi NSAs@Cu HF GPE exhibits a high HCOO- faradaic efficiency (FEHCOO-) of over 80% in a wide potential window (330 mV) with a linearly increased partial current density (jHCOO-) up to -261.6 mA cm-2 at -1.11 V vs. the reversible hydrogen electrode (RHE). The Bi NSAs@Cu HF GPE also sustains a FEHCOO- of >80% at a high total current density of -300 mA cm-2, corresponding to a jHCOO- of >-240 mA cm-2, for more than 60 h. This work provides new perspectives on designing efficient and durable integrated GPEs for a sustainable CO2RR on a large scale.

Efficient electrocoupling of CO2 and N2 to urea by a gas-penetrable Bi nanosheet-wrapped Cu hollow fiber.

A gas-penetrable electrode (GPE) composed of a Bi nanosheet array-wrapped Cu hollow fiber (Bi NSAs@Cu HF) is rationally designed and utilized for efficient electrocoupling of CO2 and N2 to produce urea with a yield of 79 µg h-1 cm-2, a faradaic efficiency (FEurea) of 6.8%, and excellent cycling stability at -0.2 V vs. reversible hydrogen electrode (RHE).

ZnO-templated hollow amorphous carbon: oxygen adsorption and doping synergy for enhanced ORR catalysis.

In pursuit of highly active zinc-air battery (ZAB) catalysts, nitrogen doping has proven key to enhancing carbon-based non-metallic catalysts' performance in the oxygen reduction reaction (ORR). This study employed a novel method to synthesize variously sized ZnO materials coated with ZIF-8. Notably, smaller particle sizes correlated with reduced activation energy. ZnO-12, the smallest variant, fully carbonized at 800 °C, resulting in zinc ion evaporation and the formation of an amorphous carbon nano-hollow structure, ZIF8/ZnO-12. This material showcased remarkable ORR properties, with an onset potential of 0.9 V (vs. RHE) and a Tafel slope of 71.4 mV dec-1, surpassing the benchmark Pt/C catalyst and exhibiting excellent stability. Moreover, in ZAB tests, ZIF8/ZnO-12 achieved a specific capacity of 816 mA h g-1, outperforming Pt/C. DFT calculations indicate that under alkaline conditions, nitrogen-doped carbon materials containing adsorbed oxygen and doped oxygen exhibit lower catalytic activation energy for the ORR, which is beneficial for accelerating the ORR. This research provides valuable insights into designing more efficient carbon-based non-metallic catalysts for ZABs.

Lignin as a quasi-homogenous electron mediator enables efficient photocatalytic H2 evolution in molecular systems.

We report that the biomass-derived lignosulfonate (LS) can function as a quasi-homogenous electron mediator to efficiently promote the electron transfer from the excited erythrosin B (ErB) to the in situ generated Pt cocatalyst under visible light, thus enhancing the photocatalytic H2 evolution activity by over 10 fold as compared to the LS-free system.

Boosting CO2 electroreduction on a Zn electrode via concurrent surface reconstruction and interfacial surfactant modification.

Herein, we report an effective strategy for improving the electrocatalytic CO2 reduction reaction (CO2RR) performance of a Zn foil electrode via concurrent surface reconstruction and interfacial surfactant modification. The oxide-derived and CTAB-modified Zn electrode (OD-Zn-CTAB) prepared by electrochemically reducing the air-annealed Zn foil electrode in the presence of CTAB exhibits high electrocatalytic activity and selectivity for CO production with a CO partial current density (jCO) of 8.2 mA cm-2 and a CO faradaic efficiency (FECO) of 90% at -1.0 V vs. the reversible hydrogen electrode (RHE), greatly outperforming the pristine Zn foil (FECO = 32.0%; jCO = 0.5 mA cm-2) and OD-Zn (FECO = 77.6%; jCO = 5.0 mA cm-2) obtained by electroreduction of annealed Zn. The greatly enhanced CO2RR performance of OD-Zn-CTAB can be attributed to the increased number of active sites originating from the surface reconstruction and the formation of a favorable CTAB-modified electrode/electrolyte (E/E) interface that can efficiently adsorb and activate CO2 while inhibiting the competitive H2 evolution reaction.

In situ self-exsolved ultrasmall Fe2P quantum dots from attapulgite nanofibers as superior cocatalysts for solar hydrogen evolution.

Developing highly active, stable, and cost-efficient cocatalysts for photocatalytic H2 evolution is pivotal in the area of renewable energy conversion. Herein, we present a straightforward, low-temperature phosphidation strategy for in situ exsolving doped Fe ions from natural attapulgite (ATP) nanofibers into a supported Fe2P cocatalyst for the photocatalytic H2 evolution reaction (HER). The resulting Fe2P QDs/ATP features highly dispersed Fe2P QDs with an average size of <2 nm and a strong interfacial interaction between self-exsolved Fe2P QDs and the ATP substrate, thus providing ample and stable active sites for the photocatalytic HER. When employed as a cocatalyst, Fe2P QDs/ATP exhibits superior catalytic activity and notable stability in a molecular system with low-cost xanthene dyes as the photosensitizer under visible light irradiation. More importantly, Fe2P QDs/ATP can also efficiently and stably catalyze the photocatalytic HER when simply combined with various semiconductor photocatalysts (g-C3N4, TiO2, and CdS). This strategy of exsolving transition metal ions from substrates is an effective yet simple approach for the development of highly active supported HER cocatalysts for renewable and clean energy conversion.

Ni2P nanowire arrays grown on Ni foam as an efficient monolithic cocatalyst for visible light dye-sensitized H2 evolution.

Nanostructured H2 evolution cocatalysts are able to promote charge separation and thus enhance the efficiency of the photocatalytic H2 evolution reaction (HER). However, the nanosized cocatalyst particles are easily detached from the surfaces of semiconductors or severely aggregated in reaction systems, which not only greatly reduces the photocatalytic HER efficiency during long-term use but also greatly increases the difficulty of recovery. Moreover, powdery cocatalysts have poor compatibility with the scale-up photoelectrochemical devices. In this paper, a monolithic cocatalyst is developed by controllably growing Ni2P nanowire arrays on Ni foam substrate (Ni2P NWAs/NF) via a direct vapor-phase phosphorization method. The grown Ni2P NWAs with high specific surface areas can not only offer ample active sites for the HER, but also serve as scaffolds for anchoring dye molecules to maximize the light utilization efficiency, which endows the Ni2P NWAs/NF monolithic cocatalyst with excellent HER activity. When sensitized with Erythrosin B (ErB) in triethanolamine (TEOA) solution, the turnover number (TON) of H2 evolution based on ErB reaches 9.7 in 5 h under visible light. Notably, the good structural integrity and inherent magnetism enable the Ni2P NWAs/NF to be easily separated from the reaction solution and excellent catalytic H2 evolution stability over a 45 h cycling reaction. This work presents a new strategy of fabricating monolithic cocatalysts with controllable microstructure and functionalities as well as high activity, durability, and device-compatibility for large-scale solar energy conversion applications.

Ni single atoms supported on hierarchically porous carbonized wood with highly active Ni-N4 sites as a self-supported electrode for superior CO2 electroreduction.

Powdery N-doped carbon-supported single-atom catalysts (SACs) can be prepared on a large scale and are highly selective in converting CO2 to CO, but their practical application is restricted by their powdery texture. Herein, we report Ni single atoms supported on hierarchically porous N-doped carbonized wood (Ni SAs-NCW) as a self-supported electrode for efficient and durable CO2 electroreduction. The porous NCW matrix possesses an abundance of open aligned microchannels that allow unimpeded CO2 diffusion and electrolyte transportation while the uniformly dispersed Ni SAs in the NCW matrix in the Ni-N4 configuration afford ample highly active sites for CO2 electroreduction. This Ni SAs-NCW electrode exhibits a high CO2-to-CO faradaic efficiency (FECO) of 92.1% and a CO partial current density (jCO) of 11.4 mA cm-2 at -0.46 V versus the reversible hydrogen electrode (RHE) and maintains a stable FECO and jCO over a period of 9 h of electrolysis. This work provides an effective strategy to develop efficient SACs with potential to be integrated into flow cell systems for large-scale CO2 reduction.

Carbonized wood membrane decorated with AuPd alloy nanoparticles as an efficient self-supported electrode for electrocatalytic CO2 reduction.

Efficient electrocatalytic reduction of CO2 to value-added chemicals and fuels is a promising technology for mitigating energy shortage and pollution issues yet highly relay on the development of high-performance electrocatalysts. Herein, we develop an effective strategy to fabricate carbonized wood membrane (CW) decorated with AuPd alloy nanoparticles with tunable composition (termed as AuPd@CW) as self-supported electrodes for efficient electrocatalytic CO2 reduction. The uniformly distributed AuPd nanoparticles on wood matrix are first achieved through the in-situ reduction of metal cations by the lignin content in wood. Subsequently, two-step carbonization was employed to promote the alloying of AuPd nanoparticles and the formation of CW. The AuPd@CW membrane electrode features an integrated macroscopic structure with numerous open and aligned channels for rapid electron transfer and mass diffusion and well-dispersed AuPd alloy nanoparticles as active sites for the CO2 reduction. The optimal Au95Pd5@CW electrode affords a high selectivity for CO2 electroreduction with a maximum CO faradaic efficiency (FECO) of 82% at an overpotential of 0.49 V, much higher than those obtained on Au@CW and Pd@CW electrodes. The CO current density and FECO remain relatively stable during a 12 h electrolysis reaction. In addition, density functional theory (DFT) calculations reveal that alloying Au with Pd enables a balance between the formation of intermediate COOH* and the desorption of CO on the surface of AuPd nanoparticles, thus enhancing the selectivity of CO production. This work offers an effective strategy for the fabrication of bimetallic alloys supported on wood-based carbon membrane as a practical electrode for electrochemical energy conversion.

MAPbI3 microcrystals integrated with Ti3C2Tx MXene nanosheets for efficient visible-light photocatalytic H2 evolution.

Integrating Ti3C2Tx MXene nanosheets (Ti3C2Tx NSs) as an efficient cocatalyst with MAPbI3 microcrystals results in superior MAPbI3-Ti3C2Tx NS composite photocatalysts for H2 evolution from MAPbI3-saturated HI aqueous solution using visible light. The best MAPbI3 (100 mg)-Ti3C2Tx NS (10 mg) composite exhibits a H2 evolution rate of 63.6 µmol h-1, which is 43 times higher than that of pristine MAPbI3, and a stable H2 evolution activity over a 120 h repeating reaction.

Conductive polyaniline-mediated efficient electron transfer in Z-scheme photocatalysts for enhanced overall water splitting.

Here, we demonstrate that conductive polyaniline (PANI) can function as a solid redox mediator to efficiently shuttle photogenerated electrons from BiVO4 to Ru/SrTiO3:Rh, thus greatly promoting the separation of electrons and holes and nearly quadrupling the overall water splitting activity under visible light irradiation (λ ≥ 420 nm).

An all-inorganic quasi-homogenous polyoxometalate/[Mo3S13]2- system for efficient and stable photocatalytic H2 evolution.

An all-inorganic quasi-homogenous photocatalytic H2 evolution system has been developed employing Keggin-type polyoxometalate H4SiW12O40 (SiW12) as the photosensitizer and [Mo3S13]2- clusters as the catalyst. This SiW12/[Mo3S13]2- system achieves a high turnover number (TON) of 922 based on the [Mo3S13]2- catalyst in 5 h of reaction and excellent H2 evolution stability for 40 h with a high turnover number of 6876.