Yiming Chen,Wenquan Gu,Li Tan,Zhimin Ao,Taicheng An,Shaobin Wang
Photocatalytic H 2 O 2 production by O 2 reduction is an environmental-friendly process for solar light conversion to chemical energy. In this work, Ti 3 C 2 MXene was used as a non-noble metal cocatalyst to load on P25 as Ti 3 C 2 /TiO 2 (TC/TO) photocatalysts for photocatalytic H 2 O 2 synthesis. A H 2 O 2 formation rate (179.7 μmol L −1 h −1 ) of the optimized 10 %-TC/TO composite was obtained to be over 21 folds as high as that of P25 under UV light. Radical quenching experiments and superoxide radical detection confirmed the superoxide radical as the primary intermediate, suggesting the O 2 reduction in two-step single-electron indirect reaction. The higher activity of TC/TO can be attributed to the functions of Ti 3 C 2 MXene in accelerating the separation and transfer of photogenerated electron-hole pairs, suppressing their recombination, and blocking the surface Ti OOH formation. This work proves the promising roles of Ti 3 C 2 MXene in the photocatalytic reaction and further expands their new applications in photocatalysis .
Photocatalytic H 2 O 2 production is an eco-friendly technique because only H 2 O, molecular O 2 and light are involved. However, it still confronts the challenges of the unsatisfactory productivity of H 2 O 2 and the dependence on organic electron donors or high purity O 2 , which restrict the practical application. Herein, we construct a type-II heterojunction of the protonated g-C 3 N 4 coated Co 9 S 8 semiconductor for photocatalytic H 2 O 2 production. The ultrathin g-C 3 N 4 uniformly spreads on the surface of the dispersed Co 9 S 8 nanosheets by a two-step method of protonation and dip-coating, and exhibits improved photogenerated electrons transportability and e - -h + pairs separation ability. The photocatalytic system can achieve a considerable productivity of H 2 O 2 to 2.17 mM for 5 h in alkaline medium in the absence of the organic electron donors and pure O 2 . The optimal photocatalyst also obtains the highest apparent quantum yield (AQY) of 18.10% under 450 nm of light irradiation, as well as a good reusability. The contribution of the type-II heterojunction is that the migrations of electrons and holes within the interface between g-C 3 N 4 and Co 9 S 8 matrix promote the separation of photocarriers, and another channel is also opened for H 2 O 2 generation. The accumulated electrons in conduction band (CB) of Co 9 S 8 contribute to the major channel of two-electron reduction of O 2 for H 2 O 2 production. Meanwhile, the electrons in CB of g-C 3 N 4 participate in the single electron reduction of O 2 as an auxiliary channel to enhance the H 2 O 2 production.
Yu Wang,Yuxin He,Yujing Chi,Peiji Yin,Lishan Wei,Wenwen Liu,Xinyao Wang,Han Zhang,Haiyan Song
Photocatalytic H 2 O 2 production is a green and sustainable technology, which still exposes the issues of excessive dependence on organic electron donors and pure O 2 , and lacking effective use. It is necessary to develop more efficient and more economical photocatalysis system for H 2 O 2 production. Here, we construct a S-scheme p-n heterojunction from the p-type MnS and the n-type protonated g-C 3 N 4 (PCN) semiconductors for photocatalytic H 2 O 2 production and achieve the in situ use of H 2 O 2 for oxidative degradation of oxytetracycline (OTC). The PCN/MnS composite synthesized by a one-step method well maintains a nanosphere structure of α-MnS and load the PCN on the sphere surface to form a heterojunction with strong interaction. PCN/MnS exhibits the improved photogenerated charge separation and electron transfer efficiency. An optimal photocatalyst can produce 669.6 μM of H 2 O 2 for 6 h without using the electron donors and the pure O 2 gas. The mechanism proposed the contribution of a S-scheme p-n heterojunction forms between PCN and MnS. The electrons in conduction band (CB) of MnS are responsible for the major single-electron reduction of •O 2 - radicals and the auxiliary two-electron reduction of O 2 for H 2 O 2 production, while the holes in valence band (VB) of PCN further promote the separation of photocarriers. The photogenerated H 2 O 2 can be effectively used as an in-situ oxidant to achieve 82.2% degradation of OTC in water within 80 min. The •O 2 - radicals which originate from the in situ decomposition of H 2 O 2 over PCN/MnS mainly contribute to the OTC oxidation .
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