Combined effect of bicarbonate and water in photosynthetic oxygen evolution and carbon neutrality

Carbon neutrality is widely concerned and highly valued by many countries.Biosphere has always maintained the balance between oxidized organic substances and assimilated organic matter,resulting in netzero carbon dioxide(CO_(2)) emissions and maintaining its own carbon neutrality.Nature has set a good example for human beings to coordinate oxygen(O_(2)) balance and CO_(2)balance,and achieve carbon neutrality.How does photosynthetic oxygen evolution initiate carbon and water neutrality?My synthesis shows that photo system Ⅱ functions as carbonic anhydrase to catalyze the reaction of CO_(2)hydration under physiological conditions,and CO_(2)hydration coupled with chemical equilibrium,H^(+)+HCO_(3)^(-)→1/2O_(2)+2e^(-)+2H^(+)+CO_(2),occurs in a photosystem Ⅱ corecomplex.Meanwhile,I focused on the revisiting of four classical heavy oxygen(O^(18)) labeling experiments and found that bicarbonate can promote photo synthetic oxygen evolution,and that photo synthetic oxygen evolution can alternately come from bicarbonate and water,not only water.Bicarbonate photolysis and water photolysis account for half of the photo synthetic oxygen evolution respectively,which can well explain the bicarbonate effect,Dole effect and plants’ environmental adaptability.Photosynthetic oxygen evolution initiated the journey of water metabolism and carbon metabolism in nature,which led to the coupling as 1:1(mol/mol) stoichiometric relationship between the reduction of CO_(2)and oxidation of organic carbon,coordinated the evolution of the atmosphere,hydrosphere,lithosphere and biosphere,and realized "carbon neutrality" in the whole Earth system.

Is bicarbonate directly used as substrate to participate in photosynthetic oxygen evolution

If the photosynthetic organisms assimilated only CO_(2) in the Archean atmosphere,hydroxide ion in the Archean seawater would not increase.If plants would not consume bicarbonate as a direct substrate during photosynthesis,it is difficult to explain the evolution of Earth's environment.To date,it is generally accepted that photosynthetic O_(2) evolution of plants come from water photolysis.However,it should be debated by evaluating the effect of bicarbonate in photosynthetic O_(2) evolution,analyzing the role of carbonic anhydrase(CA) in photosynthetic O_(2) evolution,and the relationship between thylakoid CA and photosynthetic O_(2) evolution.In the paper,I propose that bicarbonate is directly used as substrate to participate in photosynthetic O_(2) evolution.The rationality of bicarbonate photolysis of plants is discussed from the thermodynamics and evolution of Earth's environment.The isotopic evidence that bicarbonate is not the direct substrate of photosynthetic O_(2) release is reexamined,and the new explanation of bicarbonate photolysis in photosynthetic O_(2) evolution is proposed.

The InSe/g-CN van der Waals hybrid heterojunction as a photocatalyst for water splitting driven by visible light

Designing and developing the highly efficient photocatalysts is full of significance to achieve spontaneous photolysis water.In this work,using the first-principles calculations,we have performed a systematic theoretical study of water splitting photocatalytic activity of the InS e/g-CN heterojunction.It is concluded that the In Se/g-CN heterojunction is a typical type-II semiconductor,whose electrons and holes can be effectively separated.And the potential of the conduction band minimum(CBM)and valence band maximum(VBM)satisfy the requirements for photolysis water.Moreover,the changes of Gibbs free energy(ΔG)of the oxygen evolution reaction(OER)and the hydrogen evolution reaction(HER)are calculated to investigate thermodynamic sustainability of photolysis water.The results show that when pH=7,the potential driving force provided by the InSe/g-CN heterojunction can ensure the spontaneous progress of HER and OER.In addition,it is found that the solar conversion efficiency(η;)of the In Se/g-CN heterojunction is up to 13.7%,which indicates it has broad commercial application prospects.Hence,the In Se/g-CN heterojunction is expected to be an excellent candidate for photolysis water.