The development of nontoxic and stable all-inorganic perovskite nanocrystals (NCs) represents a major challenge to unlock widely practical applications in photoelectric fields.

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Exploiting robust and durable electrocatalysts for water splitting remains a challenge due to its sluggish oxidative half reaction. Herein, we demonstrate a facile and novel strategy to prepare an amorphous N-doped cobalt borophosphate catalyst through the calcination of zeolite-type cobalt borophosphate precursor with NH3 molecule. The as-prepared material displays robust catalytic activity and high stability within 18 h for the oxygen evolution reaction (OER) in 1.0 M KOH, e.g., an overpotential of 276 mV at 10 mA cm–2 (η @ 10 mA cm–2) and a Tafel slope of 55.8 mV dec–1, which is comparable to that of the benchmark IrO2 electrocatalyst. Its excellent catalytic activity should be ascribed to the N-dopant which could accelerate the electron transfer by tuning the electronic structure of this borophosphate; moreover, this amorphous phase with zeolite-like porous structures could increase its active site density and improve the electron and mass transport as well as facilitating gas release. Our study not only discovers a high-efficiency OER electrocatalyst but also provides a facile and practical pathway to develop promising electrocatalysts for water splitting.

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This study aims to analyze massive data in cities through data vitalization, and quantitatively evaluate smart city services, so as to promote the construction and development of smart cities. Due to the great difference between cities, a single evaluation method cannot accurately describe the development of a city. In this study, we classify cities by multiple labels according to various bases to give cities comprehensive description. Then, a Multi-level Service Evaluation System (MSES) is introduced. It considers individual weights to cities with different characteristics and evaluates the smart city services from different aspects. In addition to putting forward the iterative development of smart city services, a Maturity Model-based Service Evaluation (MMSE) framework is proposed based on the evaluation results of the MSES. It constructs a standardized and high confident evaluation framework to analyze the current state of cities and make feedback to the government policies. Finally, we take 10 cities in China to demonstrate the effectiveness of MMSE during the development of smart city services.

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