| The advent of the"Internet of Things"and 5G era has promoted the development of portable and wearable devices.However,the energy supply for low-power electronics is confronted with problems such as environmental pollution introduced by excessive consumption of batteries and complicated operation of sophisticated rechargeable electronic devices.To address the above issues,researchers have paid increasingly attention to harvesting low-grade energy in the environment to power low-power electronics,which is not only able to solve energy supply problems,but also to provide an alternative choice in a simple way under extreme environments.Among the many environmental low-grade energy harvesting technologies,the air humidity energy harvesting power generation technology based on the electrokinetic theory has attracted more and more attention due to its strong adaptability and wide energy sources.Nevertheless,there are still some problems that need to be solved urgently for air humidity energy harvesting power generation technology,such as high material costs,complicated fabrication process,requirement for high humidity,short lifespan,and so on.Waste biomass carbon is cost-effective,abundant,and available in daily life and industry,which makes it an ideal raw material for electricity generator.For the first time,the performance of moisture power generation of biomass was investigated,followed by exploring the mechanism of power generation.Further,the waste biomass is applied for the design of electricity generator for harvesting energy from environmental moisture.The paper-based moisture power generator was developed to verify the feasibility of generating electricity via air humidity.Through the combination of commercial carbon ink and air-laid paper,a piece of paper of 6 cm~2 continuously generated a voltage of 0.35 V and a current of 35.9μA at 20℃and a relative humidity(RH)of 60%,which was stable for more than 120h.Li Cl solution(5M)was utilized as an alternative of deionized water,which effectively enhanced the output voltage and stabilization time.Quantitative research shown that there is a coupling relationship between temperature,humidity,and salt concentration.By connecting generators in series and parallel,low-power devices such as electronic calculators,LED lights,and electronic watches have been successfully powered.The working mechanism of the humidity generator is investigated through characterization,control experiments,and theoretical calculations.The Li Cl on one end of the paper-based humidity power generator is able to capture moisture from air,which creates a moisture gradient on the paper.Also,hydronium ions can be introduced by the interaction between moisture and oxygen-containing functional groups(-OH,-COOH,etc.)on the ink carbon.The voltage and current are produced by directional migration of hydronium ions through moisture gradient on paper via capillary action.By increasing the oxygen-containing functional group,the voltage can be effectively increased,providing more possibilities for future practical applications.The feasibility of other waste biomass materials on humidity power generation was also investigated based on the working mechanism of the humidity generator.A wood-based humidity power generator(5 cm~2)was designed and it generated an output voltage of 0.31 V and a current of 86.5μA for more than 60 h by dropping Li Cl solution(3 M)on one end of the wood chip.The wood-based humidity power generator can also generate electricity in moist soil,making it stably generate voltage in the absence of hygroscopic salt.When the soil humidity was 50%,the wood-based humidity power generator can provide an output voltage of0.16 V and current of 40.28μA(20°C,RH 60%),which can power a LCD screen with the assistance of capacitors.The electricity generator based on waste biomass and ink with its feasibility for power generation in multiple environments will greatly expand the application of low-power and portable devices. |
