Hydrogen evolution via noble metals based photocatalysts: A review

In recent decades, the use of photocatalysts in the evolution of hydrogen (H2) has received much attention. However, the use of the well-known titanium oxide and another photocatalyst as a base for noble metals is limited due to their major weakness in electron-hole pair separation. The use of cocatalysts can be a good way to overcome this problem and provide better performance for the evolution of hydrogen. In this review, suitable high-efficiency cocatalysts for solar hydrogen production have been thoroughly reviewed. New strategies and solutions were examined in terms of increasing the recombination of charge carriers, designing reactive sites, and enhancing the wavelengths of light absorption. Several new types of cocatalysts based on semiconductors in noble groups and dual metals have been evaluated. It is expected that these photocatalysts will be able to reduce the activation energy of reaction and charge separation. In this regard, the existing views and challenges in the field of photocatalysts are presented. The characteristics of monoatomic photocatalysts are reviewed in this manuscript and the latest advances in this field are summarized. Further, the future trends and upcoming research are also briefly discussed. Finally, this review presents noble metal-based photocatalysts for providing suitable photocatalysts on a larger scale and improving their applicability.

Recent Progress and Approaches on Transition Metal Chalcogenides for Hydrogen Production

Development of efficient and affordable photocatalysts is of great significance for energy production and environmental sustainability. Transition metal chalcogenides (TMCs) with particle sizes in the 1–100 nm have been used for various applications such as photocatalysis, photovoltaic, and energy storage due to their quantum confinement effect, optoelectronic behavior, and their stability. In particular, TMCs and their heterostructures have great potential as an emerging inexpensive and sustainable alternative to metal-based catalysts for hydrogen evolution. Herein, the methods used for the fabrication of TMCs, characterization techniques employed, and the different methods of solar hydrogen production by using different TMCs as photocatalyst are reviewed. This review provides a summary of TMC photocatalysts for hydrogen production.

THEORETICAL AND EXPERIMENTAL INVESTIGATION OF ESTIMATING CHANGE POINT IN MULTIVARIATE PROCESSES VIA SIMULTANEOUS COVARIANCE MATRIX AND MEAN VECTOR

The identification of change points in statistical process control (SPC) data is the critical criterion for multivariate techniques when output is out-of-control condition. Therefore, monitoring all independent variables is essential and demands targeted attention to avoid errors at the systems control stage. However, estimating change-point in multivariate control charts is the main problem when these correlated quality characteristics monitor together. Therefore, we proposed a combination of an ensemble learning-based model of artificial neural networks with support vector machines to monitor process mean vector and covariance matrix shifts simultaneously to estimate the change point in a multivariable system. The performance of the final model indicated an estimated changing point with one sample over 6,000 simulated cases with a probability of 98 percent, which is a significantly high accuracy rating. Finding suggests the outcome of the project confirms that the proposed model can provide a precise estimating the change point by monitoring the mean vector and the covariance matrix simultaneously and, helps to identify those variable(s) responsible for an out-of-control condition. For further validation of the model, the performance of the proposed model has been compared with previous reported which confirms a better performance of the proposed model. Finally, the model was applied to monitor the performance of the solar hydrogen production system and the model identify the variables which have negative effects on the performance of the system.