Electrocatalytic Study On Natural DNA-Based Doped Carbons And The Composites

Hydrogen energy has attracted global attention due to its high energy density,cleanliness and no pollution.Overall water splitting（OWS）is a promising method for commercial hydrogen production,but the sluggish kinetics of the anodic oxygen evolution reaction（OER）results in 90%of the electricity consumption in water electrolysis.Hydrazine oxidation reaction（Hz OR）is expected to replace the slow OER due to its lower standard reaction potential and faster reaction kinetics,and coupling Hz OR with HER,can form an overall hydrazine splitting（OHz S）system.The oxygen reduction reaction（ORR）is the cathodic reaction in fuel cells and zinc-air batteries,but the kinetic rate of cathodic ORR is slower than that of the anodic reaction.Pt-based materials have excellent electrocatalytic activities for HER,ORR,and Hz OR,but their large-scale applications are limited due to their disadvantages of high cost and low reserves.The search for HER,ORR,and Hz OR catalysts that can replace Pt-based catalysts has become hotspots in recent years.In this paper,using natural DNA as precursor for the first time,different methods were used to synthesize doped carbons and the composite materials with excellent performance for HER,ORR and Hz OR.The main research contents and conclusions are as follows:1.Natural DNA-derived highly-graphitic N,P,S-tridoped carbon nanosheets for multiple electrocatalytic applicationsUsing natural DNA and thiourea as precursors,high-quality N,P,S-tridoped carbon nanosheets with high degree of graphitization,large surface area,and uniform doping were prepared by simple mixing and pyrolysis,showing excellent ORR and HER activities.The ORR half-wave potential（0.88 V）in the alkaline electrolyte is better than that of Pt/C（0.86 V）,together with good acidic ORR performance.The basic and acidic HER only requires overpotentials of 129 m V and 170 m V,respectively,to reach 10 m A cm^-2.Density functional theory（DFT）calculations show that the active site for the ORR process is the C atom adjacent to the S atom（C_S）,and the active site for the HER process is the P atom.The assembled rechargeable Zn-air battery exhibits comparable open-circuit voltage,peak power density,specific capacity,and excellent charge-discharge stability to Pt/C.2.Natural DNA-assisted ultrafine Fe P embedded in N,P-codoped carbons for electrocatalytic applicationsUsing natural DNA and Fe SO₄·7H₂O as precursors,Fe P/N,P-codoped carbon composites（Fe P/NPC-DNA）with large surface area,high graphitization,and ultrafine Fe P nanoparticles（less than 10 nm）embedded were constructed and exhibits excellent ORR and HER bifunctional electrocatalytic performance.The half-wave potential of Fe P/NPC-DNA in alkaline ORR of electrolyte is 0.87 V,which is better than that of Pt/C,together with excellent anti-poisoning ability and good alkaline HER performance.DFT calculations unambiguously revealed that the active sites for the bifunctional activity of ORR and HER are C atoms adjacent to N（C_N）and P atoms,respectively.Density of states and differential charge density calculations reveal that the interaction between Fe P and NPC can facilitate interfacial electron transfer,thereby optimizing the adsorption/desorption strength of the intermediate.The assembled rechargeable Zn-air battery exhibits larger specific capacity,energy density,and better charge-discharge stability than Pt/C.3.Natural DNA-derived Ir-Ir₂P in porous N,P-codoped carbon for efficient hydrogen production assisted by hydrazine oxidationUsing natural DNA and Ir Cl₃·3H₂O as precursors and 15 nm SiO₂ spheres as template,Ir-Ir₂P/porous N,P-codoped carbon materials（Ir/PNPC）with large surface area,high crystallinity and high doping quality were constructed through mixing,pyrolysis and etching.The Ir/PNPC exhibits excellent bifunctional HER and Hz OR activities surpassing commercial Pt/C in alkaline,neutral and acidic conditions.Compared with the OWS system,the required voltage at the same current density is effectively reduced in the OHz S system.The assembled direct hydrazine/H₂O₂ fuel cell has an open-circuit voltage of 1.68V and a power density of 111.0 m W cm^-2,and its driven OHz S system achieves a hydrogen production rate of 30.5 m L h^-1(1.245 mmol h^-1).