The incorporation of cocatalyst cobalt sulfide into graphitic carbon nitride:Boosted photocatalytic hydrogen evolution performance and mechanism exploration

2D-layered graphitic carbon nitride(g-C_(3)N_(4))is regarded as a great prospect as a photocatalyst for H_(2)generation.However,g-C_(3)N_(4)’s photocatalytic hydrogen evolution(HER)activity is significantly restricted by the recombination of photocarriers.We find that cobalt sulfide(CoS_(2))as a cocatalyst can promote g-C_(3)N_(4)nanosheets(NSs)to realize very efficient photocatalytic H_(2)generation.The prepared CoS_(2)/g-C_(3)N_(4)hybrids display highly boosted photocatalytic H_(2)generation performance and outstanding cycle stability.The optimized 7%-CoS_(2)/g-C_(3)N_(4)hybrids show a much improved photocatalytic H_(2)generation rate of 36.2μmol-1h-1,which is about 180 times as much as bare g-C_(3)N_(4)(0.2μmol-1h-1).In addition,the apparent quantum efficiency(AQE)of all the samples was computed under light atλ=370 nm,in which the AQE of 7%-CoS_(2)/g-C_(3)N_(4)hybrids is up to 5.72%.The experimental data and the DFT calculation suggest that the CoS_(2)/g-C_(3)N_(4)hybrid’s excellent HER activity is attributable to the lower overpotential and the smaller Co-H bond activation energy for HER.Accordingly,the CoS_(2)cocatalyst loading effectively boosts the photocatalytic performance of g-C_(3)N_(4)for H_(2)evolution.The project promotes fast development of high-efficiency photocatalysts and low-cost for photocatalytic H_(2)generation.

General approach for atomically dispersed precious metal catalysts toward hydrogen reaction

As a carbon-free energy carrier,hydrogen has become the pivot for future clean energy,while efficient hydrogen production and combustion still require precious metal-based catalysts.Single-atom catalysts(SACs)with high atomic utilization open up a desirable perspective for the scale applications of precious metals,but the general and facile preparation of various precious metal-based SACs remains challenging.Herein,a general movable printing method has been developed to synthesize various precious metal-based SACs,such as Pd,Pt,Rh,Ir,and Ru,and the features of highly dispersed single atoms with nitrogen coordination have been identified by comprehensive characterizations.More importantly,the synthesized Pt-and Ru-based SACs exhibit much higher activities than their corresponding nanoparticle counterparts for hydrogen oxidation reaction and hydrogen evolution reaction(HER).In addition,the Pd-based SAC delivers an excellent activity for photocatalytic hydrogen evolution.Especially for the superior mass activity of Ru-based SACs toward HER,density functional theory calculations confirmed that the adsorption of the hydrogen atom has a significant effect on the spin state and electronic structure of the catalysts.

Experimental and theoretical investigation of sulfur-doped g-C_(3)N_(4)nanosheets/FeCo_(2)O_(4)nanorods S-scheme heterojunction for photocatalytic H_(2)evolution

g-C_(3)N_(4)emerges as a promising metal-free semiconductor photocatalyst due to its cost-effectiveness,facile synthesis,suitable visible light response,and robust thermal stability.However,its practical application in photocatalytic hydrogen evolution reaction(HER)is impeded by rapid carrier recombination and limited light absorption capacity.In this study,we successfully develop a novel g-C_(3)N_(4)-based step-scheme(S-scheme)heterojunction comprising two-dimensional(2D)sulfur-doped g-C_(3)N_(4)nanosheets(SCN)and one-dimensional(1D)FeCo_(2)O_(4)nanorods(FeCo_(2)O_(4)),demonstrating enhanced photocatalytic HER activity.The engineered SCN/FeCo_(2)O_(4)S-scheme heterojunction features a well-defined 2D/1D heterogeneous interface facilitating directed interfacial electron transfer from FeCo_(2)O_(4)to SCN,driven by the lower Fermi level of SCN compared to FeCo_(2)O_(4).This establishment of electron-interacting 2D/1D S-scheme heterojunction not only facilitates the separation and migration of photogenerated carriers,but also enhances visible-light absorption and mitigates electron-hole pair recombination.Band structure analysis and density functional theory calculations corroborate that the carrier migration in the SCN/FeCo_(2)O_(4)photocatalyst adheres to a typical S-scheme heterojunction mechanism,effectively retaining highly reactive photogenerated electrons.Consequently,the optimized SCN/FeCo_(2)O_(4)heterojunction exhibits a substantially high hydrogen production rate of 6303.5μmol·g^(-1)·h^(-1)under visible light excitation,which is 2.4 times higher than that of the SCN.Furthermore,the conjecture of the S-scheme mechanism is confirmed by in situ XPS measurement.The 2D/1D S-scheme heterojunction established in this study provides valuable insights into the development of high-efficiency carbon-based catalysts for diverse energy conversion and storage applications.

Aromatic alcohols oxidation and hydrogen evolution over π-electron conjugated porous carbon nitride rods

Photocatalysis using polymeric carbon nitride(CN)materials is a constantly evolving field,where the variation of synthetic procedures allows the constant improvement of activity by tackling the intrinsic limitations of these materials(optical absorbance,specific surface area,charge migration,etc.).Amongst the possible photocatalytic reactions,the most popular application of CNs is the hydrogen evolution reaction(HER)from water.In this work,we design precisely-controlled carbon-doped porous CN rods with extended π-electron conjugation from supramolecular assemblies of melem and co-monomers,which partially substitute nitrogen for carbon atoms at the pyrimidine ring of the melem.Dense hydrogen bonds and good thermal stability of the melem-based supramolecular framework allow synthesizing a more ordered structure for improved charge migration;the control from the molecular level over the position of carbon-substituted nitrogen positions tailors the band alignment and photogenerated charge separation.The optimal photocatalyst shows an excellent HER rate(up to 10.16 mmol·h-1·g-1 under 100 W white light-emitting diode(LED)irradiation,with an apparent quantum efficiency of 20.0%at 405 nm,which is 23.2 times higher compared to a reference bulk CN).To fully harness the benefits of the developed metal-free CNs,selective oxidation reaction of aromatic alcohols is demonstrated with high conversion and selectivity.