Improved Plasmonic Hot‑Electron Capture in Au Nanoparticle/Polymeric Carbon Nitride by Pt Single Atoms for Broad‑Spectrum Photocatalytic H_(2)Evolution

ABSTRACT Rationally designing broad-spectrum photocatalysts to harvest whole visible-light region photons and enhance solar energy conversion is a“holy grail”for researchers,but is still a challenging issue.Herein,based on the common polymeric carbon nitride(PCN),a hybrid co-catalysts system comprising plasmonic Au nanoparticles(NPs)and atomically dispersed Pt single atoms(PtSAs)with different functions was constructed to address this challenge.For the dual co-catalysts decorated PCN(PtSAs–Au_(2.5)/PCN),the PCN is photoexcited to generate electrons under UV and short-wavelength visible light,and the synergetic Au NPs and PtSAs not only accelerate charge separation and transfer though Schottky junctions and metal-support bond but also act as the co-catalysts for H_(2) evolution.Furthermore,the Au NPs absorb long-wavelength visible light owing to its localized surface plasmon resonance,and the adjacent PtSAs trap the plasmonic hot-electrons for H_(2) evolution via direct electron transfer effect.Consequently,the PtSAs–Au_(2.5)/PCN exhibits excellent broad-spectrum photocatalytic H_(2) evolution activity with the H_(2) evolution rate of 8.8 mmol g^(−1) h^(−1) at 420 nm and 264μmol g^(−1) h^(−1) at 550 nm,much higher than that of Au_(2.5)/PCN and PtSAs–PCN,respectively.This work provides a new strategy to design broad-spectrum photocatalysts for energy conversion reaction.

CoxP@NiCo-LDH heteronanosheet arrays as efficient bifunctional electrocatalysts for co-generation of value-added formate and hydrogen with less-energy consumption

The inefficiency of water splitting is mainly due to the sluggish anodic water oxidation reaction. Replacing water oxidation with thermodynamically more favorable selective methanol oxidation reaction and developing robust bifunctional electrocatalysts are of great significance. Herein, a hierarchical heteronanostructure with Ni–Co layered double hydroxide(LDH) ultrathin nanosheets coated on cobalt phosphide nanosheets arrays(CoxP@NiCo-LDH) are fabricated and used for co-electrolysis of methanol/water to co-produce value-added formate and hydrogen with saving energy. Benefiting from the fast charge transfer introduced by phosphide nanoarrays, the synergy in nanosheets catalysts with hetero-interface,CoxP@NiCo-LDH/Ni foam(NF) exhibits superior electrocatalytic performance(10 mA cm-2@ 1.24 V and-0.10 V for methanol selective oxidation and hydrogen evolution reaction, respectively). Furthermore,CoxP@NiCo-LDH/NF-based symmetric two-electrode electrolyzer drives a current density of 10 m A cm-2 with a low cell voltage of only 1.43 V and the Faradaic efficiency towards the generation of formate and H2 are close to 100% in the tested range of current density(from 40 to 200 m A cm-2). This work highlights the positive effect of hetero-interaction in the design of more efficient eletrocatalysts and might guide the way towards facile upgrading of alcohols and energy-saving electrolytic H2 co-generation.

Photocatalytic H2 evolution improvement for H free-radical stabilization by electrostatic interaction of a Cu-BTC MOF with ZnO/GO

Metal-organic frameworks （MOFs） are self-assembled molecular containers that can encapsulate and stabilize short-lived reaction intermediates. In this study, the Cu-benzene-l,3,5-tricarboxylate （BTC） MOF was incorporated in a ZnO/graphene oxide （GO） photocatalytic system by electrostatic interaction, and the obtained assembly showed improved hydrogen evolution activity. Electron spin resonance analysis was used to detect and monitor free radicals in the photocatalytic system, and demonstrated that Cu-BTC MOF could stabilize and extend the lifetime of free radicals, increasing the chance of H. radical recombination to form H2. This work provides a new strategy for designing highly efficient photocatalysts.

Ternary titanium-oxo cluster/CdS/MIL-101 photocatalyst for H_2 evolution

Subject Code:B01 Photocatalytic hydrogen evolution by water-splitting has been recognized as one of the most promising solutions to the global energy and environment crisis,owing to its renewable solar energy source and clean chemical fuel product.Cadmium sulfide(CdS)and TiO2(or related polyoxo-titanium clusters)are two

Synthesis and Visible-light Photocatalytic Performance of C-doped Nb2O5 with High Surface Area

C-doped Nb2O5 with abundant mesopores has been successfully synthesized through a facile solvothermal synthetic strategy followed by calcination treatment. The resulting C-doped Nb2O5 displayed the highest BET surface area（345 m^2/g） and large mesopore size（ca. 4.2 nm）, capable of offering more accessible active sites as well as faster mass transfer for catalysis. Besides, the doping of C（2.21%, molar fraction） at the O sites in Nb2O5 lattice greatly enhanced visible-light response by lowering the band gap, thereby making the material a photocatalyst under visible-light irradiation. Typically, the C-doped Nb2O5 exhibited a high H2 evolution rate of ca. 39.10·μmol·g^-1·h^-1 and also degraded RhB dye completely after 30 min of visible light exposure, which turned out to be much better than Degussa P25 and pure Nb2O5 catalysts.

Cobalt-containing covalent organic frameworks for visible light-driven hydrogen evolution

Covalent organic frameworks(COFs) have recently emerged as a new class of photocatalysts.However,integrated design is crucial to maximizing the performance of COF-incorporating photocatalytic systems.Herein,we compare two strategies of installing earth-abundant metal-based catalytic centers into the matrice of a 2 D COF named NUS-55.Compared to NUS-55(Co)prepared from the post-synthetic metalation of coordination sites within the COF,the molecular co-catalyst impregnated NUS-55/[Co(bpy)3]Cl2 achieves a seven-fold improvement in visible light-driven H2 evolution rate to 2,480 μmol g^-1h^-1,with an apparent quantum efficiency(AQE) of 1.55% at 450 nm.Our results show that the rational design of molecular anchoring sites in COFs for the introduction of catalytic metal sites can be a viable strategy for the development of highly efficient photocatalysts with enhanced stability and photocatalytic activities.

2020 Roadmap on gas-involved photo-and electro-catalysis

Green reactions not only provide us chemical products without any pollution,but also offer us the viable technology to realize difficult tasks in normal conditions.Photo-,photoelectro-,and electrocatalytic reactions are indeed powerful tools to help us to embrace bright future.Especially,some gas-involved reactions are extremely useful to change our life environments from energy systems to liquid fuels and cost-effective products,such as H2 evolution(H2 production),02 evolution/reduction,CO2 reduction,N2 reduction(or N2 fixation) reactions.We can provide fuel cells clean H2 for electric vehicles from H2 evolution reaction(HER),at the same time,we also need highly efficient 02 reduction reaction(ORR) in fuel cells for improving the reaction kinetics.Moreover,we can get the clean oxidant O2 from water through O2 evolution reaction(OER),and carry out some reactions without posing any pollution to reaction systems.Furthermore,we can translate the greenhouse gas CO2 into useful liquid fuels through CO2 reduction reaction(CRR).Last but not the least,we can get ammonia from N2 reduction reaction(NRR),which can decrease energy input compared to the traditional Hubble process.These reactions,such as HER,ORR,OER,CRR and NRR could be realized through solar-,photoelectro-and electro-assisted ways.For them,the catalysts used play crucial roles in determining the efficiency and kinds of products,so we should consider the efficiency of catalysts.However,the cost,synthetic methods of catalysts should also be considered.Nowadays,significant progress has been achieved,however,many challenges still exist,reaction systems,catalysts underlying mechanisms,and so on.As extremely active fields,we should pay attention to them.Under the background,it has motivated us to contribute with a roadmap on ’GasInvolved Photo-and Electro-Catalysis’.

Osmotic-Enhanced-Photoelectrochemical Hydrogen Production Based on Nanofluidics

Harvesting clean energy such as solar energy and salinity gradient energy directly from the surrounding environment has attracted great attention.A promising proof-of-concept combination of cation-selective membrane-based osmotic energy with photoelectrochemical-based solar energy has been developed,highlighting the great potential for the direct conversion of osmotic energy to hydrogen energy.With the help of a 50-fold concentration gradient,the MXene-CdSe quantum dots system exhibits the highest photocurrent enhancement ratio(Δ/_(L-H)/Δ/_(L-L)),and the hydrogen production is increased by about 33%at a bias of 0 V versus reversible hydrogen electrode.Directly converting osmotic energy and solar energy into hydrogen energy suggests the possibility of coupling osmotic energy with other renewable energy sources.

Recent advances in rare-earth elements modification of inorganic semiconductorbased photocatalysts for efficient solar energy conversion: A review

This review focused on rare-earth elements containing inorganic semiconductor photocatalysts for efficient solar energy conversion. We also summarized the recent progress in the modification of the transition metal oxides and mixed oxides with rare earth ions. In the first section, we surveyed a variety of rare-earth elements modified TiO2 photocatalysts. Attributed to the modifica-tion with rare-earth elements, phase transformation of TiO2 from anatase to rutile was inhibited. Furthermore, the light-absorbing property of the TiO2 modified with rare-earth elements was also enhanced. In the second section, we summarized the effects of rare-earth elements on the modification of transition metal mixed oxides. It was believed that the corner-shared octahedral units in the form of networks, chains and slabs within the mixed oxide lattice were essential for the enhancement of the photocatalytic activity. In the last section, the strategy for the design of NIR or IR response upconversion composite photocatalysts was also discussed.

CdS-sensitized 3D ordered macroporous g-C_(3)N_(4)for enhanced visible-light photocatalytic hydrogen generation

Carbon nitride(g-C_(3)N_(4))is an attractive photocatalyst but commonly suffers from high photogenerated electron-hole recombination rate,low specific surface area,and narrow visible-light response range.Herein,3D ordered macroporous(3DOM)g-C_(3)N_(4)/CdS was constructed by a feasible and inexpensive synthesis strategy of using template and light-assisted methods to solve the above problems.The formed heterostructure with suitable morphology,band structure,and extended light absorption range is beneficial to promoting photocatalytic Hgeneration.3DOM g-C_(3)N_(4)/Cd S exhibits a high Hproduce rate of718.6μmol hg,which is 73.3 times higher than that of g-C_(3)N_(4)and 25.4 times higher than that of3DOM g-C_(3)N_(4).The 3DOM structure can effectively increase the path length of light of g-C_(3)N_(4),improve the light energy conversion efficiency,and shorten the carrier transport distance.CdS enhances visiblelight response and produces many surface sites.Constructing a stable and tight interface between 3DOM g-C_(3)N_(4)and Cd S can promote the migration of photogenerated electrons and holes and consequently the visible-light catalytic activity.This study offers an effective designing strategy for heterostructure photocatalysts to achieve high activity and stable solar H2production.

Synthesis of Holey Graphitic Carbon Nitride with Highly Enhanced Photocatalytic Reduction Activity via Melamine-cyanuric Acid Precursor Route

In this work,holey graphitic carbon nitride(HCN)was prepared by one-step thermal polymerization of hydrothermal product of melamine and then loaded with Ni/MoO2(NiMo)cocatalyst obtained by NaBHa reduction process.The obtained material was used for photocatalytic production of H2 from water reduction and H202 production from 02 reduction.The best photocatalyst(1%NiMo/HCN)exhibited a Hz evolution rate of 8.08 umolh while no H2 was detected over 1%NiMo-modifed bulk g-C3N4(BCN)under visible light illumination.Moreover,this rate is 1.7 times higher than that of 1%Pt-modified HCN.The 1%NiMo/HCN catalyst also exhibited the highest H20z production activity with a value of 6.13 umol/h.Such enhancement was ascribed to the efficient charge carrier separation and migration,which were promoted by the large specific surface area and pore volume of HCN and the synergy between MoO2 and Ni.The proposed method to obtain HCN is expected to open up new ways in development of highly-active HCN-based photocatalysts for photocatalytic reduction reactions.

Accumulation of localized charge on the surface of polymeric carbon nitride boosts the photocatalytic activity

The random mobility of charge carriers is a main factor causing the low photocatalytic efficiency of gCN.Thus,the controllable migration of charge carriers is a rational strategy to suppress the charge recombination and facilitate charge separation.Herein,an ethylenediamine modified g-C_(3)N_(4)displays improved photocatalytic activity.The excellent charge separation efficiency is confirmed to be a key factor for the enhancement.The TEM observation after photo-depositing Pt nanoparticles and DFT calculations verify the accumulation of electrons on some areas of g-C_(3)N_(4)surface.The increased-NH_(2)groups significantly tune the electronic structure of g-C_(3)N_(4)after the modification.The generation of midgap states also affects the charge separation.Our reports provide a simple method to manage the migration of charge carriers and enable electrons directional transfer,which suppresses the recombination and improves the photocatalytic activity.