A cascade of in situ conversion of bicarbonate to CO_(2) and CO_(2) electroreduction in a flow cell with a Ni-N-S catalyst

Combination of CO_(2) capture using inorganic alkali with subsequently electrochemical conversion of the resultant HCO_(3)^(-)to high-value chemicals is a promising route of low cost and high efficiency.The electrochemical reduction of HCO_(3)^(-)is challenging due to the inaccessible of negatively charged molecular groups to the electrode surface.Herein,we adopt a comprehensive strategy to tackle this challenge,i.e.,cascade of in situ chemical conversion of HCO_(3)^(-)to CO_(2) and CO_(2) electrochemical reduction in a flow cell.With a tailored Ni-N-S single atom catalyst(SACs),where sulfur(S)atoms located in the second shell of Ni center,the CO_(2)electroreduction(CO_(2)ER)to CO is boosted.The experimental results and density functional theory(DFT)calculations reveal that the introduction of S increases the p electron density of N atoms near Ni atom,thereby stabilizing^(*)H over N and boosting the first proton coupled electron transfer process of CO_(2)ER,i.e.,^(*)+e^(-)+^(*)H+^(*)CO_(2)→^(*)COOH.As a result,the obtained catalyst exhibits a high faradaic efficiency(FE_(CO)~98%)and a low overpotential of 425 mV for CO production as well as a superior turnover frequency(TOF)of 47397 h^(-1),outcompeting most of the reported Ni SACs.More importantly,an extremely high FECOof 90%is achieved at 50 mA cm^(-2)in the designed membrane electrode assembly(MEA)cascade electrolyzer fed with liquid bicarbonate.This work not only highlights the significant role of the second coordination on the first coordination shell of the central metal for CO_(2)ER,but also provides an alternative and feasible strategy to realize the electrochemical conversion of HCO_(3)^(-)to high-value chemicals.

In-situ doping-induced lattice strain of NiCoP/S nanocrystals for robust wide pH hydrogen evolution electrocatalysis and supercapacitor

Developing high-efficiency multifunctional nanomaterials is promising for wide p H hydrogen evolution reaction(HER) and energy storage but still challenging. Herein, a novel in-situ doping-induced lattice strain strategy of NiCoP/S nanocrystals(NCs) was proposed through using seed crystal conversion approach with NiCo_(2)S_(4) spinel as precursor. The small amount of S atoms in NiCoP/S NCs perturbed the local electronic structure, leading to the atomic position shift of the nearest neighbor in the protocell and the nanoscale lattice strain, which optimized the H* adsorption free energy and activated H_(2)O molecules, resulting the dramatically elevated HER performance within a wide p H range. Especially, the NiCoP/S NCs displayed better HER electrocatalytic activity than comical 20% Pt/C at high current density in 1 M KOH and natural seawater: it only needed 266 m V vs. reversible hydrogen electrode(RHE) and660 m V vs. RHE to arrive the current density of 350 m A cm^(-2) in 1 M KOH and natural seawater, indicating the application prospect for industrial high current. Besides, NiCoP/S NCs also displayed excellent supercapacitor performance: it showed high specific capacity of 2229.9 F g^(-1) at 1 A g^(-1) and energy density of87.49 Wh kg^(-1), when assembled into an all-solid-state flexible device, exceeding performance of most transition metal phosphides. This work provides new insights into the regulation in electronic structure and lattice strain for electrocatalytic and energy storage applications.

Ultra-small Co/CoO_(x) nanoparticles dispersed on N-doped carbon nanosheets for highly efficient electrocatalytic oxygen evolution reaction

In this paper,we report a facile strategy to synthesize Co-BDC-NH2 material,which is used as a precursor towards an excellent OER electrocatalyst by thermal annealing in nitrogen.Ultra-small Co/Co Oxnanoparticles were uniformly dispersed on the rhombus N-doped carbon(NC)nanoflakes.Transmission electron microscopic,X-ray diffraction spectrometric,and X-ray photoelectron spectroscopic analyses revealed the coexistence of metallic Co and Co oxides nanoparticles.It was found that Co/CoO_(x)@NC obtained at 500℃ annealing temperature exhibited the highest electrocatalytic OER activity,with 307 and375 m V overpotential to achieve 10 and 100 m A cm^(-2) current densities.Besides,thanks to the in-situ annealing process,Co/CoO_(x)@NC showed excellent catalytic stability with 97.4%current density retention after 24 h electrolysis at 1.66 V vs.RHE electrode potential.Further investigations revealed that the ultrasmall Co/Co Oxnanoparticles distributed on N-doped carbon template contribute significantly towards OER electrocatalysis through enlarging the activity surface areas and enhancing the intrinsic electrochemical activity due to the presence of metallic Co.

Hierarchical Cu_(3)P-based nanoarrays on nickel foam as efficient electrocatalysts for overall water splitting

Exploring the efficient bifunctional catalysts and binder-free electrode materials for both oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)is receiving continuous interest.Herein,we report the fabrication of hierarchical copper phosphide nanoarrays(Cu_(3)P)on three-dimensional(3D)nickel foam(NF)through a template-directed synthetic strategy as electrocatalysts for overall water splitting.Specifically,the Cu_(3)P/NF electrode demonstrates a remarkably low overpotential of~331 m V to approach the current density of 50 m A cm^(-2)in the OER,and an overpotential of~115 m V to achieve-10 m A cm^(-2)current density in the HER.Meanwhile the Cu_(3)P/NF catalyst could hold a great stability for both reactions in alkaline condition,reflected in 37 h for OER and 24 h for HER of consistent galvanostatic electrolysis.As revealed by TEM,STEM and XPS characterizations,the high catalytic OER activity can be ascribed to the 3D open structure of Cu_(3)P/NF and the abundant Cu O active sites in hierarchical Cu O/Cu_(3)P/NF structure after in-situ activation.Furthermore,the overall water splitting is conducted in a two-electrode cell,which requires only a cell voltage of 1.63 V to approach 10 m A cm^(-2)with a good stability of 20 h.This protocol of Cu_(3)P/NF electrode affords a general strategy to construct hierarchically structured metal phosphides for clean energy-related application.

Engineering the efficient three-dimension hollow cubic carbon from vacuum residuum with enhanced mass transfer ability towards H2O2 production

Constructing efficient carbon material with enhanced mass transfer ability from vacuum residuum(VR)is of prime industrial and scientific significance.Herein,we demonstrated a one-pot synthesis of metal-free and highly symmetric hollow carbon cubes(HCCs)using cost-efficient vacuum residuum(VR)as a C/N/S source.By multi-techniques such as TEM,SEM,Raman,XPS,and XRD,it is found that the CTAB surfactant plays an important role in emulsifying and forming oil-in-water suspension particles.Subsequently,high aromatics contents in VR favor the formation of HCCs shell by graphitization on the surface of Na Cl template.Notably,heavy metals(e.g.,V,Ni)are not enriched in carbon skeleton due to the unique graphitization mechanism.This metal-free HCCs catalyst showed good catalytic stability and high selectivity towards direct and local electrochemical production of hydrogen peroxide(H_(2)O_(2))through two-electron O_(2)reduction due to enhanced mass transfer ability.The results provide a novel avenue to synthesize metal-free cubic carbon material from low-cost and plentiful VR,which are essential to the design of more efficient catalysts for O_(2)reduction to H_(2)O_(2).

Efficiently coupled glucose oxidation for high-value D-glucaric acid with ultradurable hydrogen via Mn(III)in acidic solution

The electrooxidation of the alcohol and aldehyde molecules instead of water coupled with H2 production has been proven to be effective for producing high-value fine chemicals under alkaline conditions.It is also noteworthy that under acidic conditions,the stability of non-noble metal water oxidation catalysts remains a great challenge due to the lattice oxygen mechanism.Hence,we coupled the biomass-derived glucose oxidation for high-value D-glucaric acid(GRA)with ultra-durable hydrogen in acid solution over a Yb-MnO_(2)catalyst.The Mn^(3+)regulated by Yb atoms doped in MnO_(2)can effectively optimize the adsorption and desorption processes of the alcohol and aldehyde group and improve the intrinsic activity but cannot for H2O.The catalyst exhibited extremely high activity and stability after 50 h for glucose oxidation,inhibiting the lattice oxygen process and MnO4−formation,while the activity was quickly lost within 0.5 h for water oxidation.Density functional theory(DFT)calculations further demonstrated that glucose oxidation reaction proceeds preferentially due to the oxidation of aldehyde group with lower adsorption-free energy(−0.4 eV)than water(ΔG>0 eV),avoiding the lattice oxygen mechanism.This work suggests that biomass-derived glucose oxidation not only provides a cost-effective approach for high-value chemicals,but also shows an extremely potential as an alternative to acidic oxygen evolution reaction(OER)for ultradurable H2 production.

Free radicals induced ultra-rapid synthesis of N-doped carbon sphere catalyst with boosted pyrrolic N active sites for efficient acetylene hydrochlorination

Activated carbon-supported HgCl2 catalysts have seriously impeded the development of the polyvinyl chloride(PVC)industry due to the sublimation of Hg species and environmental pollution problems.Herein,the template-free and organic solvent-free strategy was devised to synthesize non-metallic based nitrogen-doped carbon(U-NC)sphere catalyst for acetylene hydrochlorination.This green strategy via ultrasonic chemistry initiates resin crosslinking reactions between aminophenol and formaldehyde resin by free radicals,leading to the ultra-rapid formation of U-NC with remarkably high pyrrolic N content in only 5 min.This U-NC catalyst exhibited an outstanding space-time-yield(1.6 gVCM·gcat^(−1)·h^(−1)),even comparable to the reported metallic catalyst.By combining kinetic analysis,advanced characterizations,density functional theory,it is found that the amount of pyrrolic N is in linear with C_(2)H_(2)conversion,pyrrolic N in U-NC can effectively improve acetylene hydrochlorination performance by mediating HCl adsorption.This work sheds new light on rationally constructing metal-free catalyst for acetylene hydrochlorination.