The dissociation of H2O molecules plays an important role in producing protons for promoting hydrogenation reduction of CO2. Therefore, developing excellent photocatalysts to promote the dissociation of H2O molecules and reveal the effect mechanism is the key research direction to enhance CO2 reduction efficiency. In this work, we synthesized BiSbO4 with oxygen vacancies (OVs) to investigate the photocatalytic mechanism of CO2 conversion and H2O dissociation. Experimental results indicate that the introduction of OVs into BiSbO4 can enhance the absorption capacity of light, narrowing band gaps and impeding the recombination of photogenerated carriers. Importantly, the existence of OVs in BiSbO4 can promote the adsorption and activation of H2O molecules via the stronger covalent interaction, which facilitates the dissociation of H2O molecules to generate more protons and lowers the energy barriers of •COOH to improve the efficiency of CO2 reduction. This study reinforces our understanding of the principle of photocatalytic CO2 reduction and the important role of H2O dissociation in photocatalytic CO2 conversion.
Liu Yang,Haoxiang Xu,Huibing Liu,Daojian Cheng,Dapeng Cao
Developing efficient non-precious bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is highly critical for overall water splitting. Herein, vertically aligned CoTe and NiTe nanoarrays are synthesized in situ grown on Ni foams (marked as CoTeNR/NF and NiTeNR/NF) via a facile hydrothermal method, and further explore their catalytic activities for overall water splitting. The CoTeNR/NF catalyst exhibits not only excellent OER performance with a low overpotential of 350 mV to deliver 100 mA cm −2 , but also high HER activity only requiring 202 mV overpotential to yield 10 mA cm −2 in alkaline condition. Moreover, experimental technique and density functional theory are combined together to reveal that the real active sites of CoTeNR/NF for OER are from the in situ generated CoOOHspecies on CoTeNR/NF in the OER process, and also propose a new HER performance evaluation criteria of using H 2 O adsorption energy, H 2 O dissociation barrier, and H 2 /OH − desorption energy as an indicator. The new criteria can satisfactorily evaluate the HER performance of as-synthesized samples, while the traditional one of using H adsorption energy as an indicator fails in the HER performance evaluation of as-synthesized samples. It is expected that the new evaluation criteria can be used as a general criteria to evaluate the HER performance of other electrocatalysts.
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