Volatility of commodity prices has affected dramatically the coffee industry in recent years, particularly small holder farmers. Differentiation of coffee through certification, such as sustainahility and quality attr...Volatility of commodity prices has affected dramatically the coffee industry in recent years, particularly small holder farmers. Differentiation of coffee through certification, such as sustainahility and quality attributes, has been proposed as a strategy for protection of the farmers against volatility in the international prices. This research paper evaluated three different models to explore the effectiveness of the differentiation strategies in protecting the farmer against price volatility in recent years, focusing on the case of Costa Rica. Evidence showed important differences in the price dynamics over time when comparing three groups of coffee.展开更多
Utilizing sunlight as a renewable energy source,photocatalysis offers a potential solution to global warming and energy shortages by converting CO_(2) into useful solar fuels,including CO,CH4,CH3OH,and C2H5OH.Among th...Utilizing sunlight as a renewable energy source,photocatalysis offers a potential solution to global warming and energy shortages by converting CO_(2) into useful solar fuels,including CO,CH4,CH3OH,and C2H5OH.Among the various formulations investigated,copper-based photocatalysts stand out as particularly appealing for CO_(2) conversion due to their cost-effectiveness and higher abundance in comparison to catalysts based on precious metals.This literature review provides a thorough summary of the latest developments in copper-based photocatalysts used for CO_(2) reduction reactions,including metallic copper,copper oxide,and cuprous oxide photocatalysts.The review also provides a categorical summary of the CO_(2) reduction products and a detailed categorical discussion of the means of modulation and modification of each copper-based catalyst.Finally,this review highlights the existing challenges and proposes future research directions in the development of copper-based photocatalysts for CO_(2) reduction,focusing on boosting energy utilization and improving product formation rates.展开更多
Developing highly efficient,cost-effective,and stable electrocatalysts for hydrogen evolution reaction(HER)is of considerable importance but remains challenging.Herein,we report the fabrication of a robust Ru-based el...Developing highly efficient,cost-effective,and stable electrocatalysts for hydrogen evolution reaction(HER)is of considerable importance but remains challenging.Herein,we report the fabrication of a robust Ru-based electrocatalyst,which comprises heterostructured Ru-Ru_(2)P nanoparticles that are embedded in the N,P-codoped carbon nanofibers(CNFs),through a synthetic strategy involving electrospinning and temperature-controlled pyrolysis treatment.The as-prepared Ru-Ru_(2)P catalyst(Ru-Ru_(2)P@CNFs)shows excellent HER catalytic activities with low overpotentials of 11 and 14 mV in acidic and alkaline media,respectively,to achieve a current density of 10 mA cm^(−2),which are superior to the individual components of pure Ru and Ru_(2)P catalysts.Density functional theory calculations demonstrate the existence of electronic coupling effect between Ru and Ru_(2)P at the heterointerfaces,leading to a well-modulated electronic structure with optimized hydrogen adsorption strength and enhanced electrical conductivity for efficient HER electrocatalysis.In addition,the overall synthetic strategy can be generalized for the synthesis of a series of transitional metal phosphide-based nanofibers,thereby holding a remarkable capacity for various potential applications.展开更多
文摘Volatility of commodity prices has affected dramatically the coffee industry in recent years, particularly small holder farmers. Differentiation of coffee through certification, such as sustainahility and quality attributes, has been proposed as a strategy for protection of the farmers against volatility in the international prices. This research paper evaluated three different models to explore the effectiveness of the differentiation strategies in protecting the farmer against price volatility in recent years, focusing on the case of Costa Rica. Evidence showed important differences in the price dynamics over time when comparing three groups of coffee.
文摘Utilizing sunlight as a renewable energy source,photocatalysis offers a potential solution to global warming and energy shortages by converting CO_(2) into useful solar fuels,including CO,CH4,CH3OH,and C2H5OH.Among the various formulations investigated,copper-based photocatalysts stand out as particularly appealing for CO_(2) conversion due to their cost-effectiveness and higher abundance in comparison to catalysts based on precious metals.This literature review provides a thorough summary of the latest developments in copper-based photocatalysts used for CO_(2) reduction reactions,including metallic copper,copper oxide,and cuprous oxide photocatalysts.The review also provides a categorical summary of the CO_(2) reduction products and a detailed categorical discussion of the means of modulation and modification of each copper-based catalyst.Finally,this review highlights the existing challenges and proposes future research directions in the development of copper-based photocatalysts for CO_(2) reduction,focusing on boosting energy utilization and improving product formation rates.
基金financially supported by the Natural Science Foundation of Zhejiang Province (LQ20B030001 and LY20E020002)China Postdoctoral Science Foundation (2021M702305)。
文摘Developing highly efficient,cost-effective,and stable electrocatalysts for hydrogen evolution reaction(HER)is of considerable importance but remains challenging.Herein,we report the fabrication of a robust Ru-based electrocatalyst,which comprises heterostructured Ru-Ru_(2)P nanoparticles that are embedded in the N,P-codoped carbon nanofibers(CNFs),through a synthetic strategy involving electrospinning and temperature-controlled pyrolysis treatment.The as-prepared Ru-Ru_(2)P catalyst(Ru-Ru_(2)P@CNFs)shows excellent HER catalytic activities with low overpotentials of 11 and 14 mV in acidic and alkaline media,respectively,to achieve a current density of 10 mA cm^(−2),which are superior to the individual components of pure Ru and Ru_(2)P catalysts.Density functional theory calculations demonstrate the existence of electronic coupling effect between Ru and Ru_(2)P at the heterointerfaces,leading to a well-modulated electronic structure with optimized hydrogen adsorption strength and enhanced electrical conductivity for efficient HER electrocatalysis.In addition,the overall synthetic strategy can be generalized for the synthesis of a series of transitional metal phosphide-based nanofibers,thereby holding a remarkable capacity for various potential applications.
