Research On Electrode Performance Of Photo-electrochemical Water Oxidation And Selective Reduction For 5-hydroxymethyl Furfural

In photoelectrochemical reactions,clean energy hydrogen and hydrogen peroxide can be obtained by water decomposition.The oxidation of water is a key step.In this paper,using the resonance effect of Au @SiO₂ to increase the light absorption of the BiVO₄ electrode and the separation of photo-induced charge,thus improving the performance of BiVO₄ water oxidation.Reducing biomass 5-hydroxymethylfurfural?HMF?can produce high value-added chemicals,2,5-dihydroxymethyl furan?DHMF?,which has important application value.?Noble?metal electrodes is often used to reduce HMF,however producing many kinds of products.It is challenging to design high performance catalytic electrode and control target product selectivity.Cu₂O was first applied to reduce HMF and investgate the effect on selectivity of the target product DHMF by adjusting crystal face of the Cu₂O film.1.Au@SiO₂/BiVO₄ was prepared by simply droping the core-shell Au@SiO₂ nanoparticles to the surface of BiVO₄.The current density of the photoanode was 1.15 mA·cm^-2?1.23V vs.RHE?,increased by about 2.5 times in PBS compared with the pristine BiVO₄ and the oxidation efficiency increased by about 2.6 times.Because the resonance effect enhanced the electric field at Au@SiO₂ and electrode interface,accelerating transformation of photogenerated charge.While the current density of contrast electrode Au/BiVO₄ was not improved.The reason was Au nanoparticals were gathered on BiVO₄ surface,SiO₂ shell can protect Au nanoparticals and the size of Au nanoparticals was not changed.In addition,the current density?1.23 V vs.RHE?of Au@SiO₂/BiVO₄ in KHCO₃ was 3.27 mA cm^-2,increased by about 2.8 times than that in PBS,and the oxidation efficiency increased from 49%to 86%.It is because HCO₃-was involved in trapping photo-generated holes,further increasing the separation of photo-induced charges.2.Cu₂O was prepared by electrodeposition and the formation of Cu₂O film could be influenced by pH,deposition temperature and time.Crystal face of Cu₂O film can further affect the selectivity of reducing HMF into DHMF.The result showed that,the crystal face?111?could selectively reduce HMF into DHMF and the relative intensity of the crystal surface?220?and?110?enhanced could decrease the selectivity of DHMF.In addition,the presence of crystal face?220?,?110?and?110?could improve the conversion rate of HMF.Further regulating the pH,deposition temperature and time,we found that the electrode electrodeposited at pH7,60?and 30min,whose crystal face was?220?,?111?and corresponding peak intensity ratio was 1/0.76/0.74,the selectivity of DHMF was highest?59.7%?and the conversion rate of HMF was 76.9%.