## 1 Introduction  
Increasing energy demand and the rapid depletion of fossil fuels have made it inevitable that renewable sources of alternative energy be found [1]. Despite the difficulties of finding alternative sources of energy, hydrogen has emerged as an excellent source of clean energy that could serve as a key technology for providing alternative energy [2]. The state-of-the-art high-efficiency hydrogen-producing catalysts are based on noble metals like Pt [3; 4; 5]. However, the cost and scarcity of noble metals are preventing hydrogen energy from being used in a variety of applications. Moreover, depletion of fossil fuels at a steady pace is contributing to the emerging energy crisis [6]. In this situation, hydrogen has become attractive as an excellent option for clean energy that could also serve as a key technology in providing sustainable alternative energy [7]. The discovery of photoelectrochemical water splitting using TiO\({}_{2}\) by [PERSON] and [PERSON] in 1972 has completely revolutionized the area of photoelectrochemical water splitting using semiconductor photoelectrodes [8]. In this regard, photoelectrochemical (PEC) water splitting to produce hydrogen is turning out to be a promising strategy through which energy produced from solar irradiation could be transformed and stored in the form of hydrogen [2; 9]. Photoelectrodes provide the essential function of converting solar energy-to-fuel. To achieve this conversion, the photoelectrode should possess a reasonable band gap for absorption of the incoming incident light. This is necessary to drive the reaction for the reduction and oxidation of water. The desired photoelectrode also has to provide charge transfer kinetics fast enough to minimize the recombination of oppositely charged ions at the electrode/electrolyte interface [9]. Metal oxides have larger bandgaps (higher than 2 eV) which restrains their light absorption capability and thereby makes them inefficient for solar energy conversion [10; 11; 12]. Among the various semiconductor materials that have been researched, p-type silicon (Si) stands out as a well-known photocathode owing to its excellent photoelectrochemical water splitting properties [13; 14; 15; 16]. Silicon is also an Earth-abundant semiconductor material with a narrow bandgap (1.12 eV). These qualities make it an appropriate material for absorbing a larger portion of the solar spectrum and thus an ideal candidate for the photovoltaic industry [17]. Even with these advantages, Si is quite unstable in aqueous conditions and in the absence of a catalyst, the reaction at the p-Si/electrolyte interface results in sluggish kinetics at zero overpotential (i.e., 0 V vs. RHE) [18]. One strategy to overcome this was to incorporate a corrosion-resistant protective layer that would minimize inhibition of the photogenerated carriers and thereby improve the charge transfer. Numerous studies have been carried out in the area of adding protective layers to Si photoelectrodes to improve the stability of p-Si photoelectrodes in aqueous conditions [19; 20; 21]. Platinum (Pt) [22] is well known for its use as an electrocataly in PEC hydrogen production. It is however, also a precious metal, the scarcity of which makes its large-scale deployment for PEC water splitting rather unlikely [23]. In response to these conditions, tremendous effort has been expended to find and develop Earth-abundant non-precious catalysts for hydrogen production. Recently, first-row transition-metal dichalcogenides have emerged as significant prospects for use in water-splitting reactions and been proposed as replacements for precious metals (i.e., Pt). This proposal is especially compelling due to their natural-abundance and high catalytic activity. Among these options, CoX\({}_{2}\) (X = S, Se) has lower overpotential with smaller Tafel slope and large exchange current and variants have shown promising development in HER (hydrogen evolution reaction) reactions [24; 25; 26]. [PERSON] et al.