Hydrovoltaic Performance Research Of Wood Biogenic Material And Its Modification

The phenomenon that the direct conversion of water energy into electric energy by the interaction between materials and fluids is called hydrovoltaic effect.As a novel way to convert low quality internal energy into electric energy,hydrovoltaic has been widely concerned in the past decade.Meeting the composition and structure requirement of the generation of hydrovoltaic effect,wood biogenic materials with rich active carbon surface and natural directional porous structure shows great application potential in the field of hydrovoltaic conversion.Therefore,this paper intends to develop and study wood biogenic carbon hydrovoltaic materials.Firstly,the influence of the structure and composition of wood pyrolytic product on the hydrovoltaic effect was studied,and the relationship was clarified;On this basis,the structure of pyrolytic carbon was improved by graphitization,and the induced current was optimized;at the same time,nano-mastoid structures were constructed in the wood porous carbon to further optimize the hydrovoltaic performance by forming “ratchet wheel” effect.The research contents and conclusions are listed as follows:(1)The effects of the structure and composition on the hydrovoltaic properties of wood biogenic materials with directional micron pore structure were studied by carbonization at different temperatures.The results shown that,when the heat treatment temperature at 500 ℃,organic intermediates and polyaromatic compounds were mainly formed in the pyrolysis product of wood,at 600 ℃,amorphous carbon was formed,and pyrolytic product was basically converted to amorphous carbon when the carbonization temperature at 800 ℃ and 1000 ℃.Based on the double electric layer effect and electron drag mechanism,effective carrier migration formed in amorphous carbon under the flow induction,which is the key to affect the hydrovoltaic of wood biogenic materials.CW800 and CW1000 samples obtained by heat treatment at 800 ℃ and 1000 ℃ respectively showed the optimal open circuit water voltage(0.27 V)and the optimal short-circuit water current(1.1 μA).(2)Based on the porous carbon of wood,the graphitized modified wood porous carbon hydrovoltaic materials was obtained by transition metal catalytic technology to change the structure of wood pyrolysis carbon,and the formed graphitized structure was used to optimize the hydrovoltaic short-circuit current of the material.The relationships between the microstructure,crystal structure,chemical composition and graphitization degree of the materials and the hydrovoltaic performance was systematically studied,and the influence mechanism of graphitization process on the hydrovoltaic effect was analyzed.The results shown that the graphite nanoribbons were formed in the wood biogenic carbon by introduction of transition metal Ni,and the graphitization degree of wood porous carbon increased with the rising of the catalyst.The graphitization modification process shown dual influences on the hydrovoltaic effect of wood porous carbon.Suitable graphitized modification can improve carrier migration density and migration rate,which increased the open-circuit voltage and greatly optimized induced current,and excessive graphitized modification caused internal charge dissipation,which made it difficult for carriers to accumulate and reduced the hydrovoltaic performance.The optimal open-circuit voltage and short-circuit current of the graphitized wood porous carbon reached 0.49 V and 35 μA,short-circuit current of the graphitized wood porous carbon was 32 times higher than that of the unmodified wood porous carbon.(3)On the basis of(2),the preparation process was adjusted to retain the nanostructure of transition metal catalyst,and nano papillae were constructed in situ in the microntube of wood porous carbon and obtained the wood porous carbon modified with nano papillae to optimize the hydrovoltaic performance through “ratchet wheel”effect.The results of research shown that the presence of transition metal Ni can induce the formation of a large number of typical core-shell nano-mastoid structures with diameter of about 100 nm,and Ni nanoparticles as core layer and graphitized carbon as shell layer.The results of fluid flow field simulation shown that the nano-mastoid structure has little effect on the flow velocity distribution due to its small particle size.Compared with the unmodified sample,the hydrovoltaic effect of wood porous carbon modified by nano mastoid process was lower,which may due to the presence of a large number of Ni nanoparticles as “electron traps” that infulenced the carrier migration and accumulation,resulting in a decrease in its hydrovoltaic performance.